[V14,3/5] i2c: tegra: Add DMA support

Message ID 1549480569-24860-3-git-send-email-skomatineni@nvidia.com
State Changes Requested
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  • [V14,1/5] i2c: tegra: sort all the include headers alphabetically
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Commit Message

Sowjanya Komatineni Feb. 6, 2019, 7:16 p.m.
This patch adds DMA support for Tegra I2C.

Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
transfer size of the max FIFO depth and DMA mode is used for
transfer size higher than max FIFO depth to save CPU overhead.

PIO mode needs full intervention of CPU to fill or empty FIFO's
and also need to service multiple data requests interrupt for the
same transaction. This adds delay between data bytes of the same
transfer when CPU is fully loaded and some slave devices has
internal timeout for no bus activity and stops transaction to
avoid bus hang. DMA mode is helpful in such cases.

DMA mode is also helpful for Large transfers during downloading or
uploading FW over I2C to some external devices.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
---
 [V14] : Switched back to use dma_alloc_coherent as it guarentees contiguous device
	 dma address space.
	 Fixed FIFO Trigger level programming to construct value from scratch.
	 Previous versions does register read-modify-write without masking.
	 T20 has DVC offsets different to I2C. This version has fix to account DVC
	 offset during dma slave configuration.
 [V13] : T20 has DVC used for some power controls. This version has fix for using
	 proper DVC register offsets for DMA programming incase when used in DMA
	 mode.
 [V12] : Replaced dma_alloc_coherent with dma_alloc_attrs to force the allocated
	 buffer to be contiguous also in physical memory as Tegra194 supports max
	 64K and dma_alloc_coherent doesnt guarentee contiguous memory.
	 Changed return code from EIO to EINVAL incase of failure to obtain dma
	 descriptor.
	 Fixed coding style check issues.	 
 [V11] : Replaced deprecated dmaengine_terminate_all with dmaengine_termine_async
	 from non-atomic context and dmaengine_terminate_sync from atomic context.
	 Fixed to program fifo trigger levels properly when transfer falls back to
	 pio mode in case of dma slave configuration failure and other minor fixes.
 [V10] : APBDMA is replaced with GPCDMA on Tegra186 and Tegra194 designs.
	 Added apbdma hw support flag to now allow Tegra186 and later use
	 APBDMA driver.
	 Added explicit flow control enable for DMA slave config and error handling.
	 Moved releasing DMA resources to seperate function to reuse in
	 multiple places.
	 Updated to register tegra_i2c_driver from module level rather than subsys
	 level.
	 Other minor feedback
 [V9] :  Rebased to 5.0-rc4
	 Removed dependency of APB DMA in Kconfig and added conditional check
 	 in I2C driver to decide on using DMA mode.
	 Changed back the allocation of dma buffer during i2c probe.
	 Fixed FIFO triggers depending on DMA Vs PIO.
 [V8] :  Moved back dma init to i2c probe, removed ALL_PACKETS_XFER_COMPLETE
	 interrupt and using PACKETS_XFER_COMPLETE interrupt only and some
	 other fixes
	 Updated Kconfig for APB_DMA dependency
 [V7] :  Same as V6
 [V6] :  Updated for proper buffer allocation/freeing, channel release.
	 Updated to use exact xfer size for syncing dma buffer.
 [V5] :  Same as V4
 [V4] :  Updated to allocate DMA buffer only when DMA mode.
	 Updated to fall back to PIO mode when DMA channel request or
	 buffer allocation fails.
 [V3] :  Updated without additional buffer allocation.
 [V2] :  Updated based on V1 review feedback along with code cleanup for
	 proper implementation of DMA.


 drivers/i2c/busses/i2c-tegra.c | 411 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 367 insertions(+), 44 deletions(-)

Comments

Thierry Reding Feb. 7, 2019, 11:01 a.m. | #1
On Wed, Feb 06, 2019 at 11:16:07AM -0800, Sowjanya Komatineni wrote:
> This patch adds DMA support for Tegra I2C.
> 
> Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
> transfer size of the max FIFO depth and DMA mode is used for
> transfer size higher than max FIFO depth to save CPU overhead.
> 
> PIO mode needs full intervention of CPU to fill or empty FIFO's
> and also need to service multiple data requests interrupt for the
> same transaction. This adds delay between data bytes of the same
> transfer when CPU is fully loaded and some slave devices has
> internal timeout for no bus activity and stops transaction to
> avoid bus hang. DMA mode is helpful in such cases.
> 
> DMA mode is also helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
>  [V14] : Switched back to use dma_alloc_coherent as it guarentees contiguous device
> 	 dma address space.
> 	 Fixed FIFO Trigger level programming to construct value from scratch.
> 	 Previous versions does register read-modify-write without masking.
> 	 T20 has DVC offsets different to I2C. This version has fix to account DVC
> 	 offset during dma slave configuration.
>  [V13] : T20 has DVC used for some power controls. This version has fix for using
> 	 proper DVC register offsets for DMA programming incase when used in DMA
> 	 mode.
>  [V12] : Replaced dma_alloc_coherent with dma_alloc_attrs to force the allocated
> 	 buffer to be contiguous also in physical memory as Tegra194 supports max
> 	 64K and dma_alloc_coherent doesnt guarentee contiguous memory.
> 	 Changed return code from EIO to EINVAL incase of failure to obtain dma
> 	 descriptor.
> 	 Fixed coding style check issues.	 
>  [V11] : Replaced deprecated dmaengine_terminate_all with dmaengine_termine_async
> 	 from non-atomic context and dmaengine_terminate_sync from atomic context.
> 	 Fixed to program fifo trigger levels properly when transfer falls back to
> 	 pio mode in case of dma slave configuration failure and other minor fixes.
>  [V10] : APBDMA is replaced with GPCDMA on Tegra186 and Tegra194 designs.
> 	 Added apbdma hw support flag to now allow Tegra186 and later use
> 	 APBDMA driver.
> 	 Added explicit flow control enable for DMA slave config and error handling.
> 	 Moved releasing DMA resources to seperate function to reuse in
> 	 multiple places.
> 	 Updated to register tegra_i2c_driver from module level rather than subsys
> 	 level.
> 	 Other minor feedback
>  [V9] :  Rebased to 5.0-rc4
> 	 Removed dependency of APB DMA in Kconfig and added conditional check
>  	 in I2C driver to decide on using DMA mode.
> 	 Changed back the allocation of dma buffer during i2c probe.
> 	 Fixed FIFO triggers depending on DMA Vs PIO.
>  [V8] :  Moved back dma init to i2c probe, removed ALL_PACKETS_XFER_COMPLETE
> 	 interrupt and using PACKETS_XFER_COMPLETE interrupt only and some
> 	 other fixes
> 	 Updated Kconfig for APB_DMA dependency
>  [V7] :  Same as V6
>  [V6] :  Updated for proper buffer allocation/freeing, channel release.
> 	 Updated to use exact xfer size for syncing dma buffer.
>  [V5] :  Same as V4
>  [V4] :  Updated to allocate DMA buffer only when DMA mode.
> 	 Updated to fall back to PIO mode when DMA channel request or
> 	 buffer allocation fails.
>  [V3] :  Updated without additional buffer allocation.
>  [V2] :  Updated based on V1 review feedback along with code cleanup for
> 	 proper implementation of DMA.
> 
> 
>  drivers/i2c/busses/i2c-tegra.c | 411 ++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 367 insertions(+), 44 deletions(-)

Acked-by: Thierry Reding <treding@nvidia.com>
Dmitry Osipenko Feb. 7, 2019, 1:57 p.m. | #2
06.02.2019 22:16, Sowjanya Komatineni пишет:
> This patch adds DMA support for Tegra I2C.
> 
> Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
> transfer size of the max FIFO depth and DMA mode is used for
> transfer size higher than max FIFO depth to save CPU overhead.
> 
> PIO mode needs full intervention of CPU to fill or empty FIFO's
> and also need to service multiple data requests interrupt for the
> same transaction. This adds delay between data bytes of the same
> transfer when CPU is fully loaded and some slave devices has
> internal timeout for no bus activity and stops transaction to
> avoid bus hang. DMA mode is helpful in such cases.
> 
> DMA mode is also helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---
>  [V14] : Switched back to use dma_alloc_coherent as it guarentees contiguous device
> 	 dma address space.
> 	 Fixed FIFO Trigger level programming to construct value from scratch.
> 	 Previous versions does register read-modify-write without masking.
> 	 T20 has DVC offsets different to I2C. This version has fix to account DVC
> 	 offset during dma slave configuration.
>  [V13] : T20 has DVC used for some power controls. This version has fix for using
> 	 proper DVC register offsets for DMA programming incase when used in DMA
> 	 mode.
>  [V12] : Replaced dma_alloc_coherent with dma_alloc_attrs to force the allocated
> 	 buffer to be contiguous also in physical memory as Tegra194 supports max
> 	 64K and dma_alloc_coherent doesnt guarentee contiguous memory.
> 	 Changed return code from EIO to EINVAL incase of failure to obtain dma
> 	 descriptor.
> 	 Fixed coding style check issues.	 
>  [V11] : Replaced deprecated dmaengine_terminate_all with dmaengine_termine_async
> 	 from non-atomic context and dmaengine_terminate_sync from atomic context.
> 	 Fixed to program fifo trigger levels properly when transfer falls back to
> 	 pio mode in case of dma slave configuration failure and other minor fixes.
>  [V10] : APBDMA is replaced with GPCDMA on Tegra186 and Tegra194 designs.
> 	 Added apbdma hw support flag to now allow Tegra186 and later use
> 	 APBDMA driver.
> 	 Added explicit flow control enable for DMA slave config and error handling.
> 	 Moved releasing DMA resources to seperate function to reuse in
> 	 multiple places.
> 	 Updated to register tegra_i2c_driver from module level rather than subsys
> 	 level.
> 	 Other minor feedback
>  [V9] :  Rebased to 5.0-rc4
> 	 Removed dependency of APB DMA in Kconfig and added conditional check
>  	 in I2C driver to decide on using DMA mode.
> 	 Changed back the allocation of dma buffer during i2c probe.
> 	 Fixed FIFO triggers depending on DMA Vs PIO.
>  [V8] :  Moved back dma init to i2c probe, removed ALL_PACKETS_XFER_COMPLETE
> 	 interrupt and using PACKETS_XFER_COMPLETE interrupt only and some
> 	 other fixes
> 	 Updated Kconfig for APB_DMA dependency
>  [V7] :  Same as V6
>  [V6] :  Updated for proper buffer allocation/freeing, channel release.
> 	 Updated to use exact xfer size for syncing dma buffer.
>  [V5] :  Same as V4
>  [V4] :  Updated to allocate DMA buffer only when DMA mode.
> 	 Updated to fall back to PIO mode when DMA channel request or
> 	 buffer allocation fails.
>  [V3] :  Updated without additional buffer allocation.
>  [V2] :  Updated based on V1 review feedback along with code cleanup for
> 	 proper implementation of DMA.
> 
> 
>  drivers/i2c/busses/i2c-tegra.c | 411 ++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 367 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 118b7023a0f4..fddfb46370e0 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -8,6 +8,8 @@
>  
>  #include <linux/clk.h>
>  #include <linux/delay.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
>  #include <linux/err.h>
>  #include <linux/i2c.h>
>  #include <linux/init.h>
> @@ -44,6 +46,8 @@
>  #define I2C_FIFO_CONTROL_RX_FLUSH		BIT(0)
>  #define I2C_FIFO_CONTROL_TX_TRIG_SHIFT		5
>  #define I2C_FIFO_CONTROL_RX_TRIG_SHIFT		2

I2C_FIFO_CONTROL_TX_TRIG_SHIFT and I2C_FIFO_CONTROL_RX_TRIG_SHIFT are not used anymore in the code, let's remove them.

> +#define I2C_FIFO_CONTROL_TX_TRIG(x)		(((x) - 1) << 5)
> +#define I2C_FIFO_CONTROL_RX_TRIG(x)		(((x) - 1) << 2)
>  #define I2C_FIFO_STATUS				0x060
>  #define I2C_FIFO_STATUS_TX_MASK			0xF0
>  #define I2C_FIFO_STATUS_TX_SHIFT		4
> @@ -125,6 +129,16 @@
>  #define I2C_MST_FIFO_STATUS_TX_MASK		0xff0000
>  #define I2C_MST_FIFO_STATUS_TX_SHIFT		16
>  
> +/* Packet header size in bytes */
> +#define I2C_PACKET_HEADER_SIZE			12
> +
> +/*
> + * Upto I2C_PIO_MODE_MAX_LEN bytes, controller will use PIO mode,
> + * above this, controller will use DMA to fill FIFO.
> + * MAX PIO len is 20 bytes excluding packet header.
> + */
> +#define I2C_PIO_MODE_MAX_LEN			32
> +
>  /*
>   * msg_end_type: The bus control which need to be send at end of transfer.
>   * @MSG_END_STOP: Send stop pulse at end of transfer.
> @@ -166,6 +180,7 @@ enum msg_end_type {
>   *		allowing 0 length transfers.
>   * @supports_bus_clear: Bus Clear support to recover from bus hang during
>   *		SDA stuck low from device for some unknown reasons.
> + * @has_apb_dma: Support of APBDMA on corresponding Tegra chip.
>   */
>  struct tegra_i2c_hw_feature {
>  	bool has_continue_xfer_support;
> @@ -180,6 +195,7 @@ struct tegra_i2c_hw_feature {
>  	bool has_mst_fifo;
>  	const struct i2c_adapter_quirks *quirks;
>  	bool supports_bus_clear;
> +	bool has_apb_dma;
>  };
>  
>  /**
> @@ -191,6 +207,7 @@ struct tegra_i2c_hw_feature {
>   * @fast_clk: clock reference for fast clock of I2C controller
>   * @rst: reset control for the I2C controller
>   * @base: ioremapped registers cookie
> + * @base_phys: Physical base address of the I2C controller
>   * @cont_id: I2C controller ID, used for packet header
>   * @irq: IRQ number of transfer complete interrupt
>   * @irq_disabled: used to track whether or not the interrupt is enabled
> @@ -204,6 +221,13 @@ struct tegra_i2c_hw_feature {
>   * @clk_divisor_non_hs_mode: clock divider for non-high-speed modes
>   * @is_multimaster_mode: track if I2C controller is in multi-master mode
>   * @xfer_lock: lock to serialize transfer submission and processing
> + * @tx_dma_chan: DMA transmit channel
> + * @rx_dma_chan: DMA receive channel
> + * @dma_phys: handle to DMA resources
> + * @dma_buf: pointer to allocated DMA buffer
> + * @dma_buf_size: DMA buffer size
> + * @is_curr_dma_xfer: indicates active DMA transfer
> + * @dma_complete: DMA completion notifier
>   */
>  struct tegra_i2c_dev {
>  	struct device *dev;
> @@ -213,6 +237,7 @@ struct tegra_i2c_dev {
>  	struct clk *fast_clk;
>  	struct reset_control *rst;
>  	void __iomem *base;
> +	phys_addr_t base_phys;
>  	int cont_id;
>  	int irq;
>  	bool irq_disabled;
> @@ -226,6 +251,13 @@ struct tegra_i2c_dev {
>  	u16 clk_divisor_non_hs_mode;
>  	bool is_multimaster_mode;
>  	spinlock_t xfer_lock;
> +	struct dma_chan *tx_dma_chan;
> +	struct dma_chan *rx_dma_chan;
> +	dma_addr_t dma_phys;
> +	u32 *dma_buf;
> +	unsigned int dma_buf_size;
> +	bool is_curr_dma_xfer;
> +	struct completion dma_complete;
>  };
>  
>  static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
> @@ -294,6 +326,109 @@ static void tegra_i2c_unmask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
>  	i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
>  }
>  
> +static void tegra_i2c_dma_complete(void *args)
> +{
> +	struct tegra_i2c_dev *i2c_dev = args;
> +
> +	complete(&i2c_dev->dma_complete);
> +}
> +
> +static int tegra_i2c_dma_submit(struct tegra_i2c_dev *i2c_dev, size_t len)
> +{
> +	struct dma_async_tx_descriptor *dma_desc;
> +	enum dma_transfer_direction dir;
> +	struct dma_chan *chan;
> +
> +	dev_dbg(i2c_dev->dev, "starting DMA for length: %zu\n", len);
> +	reinit_completion(&i2c_dev->dma_complete);
> +	dir = i2c_dev->msg_read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
> +	chan = i2c_dev->msg_read ? i2c_dev->rx_dma_chan : i2c_dev->tx_dma_chan;
> +	dma_desc = dmaengine_prep_slave_single(chan, i2c_dev->dma_phys,
> +					       len, dir, DMA_PREP_INTERRUPT |
> +					       DMA_CTRL_ACK);
> +	if (!dma_desc) {
> +		dev_err(i2c_dev->dev, "failed to get DMA descriptor\n");
> +		return -EINVAL;
> +	}
> +
> +	dma_desc->callback = tegra_i2c_dma_complete;
> +	dma_desc->callback_param = i2c_dev;
> +	dmaengine_submit(dma_desc);
> +	dma_async_issue_pending(chan);
> +	return 0;
> +}
> +
> +static void tegra_i2c_release_dma(struct tegra_i2c_dev *i2c_dev)
> +{
> +	if (i2c_dev->dma_buf) {
> +		dma_free_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> +				  i2c_dev->dma_buf, i2c_dev->dma_phys);
> +		i2c_dev->dma_buf = NULL;
> +	}
> +
> +	if (i2c_dev->tx_dma_chan) {
> +		dma_release_channel(i2c_dev->tx_dma_chan);
> +		i2c_dev->tx_dma_chan = NULL;
> +	}
> +
> +	if (i2c_dev->rx_dma_chan) {
> +		dma_release_channel(i2c_dev->rx_dma_chan);
> +		i2c_dev->rx_dma_chan = NULL;
> +	}
> +}
> +
> +static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
> +{
> +	struct dma_chan *chan;
> +	u32 *dma_buf;
> +	dma_addr_t dma_phys;
> +	int err;
> +
> +	if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA) ||
> +	    !i2c_dev->hw->has_apb_dma) {
> +		err = -ENODEV;
> +		goto err_out;
> +	}
> +
> +	chan = dma_request_slave_channel_reason(i2c_dev->dev, "rx");
> +	if (IS_ERR(chan)) {
> +		err = PTR_ERR(chan);
> +		goto err_out;
> +	}
> +
> +	i2c_dev->rx_dma_chan = chan;
> +
> +	chan = dma_request_slave_channel_reason(i2c_dev->dev, "tx");
> +	if (IS_ERR(chan)) {
> +		err = PTR_ERR(chan);
> +		goto err_out;
> +	}
> +
> +	i2c_dev->tx_dma_chan = chan;
> +
> +	dma_buf = dma_alloc_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
> +				     &dma_phys, GFP_KERNEL | __GFP_NOWARN);
> +	if (!dma_buf) {
> +		dev_err(i2c_dev->dev, "failed to allocate the DMA buffer\n");
> +		err = -ENOMEM;
> +		goto err_out;
> +	}
> +
> +	i2c_dev->dma_buf = dma_buf;
> +	i2c_dev->dma_phys = dma_phys;
> +	return 0;
> +
> +err_out:
> +	tegra_i2c_release_dma(i2c_dev);
> +	if (err != -EPROBE_DEFER) {
> +		dev_err(i2c_dev->dev, "can't use DMA, err: %d, using PIO\n",
> +			err);
> +		return 0;
> +	}
> +
> +	return err;
> +}
> +
>  static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
>  {
>  	unsigned long timeout = jiffies + HZ;
> @@ -571,16 +706,6 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>  		i2c_writel(i2c_dev, 0x00, I2C_SL_ADDR2);
>  	}
>  
> -	if (i2c_dev->hw->has_mst_fifo) {
> -		val = I2C_MST_FIFO_CONTROL_TX_TRIG(8) |
> -		      I2C_MST_FIFO_CONTROL_RX_TRIG(1);
> -		i2c_writel(i2c_dev, val, I2C_MST_FIFO_CONTROL);
> -	} else {
> -		val = 7 << I2C_FIFO_CONTROL_TX_TRIG_SHIFT |
> -			0 << I2C_FIFO_CONTROL_RX_TRIG_SHIFT;
> -		i2c_writel(i2c_dev, val, I2C_FIFO_CONTROL);
> -	}
> -
>  	err = tegra_i2c_flush_fifos(i2c_dev);
>  	if (err)
>  		goto err;
> @@ -660,25 +785,37 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>  	if (i2c_dev->hw->supports_bus_clear && (status & I2C_INT_BUS_CLR_DONE))
>  		goto err;
>  
> -	if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> -		if (i2c_dev->msg_buf_remaining)
> -			tegra_i2c_empty_rx_fifo(i2c_dev);
> -		else
> -			BUG();
> -	}
> +	if (!i2c_dev->is_curr_dma_xfer) {
> +		if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
> +			if (i2c_dev->msg_buf_remaining)
> +				tegra_i2c_empty_rx_fifo(i2c_dev);
> +			else
> +				BUG();
> +		}
>  
> -	if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> -		if (i2c_dev->msg_buf_remaining)
> -			tegra_i2c_fill_tx_fifo(i2c_dev);
> -		else
> -			tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
> +		if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
> +			if (i2c_dev->msg_buf_remaining)
> +				tegra_i2c_fill_tx_fifo(i2c_dev);
> +			else
> +				tegra_i2c_mask_irq(i2c_dev,
> +						   I2C_INT_TX_FIFO_DATA_REQ);
> +		}
>  	}
>  
>  	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
>  	if (i2c_dev->is_dvc)
>  		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>  
> +	/*
> +	 * During message read XFER_COMPLETE interrupt is triggered prior to
> +	 * DMA completion and during message write XFER_COMPLETE interrupt is
> +	 * triggered after DMA completion.
> +	 * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer.
> +	 * so forcing msg_buf_remaining to 0 in DMA mode.
> +	 */
>  	if (status & I2C_INT_PACKET_XFER_COMPLETE) {
> +		if (i2c_dev->is_curr_dma_xfer)
> +			i2c_dev->msg_buf_remaining = 0;
>  		BUG_ON(i2c_dev->msg_buf_remaining);
>  		complete(&i2c_dev->msg_complete);
>  	}
> @@ -694,12 +831,91 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>  	if (i2c_dev->is_dvc)
>  		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
>  
> +	if (i2c_dev->is_curr_dma_xfer) {
> +		if (i2c_dev->msg_read)
> +			dmaengine_terminate_async(i2c_dev->rx_dma_chan);
> +		else
> +			dmaengine_terminate_async(i2c_dev->tx_dma_chan);
> +
> +		complete(&i2c_dev->dma_complete);
> +	}
> +
>  	complete(&i2c_dev->msg_complete);
>  done:
>  	spin_unlock(&i2c_dev->xfer_lock);
>  	return IRQ_HANDLED;
>  }
>  
> +static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
> +				       size_t len)
> +{
> +	u32 val = 0, reg;
> +	u8 dma_burst = 0;
> +	struct dma_slave_config slv_config = {0};
> +	struct dma_chan *chan;
> +	int ret;
> +	unsigned long reg_offset;
> +
> +	if (i2c_dev->hw->has_mst_fifo)
> +		reg = I2C_MST_FIFO_CONTROL;
> +	else
> +		reg = I2C_FIFO_CONTROL;
> +
> +	if (i2c_dev->is_curr_dma_xfer) {
> +		if (len & 0xF)
> +			dma_burst = 1;
> +		else if (len & 0x10)
> +			dma_burst = 4;
> +		else
> +			dma_burst = 8;
> +
> +		if (i2c_dev->msg_read) {
> +			chan = i2c_dev->rx_dma_chan;
> +			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_RX_FIFO);
> +			slv_config.src_addr = i2c_dev->base_phys + reg_offset;
> +			slv_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +			slv_config.src_maxburst = dma_burst;
> +
> +			if (i2c_dev->hw->has_mst_fifo)
> +				val |= I2C_MST_FIFO_CONTROL_RX_TRIG(dma_burst);
> +			else
> +				val |= I2C_FIFO_CONTROL_RX_TRIG(dma_burst);
> +		} else {
> +			chan = i2c_dev->tx_dma_chan;
> +			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_TX_FIFO);
> +			slv_config.dst_addr = i2c_dev->base_phys + reg_offset;
> +			slv_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +			slv_config.dst_maxburst = dma_burst;
> +
> +			if (i2c_dev->hw->has_mst_fifo)
> +				val |= I2C_MST_FIFO_CONTROL_TX_TRIG(dma_burst);
> +			else
> +				val |= I2C_FIFO_CONTROL_TX_TRIG(dma_burst);
> +		}
> +
> +		slv_config.device_fc = true;
> +		ret = dmaengine_slave_config(chan, &slv_config);
> +		if (ret < 0) {
> +			dev_err(i2c_dev->dev, "DMA slave config failed: %d\n",
> +				ret);
> +			dev_err(i2c_dev->dev, "fallbacking to PIO\n");
> +			tegra_i2c_release_dma(i2c_dev);
> +			i2c_dev->is_curr_dma_xfer = false;
> +		} else {
> +			goto out;
> +		}
> +	}
> +
> +	if (i2c_dev->hw->has_mst_fifo)
> +		val = I2C_MST_FIFO_CONTROL_TX_TRIG(8) |
> +		      I2C_MST_FIFO_CONTROL_RX_TRIG(1);
> +	else
> +		val = I2C_FIFO_CONTROL_TX_TRIG(8) |
> +		      I2C_FIFO_CONTROL_RX_TRIG(1);
> +out:
> +	i2c_writel(i2c_dev, val, reg);
> +}
> +
>  static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev)
>  {
>  	int err;
> @@ -744,6 +960,10 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  	u32 int_mask;
>  	unsigned long time_left;
>  	unsigned long flags;
> +	size_t xfer_size;
> +	u32 *buffer = NULL;
> +	int err = 0;
> +	bool dma;
>  
>  	tegra_i2c_flush_fifos(i2c_dev);
>  
> @@ -753,19 +973,58 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  	i2c_dev->msg_read = (msg->flags & I2C_M_RD);
>  	reinit_completion(&i2c_dev->msg_complete);
>  
> +	if (i2c_dev->msg_read)
> +		xfer_size = msg->len;
> +	else
> +		xfer_size = msg->len + I2C_PACKET_HEADER_SIZE;
> +
> +	xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD);
> +	i2c_dev->is_curr_dma_xfer = (xfer_size > I2C_PIO_MODE_MAX_LEN) &&
> +				    i2c_dev->dma_buf;
> +	tegra_i2c_config_fifo_trig(i2c_dev, xfer_size);
> +	dma = i2c_dev->is_curr_dma_xfer;
> +
>  	spin_lock_irqsave(&i2c_dev->xfer_lock, flags);
>  
>  	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
>  	tegra_i2c_unmask_irq(i2c_dev, int_mask);
> +	if (dma) {
> +		if (i2c_dev->msg_read) {
> +			dma_sync_single_for_device(i2c_dev->dev,
> +						   i2c_dev->dma_phys,
> +						   xfer_size,
> +						   DMA_FROM_DEVICE);
> +			err = tegra_i2c_dma_submit(i2c_dev, xfer_size);
> +			if (err < 0) {
> +				dev_err(i2c_dev->dev,
> +					"starting RX DMA failed, err %d\n",
> +					err);
> +				goto unlock;
> +			}
> +
> +		} else {
> +			dma_sync_single_for_cpu(i2c_dev->dev,
> +						i2c_dev->dma_phys,
> +						xfer_size,
> +						DMA_TO_DEVICE);
> +			buffer = i2c_dev->dma_buf;
> +		}
> +	}
>  
>  	packet_header = (0 << PACKET_HEADER0_HEADER_SIZE_SHIFT) |
>  			PACKET_HEADER0_PROTOCOL_I2C |
>  			(i2c_dev->cont_id << PACKET_HEADER0_CONT_ID_SHIFT) |
>  			(1 << PACKET_HEADER0_PACKET_ID_SHIFT);
> -	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> +	if (dma && !i2c_dev->msg_read)
> +		*buffer++ = packet_header;
> +	else
> +		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
>  
>  	packet_header = msg->len - 1;
> -	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> +	if (dma && !i2c_dev->msg_read)
> +		*buffer++ = packet_header;
> +	else
> +		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
>  
>  	packet_header = I2C_HEADER_IE_ENABLE;
>  	if (end_state == MSG_END_CONTINUE)
> @@ -782,23 +1041,81 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
>  		packet_header |= I2C_HEADER_CONT_ON_NAK;
>  	if (msg->flags & I2C_M_RD)
>  		packet_header |= I2C_HEADER_READ;
> -	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> -
> -	if (!(msg->flags & I2C_M_RD))
> -		tegra_i2c_fill_tx_fifo(i2c_dev);
> +	if (dma && !i2c_dev->msg_read)
> +		*buffer++ = packet_header;
> +	else
> +		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
> +
> +	if (!i2c_dev->msg_read) {
> +		if (dma) {
> +			memcpy(buffer, msg->buf, msg->len);

It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.

[snip]
Dmitry Osipenko Feb. 7, 2019, 2:52 p.m. | #3
06.02.2019 22:16, Sowjanya Komatineni пишет:
> This patch adds DMA support for Tegra I2C.
> 
> Tegra I2C TX and RX FIFO depth is 8 words. PIO mode is used for
> transfer size of the max FIFO depth and DMA mode is used for
> transfer size higher than max FIFO depth to save CPU overhead.
> 
> PIO mode needs full intervention of CPU to fill or empty FIFO's
> and also need to service multiple data requests interrupt for the
> same transaction. This adds delay between data bytes of the same
> transfer when CPU is fully loaded and some slave devices has
> internal timeout for no bus activity and stops transaction to
> avoid bus hang. DMA mode is helpful in such cases.
> 
> DMA mode is also helpful for Large transfers during downloading or
> uploading FW over I2C to some external devices.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
> ---


[snip]

> @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	ret = tegra_i2c_init_dma(i2c_dev);
> +	if (ret < 0)
> +		goto disable_div_clk;
> +
>  	ret = tegra_i2c_init(i2c_dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");


Missing DMA resourcing release on probe failure.


diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 7921d3e6237d..11f25357b843 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1612,14 +1612,14 @@ static int tegra_i2c_probe(struct platform_device *pdev)
        ret = tegra_i2c_init(i2c_dev, false);
        if (ret) {
                dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
-               goto disable_div_clk;
+               goto release_dma;
        }
 
        ret = devm_request_irq(&pdev->dev, i2c_dev->irq,
                        tegra_i2c_isr, 0, dev_name(&pdev->dev), i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq %i\n", i2c_dev->irq);
-               goto disable_div_clk;
+               goto release_dma;
        }
 
        i2c_set_adapdata(&i2c_dev->adapter, i2c_dev);
@@ -1633,10 +1633,13 @@ static int tegra_i2c_probe(struct platform_device *pdev)
 
        ret = i2c_add_numbered_adapter(&i2c_dev->adapter);
        if (ret)
-               goto disable_div_clk;
+               goto release_dma;
 
        return 0;
 
+release_dma:
+       tegra_i2c_release_dma(i2c_dev);
+
 disable_div_clk:
        if (i2c_dev->is_multimaster_mode)
                clk_disable(i2c_dev->div_clk);
Sowjanya Komatineni Feb. 7, 2019, 3:11 p.m. | #4
> 
> 
> > @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> >  		}
> >  	}
> >  
> > +	ret = tegra_i2c_init_dma(i2c_dev);
> > +	if (ret < 0)
> > +		goto disable_div_clk;
> > +
> >  	ret = tegra_i2c_init(i2c_dev);
> >  	if (ret) {
> >  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
>
>
> Missing DMA resourcing release on probe failure.

If probe fails due to other reasons, then I2C interface will not be available and boot will not even happen.
Do we need DMA resourcing release?
Dmitry Osipenko Feb. 7, 2019, 3:17 p.m. | #5
07.02.2019 18:11, Sowjanya Komatineni пишет:
>>
>>
>>> @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>>>  		}
>>>  	}
>>>  
>>> +	ret = tegra_i2c_init_dma(i2c_dev);
>>> +	if (ret < 0)
>>> +		goto disable_div_clk;
>>> +
>>>  	ret = tegra_i2c_init(i2c_dev);
>>>  	if (ret) {
>>>  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
>>
>>
>> Missing DMA resourcing release on probe failure.
> 
> If probe fails due to other reasons, then I2C interface will not be available and boot will not even happen.
> Do we need DMA resourcing release?
> 

Absolutely! Every allocated resource must be released.
Sowjanya Komatineni Feb. 7, 2019, 3:17 p.m. | #6
> > 
> > > @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> > >  		}
> > >  	}
> > >  
> > > +	ret = tegra_i2c_init_dma(i2c_dev);
> > > +	if (ret < 0)
> > > +		goto disable_div_clk;
> > > +
> > >  	ret = tegra_i2c_init(i2c_dev);
> > >  	if (ret) {
> > >  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
> >
> >
> > Missing DMA resourcing release on probe failure.
>
If probe fails due to other reasons, then I2C interface will not be available and boot will not even happen.
Do we need DMA resourcing release?
Probe can fail due to timeout or from pm_runtime.. and if i2c fails lots of things don’t happen properly and doesn’t boot.

Will add but want to check..
Sowjanya Komatineni Feb. 7, 2019, 3:23 p.m. | #7
>It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.

Yes, This is known to me and I will add separate patch for this to update quirks to take care for t186 and t194 to exclude packet hdr lengths
There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
Need to update quirk to exclude packet header
Dmitry Osipenko Feb. 7, 2019, 3:56 p.m. | #8
07.02.2019 18:17, Sowjanya Komatineni пишет:
>>>
>>>> @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>>>>  		}
>>>>  	}
>>>>  
>>>> +	ret = tegra_i2c_init_dma(i2c_dev);
>>>> +	if (ret < 0)
>>>> +		goto disable_div_clk;
>>>> +
>>>>  	ret = tegra_i2c_init(i2c_dev);
>>>>  	if (ret) {
>>>>  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
>>>
>>>
>>> Missing DMA resourcing release on probe failure.
>>
> If probe fails due to other reasons, then I2C interface will not be available and boot will not even happen.
> Do we need DMA resourcing release?
> Probe can fail due to timeout or from pm_runtime.. and if i2c fails lots of things don’t happen properly and doesn’t boot.
> 
> Will add but want to check..
> 

1) There is no guarantee that other error cases won't return -EPROBE_DEFER.

2) I2C driver could be compiled as a module.

3) It is simply a bad programming practice to leak resources.
Dmitry Osipenko Feb. 7, 2019, 4:01 p.m. | #9
07.02.2019 18:23, Sowjanya Komatineni пишет:
> 
>> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
> 
> Yes, This is known to me and I will add separate patch for this to update quirks to take care for t186 and t194 to exclude packet hdr lengths
> There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
> Need to update quirk to exclude packet header
> 

No. This is a bug of this patch, it must be fixed in this patch as well. 

Please include this snippet into the next version of this patch.

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 7921d3e6237d..0ed8162a37e4 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1293,7 +1293,7 @@ static const struct i2c_algorithm tegra_i2c_algo = {
 static const struct i2c_adapter_quirks tegra_i2c_quirks = {
        .flags = I2C_AQ_NO_ZERO_LEN,
        .max_read_len = 4096,
-       .max_write_len = 4096,
+       .max_write_len = 4096 - I2C_PACKET_HEADER_SIZE,
 };
 
 static const struct i2c_adapter_quirks tegra194_i2c_quirks = {
@@ -1545,7 +1545,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
        i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node,
                                                  "nvidia,tegra20-i2c-dvc");
        i2c_dev->adapter.quirks = i2c_dev->hw->quirks;
-       i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_write_len;
+       i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_read_len;
        init_completion(&i2c_dev->msg_complete);
        init_completion(&i2c_dev->dma_complete);
        spin_lock_init(&i2c_dev->xfer_lock);
Thierry Reding Feb. 7, 2019, 4:02 p.m. | #10
On Thu, Feb 07, 2019 at 03:11:06PM +0000, Sowjanya Komatineni wrote:
> > 
> > 
> > > @@ -1124,6 +1453,10 @@ static int tegra_i2c_probe(struct platform_device *pdev)
> > >  		}
> > >  	}
> > >  
> > > +	ret = tegra_i2c_init_dma(i2c_dev);
> > > +	if (ret < 0)
> > > +		goto disable_div_clk;
> > > +
> > >  	ret = tegra_i2c_init(i2c_dev);
> > >  	if (ret) {
> > >  		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
> >
> >
> > Missing DMA resourcing release on probe failure.
> 
> If probe fails due to other reasons, then I2C interface will not be
> available and boot will not even happen.
> Do we need DMA resourcing release?

It's also possible that probe will fail for one of the I2C controllers
that is not critical to basic system functionality. You don't want to
leak these resources because it's bad practice (other people reading the
code may conclude that it's okay to leak resources).

Also, if everyone is really careful about not leaking resources, it
makes it much easier to track down leaks.

Thierry
Thierry Reding Feb. 7, 2019, 4:06 p.m. | #11
On Thu, Feb 07, 2019 at 07:01:45PM +0300, Dmitry Osipenko wrote:
> 07.02.2019 18:23, Sowjanya Komatineni пишет:
> > 
> >> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
> > 
> > Yes, This is known to me and I will add separate patch for this to update quirks to take care for t186 and t194 to exclude packet hdr lengths
> > There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
> > Need to update quirk to exclude packet header
> > 
> 
> No. This is a bug of this patch, it must be fixed in this patch as well. 
> 
> Please include this snippet into the next version of this patch.
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 7921d3e6237d..0ed8162a37e4 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1293,7 +1293,7 @@ static const struct i2c_algorithm tegra_i2c_algo = {
>  static const struct i2c_adapter_quirks tegra_i2c_quirks = {
>         .flags = I2C_AQ_NO_ZERO_LEN,
>         .max_read_len = 4096,
> -       .max_write_len = 4096,
> +       .max_write_len = 4096 - I2C_PACKET_HEADER_SIZE,
>  };
>  
>  static const struct i2c_adapter_quirks tegra194_i2c_quirks = {
> @@ -1545,7 +1545,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>         i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node,
>                                                   "nvidia,tegra20-i2c-dvc");
>         i2c_dev->adapter.quirks = i2c_dev->hw->quirks;
> -       i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_write_len;
> +       i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_read_len;
>         init_completion(&i2c_dev->msg_complete);
>         init_completion(&i2c_dev->dma_complete);
>         spin_lock_init(&i2c_dev->xfer_lock);

I'm not sure we actually need this. My understanding is that it's really
the payload size that's 4 KiB and 64 KiB, respectively. I don't think
that includes the header.

Thierry
Sowjanya Komatineni Feb. 7, 2019, 4:08 p.m. | #12
> > >> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
> > > 
> > > Yes, This is known to me and I will add separate patch for this to 
> > > update quirks to take care for t186 and t194 to exclude packet hdr lengths There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
> > > Need to update quirk to exclude packet header
> > > 
> > 
> > No. This is a bug of this patch, it must be fixed in this patch as well. 
> > 
>
>
> I'm not sure we actually need this. My understanding is that it's really the payload size that's 4 KiB and 64 KiB, respectively. I don't think that includes the header.
>
> Thierry

As per the design, Yes that’s including the HEADER. Its total transfer per packet including header.
Dmitry Osipenko Feb. 7, 2019, 4:17 p.m. | #13
07.02.2019 19:08, Sowjanya Komatineni пишет:
> 
>>>>> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
>>>>
>>>> Yes, This is known to me and I will add separate patch for this to 
>>>> update quirks to take care for t186 and t194 to exclude packet hdr lengths There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
>>>> Need to update quirk to exclude packet header
>>>>
>>>
>>> No. This is a bug of this patch, it must be fixed in this patch as well. 
>>>
>>
>>
>> I'm not sure we actually need this. My understanding is that it's really the payload size that's 4 KiB and 64 KiB, respectively. I don't think that includes the header.
>>
>> Thierry
> 
> As per the design, Yes that’s including the HEADER. Its total transfer per packet including header.
> 

My understanding that I2C's max read/write sizes quirks are the payload limits, and so excluding the header size. Hence I'm not sure what you are trying to say, Thierry.

Sowjanya, also.. it should be fine if you'll include the separate patch into this series, placing it before this DMA-patch. I just read your message as "patch separately from this series".
Sowjanya Komatineni Feb. 7, 2019, 6:02 p.m. | #14
> >>>>> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
> >>>>
> >>>> Yes, This is known to me and I will add separate patch for this to 
> >>>> update quirks to take care for t186 and t194 to exclude packet hdr lengths There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
> >>>> Need to update quirk to exclude packet header
> >>>>
> >>>
> >>> No. This is a bug of this patch, it must be fixed in this patch as well. 
> >>>
> >>
> >>
> >> I'm not sure we actually need this. My understanding is that it's really the payload size that's 4 KiB and 64 KiB, respectively. I don't think that includes the header.
> >>
> >> Thierry
> > 
> > As per the design, Yes that’s including the HEADER. Its total transfer per packet including header.
> > 
>
> My understanding that I2C's max read/write sizes quirks are the payload limits, and so excluding the header size. Hence I'm not sure what you are trying to say, Thierry.
>
> Sowjanya, also.. it should be fine if you'll include the separate patch into this series, placing it before this DMA-patch. I just read your message as "patch separately from this series".

OK, Will add that prior to DMA patch. V15 will include max transfer limit update, dma resource releases on probe faiures, and other minor errors in V14 feedback.
Will wait for any more feedbacks before releasing V15...
Dmitry Osipenko Feb. 7, 2019, 6:22 p.m. | #15
07.02.2019 21:02, Sowjanya Komatineni пишет:
> 
>>>>>>> It became apparent to me that there is a problem here. The size of dma_buf is 4096 bytes and maximum message length is 4096 too, we have pushed 12 bytes packet_header to the buffer >and now there are 4084 bytes left for the message in the buffer. Hence transfer of 4KB will cause buffer overflow and either crash kernel or corrupt memory. One solution is to just always >push packet_header using PIO, other to reduce max_write_len or increase dma_buf size.
>>>>>>
>>>>>> Yes, This is known to me and I will add separate patch for this to 
>>>>>> update quirks to take care for t186 and t194 to exclude packet hdr lengths There was separate patch when quirks were added and it got merged already from 5.0-rc1 but don’t want to sneak that here. Will send separate patch to take care of this.
>>>>>> Need to update quirk to exclude packet header
>>>>>>
>>>>>
>>>>> No. This is a bug of this patch, it must be fixed in this patch as well. 
>>>>>
>>>>
>>>>
>>>> I'm not sure we actually need this. My understanding is that it's really the payload size that's 4 KiB and 64 KiB, respectively. I don't think that includes the header.
>>>>
>>>> Thierry
>>>
>>> As per the design, Yes that’s including the HEADER. Its total transfer per packet including header.
>>>
>>
>> My understanding that I2C's max read/write sizes quirks are the payload limits, and so excluding the header size. Hence I'm not sure what you are trying to say, Thierry.
>>
>> Sowjanya, also.. it should be fine if you'll include the separate patch into this series, placing it before this DMA-patch. I just read your message as "patch separately from this series".
> 
> OK, Will add that prior to DMA patch. V15 will include max transfer limit update, dma resource releases on probe faiures, and other minor errors in V14 feedback.
> Will wait for any more feedbacks before releasing V15...
> 

Thanks, I'll add couple more minor comments then.
Dmitry Osipenko Feb. 7, 2019, 6:24 p.m. | #16
06.02.2019 22:16, Sowjanya Komatineni пишет:

> +		if (i2c_dev->msg_read && i2c_dev->msg_err == I2C_ERR_NONE) {
> +			dma_sync_single_for_cpu(i2c_dev->dev,
> +						i2c_dev->dma_phys,
> +						xfer_size,
> +						DMA_FROM_DEVICE);
> +			memcpy(i2c_dev->msg_buf, i2c_dev->dma_buf,
> +			       msg->len);
> +		}
> +
> +		if (i2c_dev->msg_err != I2C_ERR_NONE) {
> +			dmaengine_synchronize(i2c_dev->msg_read ?
> +					      i2c_dev->rx_dma_chan :
> +					      i2c_dev->tx_dma_chan);
> +		}

Minor nit: parentheses are not really around the dmaengine_synchronize()
Dmitry Osipenko Feb. 7, 2019, 6:50 p.m. | #17
06.02.2019 22:16, Sowjanya Komatineni пишет:
> @@ -920,6 +1238,7 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>  	.has_mst_fifo = false,
>  	.quirks = &tegra_i2c_quirks,
>  	.supports_bus_clear = false,
> +	.has_apb_dma = true,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -935,6 +1254,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>  	.has_mst_fifo = false,
>  	.quirks = &tegra_i2c_quirks,
>  	.supports_bus_clear = false,
> +	.has_apb_dma = true,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
> @@ -950,6 +1270,7 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
>  	.has_mst_fifo = false,
>  	.quirks = &tegra_i2c_quirks,
>  	.supports_bus_clear = true,
> +	.has_apb_dma = true,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
> @@ -965,6 +1286,7 @@ static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
>  	.has_mst_fifo = false,
>  	.quirks = &tegra_i2c_quirks,
>  	.supports_bus_clear = true,
> +	.has_apb_dma = true,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> @@ -980,6 +1302,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
>  	.has_mst_fifo = false,
>  	.quirks = &tegra_i2c_quirks,
>  	.supports_bus_clear = true,
> +	.has_apb_dma = true,
>  };

T186 is missed here.

>  
>  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> @@ -995,6 +1318,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
>  	.has_mst_fifo = true,
>  	.quirks = &tegra194_i2c_quirks,
>  	.supports_bus_clear = true,
> +	.has_apb_dma = false,
>  };
Dmitry Osipenko Feb. 7, 2019, 6:55 p.m. | #18
06.02.2019 22:16, Sowjanya Komatineni пишет:
>  /**
> @@ -191,6 +207,7 @@ struct tegra_i2c_hw_feature {
>   * @fast_clk: clock reference for fast clock of I2C controller
>   * @rst: reset control for the I2C controller
>   * @base: ioremapped registers cookie
> + * @base_phys: Physical base address of the I2C controller

Minor nit: "physical" with lower case for consistency, please
Sowjanya Komatineni Feb. 7, 2019, 6:56 p.m. | #19
> >  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = { @@ 
> > -980,6 +1302,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> >  	.has_mst_fifo = false,
> >  	.quirks = &tegra_i2c_quirks,
> >  	.supports_bus_clear = true,
> > +	.has_apb_dma = true,
> >  };
>
> T186 is missed here.

Currently t186 hw feature is not present in existing linux next and device trees use both t186 and t114 compatibles, so t114 is being applies.
But dmas are not used for t186 yet.

T186 hw feature is added for first time as part of interface timing and its in patch next to this patch in same series.
This is the same from beginning of all these series.

>
> >  
> >  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = { @@ 
> > -995,6 +1318,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> >  	.has_mst_fifo = true,
> >  	.quirks = &tegra194_i2c_quirks,
> >  	.supports_bus_clear = true,
> > +	.has_apb_dma = false,
> >  };
Dmitry Osipenko Feb. 7, 2019, 7:03 p.m. | #20
07.02.2019 21:56, Sowjanya Komatineni пишет:
>  
>>>  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = { @@ 
>>> -980,6 +1302,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
>>>  	.has_mst_fifo = false,
>>>  	.quirks = &tegra_i2c_quirks,
>>>  	.supports_bus_clear = true,
>>> +	.has_apb_dma = true,
>>>  };
>>
>> T186 is missed here.
> 
> Currently t186 hw feature is not present in existing linux next and device trees use both t186 and t114 compatibles, so t114 is being applies.
> But dmas are not used for t186 yet.
> 
> T186 hw feature is added for first time as part of interface timing and its in patch next to this patch in same series.
> This is the same from beginning of all these series.
> 
>>
>>>  
>>>  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = { @@ 
>>> -995,6 +1318,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
>>>  	.has_mst_fifo = true,
>>>  	.quirks = &tegra194_i2c_quirks,
>>>  	.supports_bus_clear = true,
>>> +	.has_apb_dma = false,
>>>  };
> 

You added "has_apb_dma" for T194 and not T186 in this patch, I happened to notice it only right now. Please, let's be consistent and set the new field for all of the platforms in this patch.
Dmitry Osipenko Feb. 7, 2019, 7:14 p.m. | #21
06.02.2019 22:16, Sowjanya Komatineni пишет:
> +static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
> +				       size_t len)
> +{
> +	u32 val = 0, reg;
> +	u8 dma_burst = 0;
> +	struct dma_slave_config slv_config = {0};
> +	struct dma_chan *chan;
> +	int ret;
> +	unsigned long reg_offset;
> +
> +	if (i2c_dev->hw->has_mst_fifo)
> +		reg = I2C_MST_FIFO_CONTROL;
> +	else
> +		reg = I2C_FIFO_CONTROL;
> +
> +	if (i2c_dev->is_curr_dma_xfer) {
> +		if (len & 0xF)
> +			dma_burst = 1;
> +		else if (len & 0x10)
> +			dma_burst = 4;
> +		else
> +			dma_burst = 8;
> +
> +		if (i2c_dev->msg_read) {
> +			chan = i2c_dev->rx_dma_chan;
> +			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_RX_FIFO);
> +			slv_config.src_addr = i2c_dev->base_phys + reg_offset;
> +			slv_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +			slv_config.src_maxburst = dma_burst;
> +
> +			if (i2c_dev->hw->has_mst_fifo)
> +				val |= I2C_MST_FIFO_CONTROL_RX_TRIG(dma_burst);
> +			else
> +				val |= I2C_FIFO_CONTROL_RX_TRIG(dma_burst);
> +		} else {
> +			chan = i2c_dev->tx_dma_chan;
> +			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_TX_FIFO);
> +			slv_config.dst_addr = i2c_dev->base_phys + reg_offset;
> +			slv_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +			slv_config.dst_maxburst = dma_burst;
> +
> +			if (i2c_dev->hw->has_mst_fifo)
> +				val |= I2C_MST_FIFO_CONTROL_TX_TRIG(dma_burst);
> +			else
> +				val |= I2C_FIFO_CONTROL_TX_TRIG(dma_burst);
> +		}

Minor nit: let's replace "|=" with "=" for consistency, and then "u32 val = 0," to just "u32 val,".

> +
> +		slv_config.device_fc = true;
> +		ret = dmaengine_slave_config(chan, &slv_config);
> +		if (ret < 0) {
> +			dev_err(i2c_dev->dev, "DMA slave config failed: %d\n",
> +				ret);
> +			dev_err(i2c_dev->dev, "fallbacking to PIO\n");
> +			tegra_i2c_release_dma(i2c_dev);
> +			i2c_dev->is_curr_dma_xfer = false;
> +		} else {
> +			goto out;
> +		}
> +	}
> +
> +	if (i2c_dev->hw->has_mst_fifo)
> +		val = I2C_MST_FIFO_CONTROL_TX_TRIG(8) |
> +		      I2C_MST_FIFO_CONTROL_RX_TRIG(1);
> +	else
> +		val = I2C_FIFO_CONTROL_TX_TRIG(8) |
> +		      I2C_FIFO_CONTROL_RX_TRIG(1);
> +out:
> +	i2c_writel(i2c_dev, val, reg);
> +}
Sowjanya Komatineni Feb. 7, 2019, 7:14 p.m. | #22
> >>>  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = { @@ 
> >>> -980,6 +1302,7 @@ static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> >>>  	.has_mst_fifo = false,
> >>>  	.quirks = &tegra_i2c_quirks,
> >>>  	.supports_bus_clear = true,
> >>> +	.has_apb_dma = true,
> >>>  };
> >>
> >> T186 is missed here.
> > 
> > Currently t186 hw feature is not present in existing linux next and device trees use both t186 and t114 compatibles, so t114 is being applies.
> > But dmas are not used for t186 yet.
> > 
> > T186 hw feature is added for first time as part of interface timing and its in patch next to this patch in same series.
> > This is the same from beginning of all these series.
> >
> >>
> >>>  
> >>>  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = { @@ 
> >>> -995,6 +1318,7 @@ static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
> >>>  	.has_mst_fifo = true,
> >>>  	.quirks = &tegra194_i2c_quirks,
> >>>  	.supports_bus_clear = true,
> >>> +	.has_apb_dma = false,
> >>>  };
> > 
>
> You added "has_apb_dma" for T194 and not T186 in this patch, I happened to notice it only right now. Please, let's be consistent and set the new field for all of the platforms in this patch.

OK, Will move t186 hw feature addition to this path from interface timing to reflect apb dma flag.
Dmitry Osipenko Feb. 7, 2019, 8:22 p.m. | #23
07.02.2019 22:14, Dmitry Osipenko пишет:
> 06.02.2019 22:16, Sowjanya Komatineni пишет:
>> +static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
>> +				       size_t len)
>> +{
>> +	u32 val = 0, reg;
>> +	u8 dma_burst = 0;

There is no need to set dma_burst to zero as well. In general you only need to initialize variables if code uses the uninitialized variable.

>> +	struct dma_slave_config slv_config = {0};
>> +	struct dma_chan *chan;
>> +	int ret;
>> +	unsigned long reg_offset;
>> +
>> +	if (i2c_dev->hw->has_mst_fifo)
>> +		reg = I2C_MST_FIFO_CONTROL;
>> +	else
>> +		reg = I2C_FIFO_CONTROL;
>> +
>> +	if (i2c_dev->is_curr_dma_xfer) {
>> +		if (len & 0xF)
>> +			dma_burst = 1;
>> +		else if (len & 0x10)
>> +			dma_burst = 4;
>> +		else
>> +			dma_burst = 8;

In this case compiler just ignores the first initialization because it is explicitly initialized later on in the code path that actually uses the dma_burst variable. Avoiding unnecessary initialization helps to keep code a bit more clean.
Dmitry Osipenko Feb. 7, 2019, 8:46 p.m. | #24
06.02.2019 22:16, Sowjanya Komatineni пишет:
> +	if (!i2c_dev->msg_read) {
> +		if (dma) {
> +			memcpy(buffer, msg->buf, msg->len);
> +			dma_sync_single_for_device(i2c_dev->dev,
> +						   i2c_dev->dma_phys,
> +						   xfer_size,
> +						   DMA_TO_DEVICE);
> +			err = tegra_i2c_dma_submit(i2c_dev, xfer_size);
> +			if (err < 0) {
> +				dev_err(i2c_dev->dev,
> +					"starting TX DMA failed, err %d\n",
> +					err);
> +				goto unlock;
> +			}
> +

This newline is not really needed here.

> +		} else {
> +			tegra_i2c_fill_tx_fifo(i2c_dev);
> +		}
> +	}

That's my last comment for v14. Looking forward for v15!

Patch

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 118b7023a0f4..fddfb46370e0 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -8,6 +8,8 @@ 
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
@@ -44,6 +46,8 @@ 
 #define I2C_FIFO_CONTROL_RX_FLUSH		BIT(0)
 #define I2C_FIFO_CONTROL_TX_TRIG_SHIFT		5
 #define I2C_FIFO_CONTROL_RX_TRIG_SHIFT		2
+#define I2C_FIFO_CONTROL_TX_TRIG(x)		(((x) - 1) << 5)
+#define I2C_FIFO_CONTROL_RX_TRIG(x)		(((x) - 1) << 2)
 #define I2C_FIFO_STATUS				0x060
 #define I2C_FIFO_STATUS_TX_MASK			0xF0
 #define I2C_FIFO_STATUS_TX_SHIFT		4
@@ -125,6 +129,16 @@ 
 #define I2C_MST_FIFO_STATUS_TX_MASK		0xff0000
 #define I2C_MST_FIFO_STATUS_TX_SHIFT		16
 
+/* Packet header size in bytes */
+#define I2C_PACKET_HEADER_SIZE			12
+
+/*
+ * Upto I2C_PIO_MODE_MAX_LEN bytes, controller will use PIO mode,
+ * above this, controller will use DMA to fill FIFO.
+ * MAX PIO len is 20 bytes excluding packet header.
+ */
+#define I2C_PIO_MODE_MAX_LEN			32
+
 /*
  * msg_end_type: The bus control which need to be send at end of transfer.
  * @MSG_END_STOP: Send stop pulse at end of transfer.
@@ -166,6 +180,7 @@  enum msg_end_type {
  *		allowing 0 length transfers.
  * @supports_bus_clear: Bus Clear support to recover from bus hang during
  *		SDA stuck low from device for some unknown reasons.
+ * @has_apb_dma: Support of APBDMA on corresponding Tegra chip.
  */
 struct tegra_i2c_hw_feature {
 	bool has_continue_xfer_support;
@@ -180,6 +195,7 @@  struct tegra_i2c_hw_feature {
 	bool has_mst_fifo;
 	const struct i2c_adapter_quirks *quirks;
 	bool supports_bus_clear;
+	bool has_apb_dma;
 };
 
 /**
@@ -191,6 +207,7 @@  struct tegra_i2c_hw_feature {
  * @fast_clk: clock reference for fast clock of I2C controller
  * @rst: reset control for the I2C controller
  * @base: ioremapped registers cookie
+ * @base_phys: Physical base address of the I2C controller
  * @cont_id: I2C controller ID, used for packet header
  * @irq: IRQ number of transfer complete interrupt
  * @irq_disabled: used to track whether or not the interrupt is enabled
@@ -204,6 +221,13 @@  struct tegra_i2c_hw_feature {
  * @clk_divisor_non_hs_mode: clock divider for non-high-speed modes
  * @is_multimaster_mode: track if I2C controller is in multi-master mode
  * @xfer_lock: lock to serialize transfer submission and processing
+ * @tx_dma_chan: DMA transmit channel
+ * @rx_dma_chan: DMA receive channel
+ * @dma_phys: handle to DMA resources
+ * @dma_buf: pointer to allocated DMA buffer
+ * @dma_buf_size: DMA buffer size
+ * @is_curr_dma_xfer: indicates active DMA transfer
+ * @dma_complete: DMA completion notifier
  */
 struct tegra_i2c_dev {
 	struct device *dev;
@@ -213,6 +237,7 @@  struct tegra_i2c_dev {
 	struct clk *fast_clk;
 	struct reset_control *rst;
 	void __iomem *base;
+	phys_addr_t base_phys;
 	int cont_id;
 	int irq;
 	bool irq_disabled;
@@ -226,6 +251,13 @@  struct tegra_i2c_dev {
 	u16 clk_divisor_non_hs_mode;
 	bool is_multimaster_mode;
 	spinlock_t xfer_lock;
+	struct dma_chan *tx_dma_chan;
+	struct dma_chan *rx_dma_chan;
+	dma_addr_t dma_phys;
+	u32 *dma_buf;
+	unsigned int dma_buf_size;
+	bool is_curr_dma_xfer;
+	struct completion dma_complete;
 };
 
 static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
@@ -294,6 +326,109 @@  static void tegra_i2c_unmask_irq(struct tegra_i2c_dev *i2c_dev, u32 mask)
 	i2c_writel(i2c_dev, int_mask, I2C_INT_MASK);
 }
 
+static void tegra_i2c_dma_complete(void *args)
+{
+	struct tegra_i2c_dev *i2c_dev = args;
+
+	complete(&i2c_dev->dma_complete);
+}
+
+static int tegra_i2c_dma_submit(struct tegra_i2c_dev *i2c_dev, size_t len)
+{
+	struct dma_async_tx_descriptor *dma_desc;
+	enum dma_transfer_direction dir;
+	struct dma_chan *chan;
+
+	dev_dbg(i2c_dev->dev, "starting DMA for length: %zu\n", len);
+	reinit_completion(&i2c_dev->dma_complete);
+	dir = i2c_dev->msg_read ? DMA_DEV_TO_MEM : DMA_MEM_TO_DEV;
+	chan = i2c_dev->msg_read ? i2c_dev->rx_dma_chan : i2c_dev->tx_dma_chan;
+	dma_desc = dmaengine_prep_slave_single(chan, i2c_dev->dma_phys,
+					       len, dir, DMA_PREP_INTERRUPT |
+					       DMA_CTRL_ACK);
+	if (!dma_desc) {
+		dev_err(i2c_dev->dev, "failed to get DMA descriptor\n");
+		return -EINVAL;
+	}
+
+	dma_desc->callback = tegra_i2c_dma_complete;
+	dma_desc->callback_param = i2c_dev;
+	dmaengine_submit(dma_desc);
+	dma_async_issue_pending(chan);
+	return 0;
+}
+
+static void tegra_i2c_release_dma(struct tegra_i2c_dev *i2c_dev)
+{
+	if (i2c_dev->dma_buf) {
+		dma_free_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
+				  i2c_dev->dma_buf, i2c_dev->dma_phys);
+		i2c_dev->dma_buf = NULL;
+	}
+
+	if (i2c_dev->tx_dma_chan) {
+		dma_release_channel(i2c_dev->tx_dma_chan);
+		i2c_dev->tx_dma_chan = NULL;
+	}
+
+	if (i2c_dev->rx_dma_chan) {
+		dma_release_channel(i2c_dev->rx_dma_chan);
+		i2c_dev->rx_dma_chan = NULL;
+	}
+}
+
+static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
+{
+	struct dma_chan *chan;
+	u32 *dma_buf;
+	dma_addr_t dma_phys;
+	int err;
+
+	if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA) ||
+	    !i2c_dev->hw->has_apb_dma) {
+		err = -ENODEV;
+		goto err_out;
+	}
+
+	chan = dma_request_slave_channel_reason(i2c_dev->dev, "rx");
+	if (IS_ERR(chan)) {
+		err = PTR_ERR(chan);
+		goto err_out;
+	}
+
+	i2c_dev->rx_dma_chan = chan;
+
+	chan = dma_request_slave_channel_reason(i2c_dev->dev, "tx");
+	if (IS_ERR(chan)) {
+		err = PTR_ERR(chan);
+		goto err_out;
+	}
+
+	i2c_dev->tx_dma_chan = chan;
+
+	dma_buf = dma_alloc_coherent(i2c_dev->dev, i2c_dev->dma_buf_size,
+				     &dma_phys, GFP_KERNEL | __GFP_NOWARN);
+	if (!dma_buf) {
+		dev_err(i2c_dev->dev, "failed to allocate the DMA buffer\n");
+		err = -ENOMEM;
+		goto err_out;
+	}
+
+	i2c_dev->dma_buf = dma_buf;
+	i2c_dev->dma_phys = dma_phys;
+	return 0;
+
+err_out:
+	tegra_i2c_release_dma(i2c_dev);
+	if (err != -EPROBE_DEFER) {
+		dev_err(i2c_dev->dev, "can't use DMA, err: %d, using PIO\n",
+			err);
+		return 0;
+	}
+
+	return err;
+}
+
 static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
 {
 	unsigned long timeout = jiffies + HZ;
@@ -571,16 +706,6 @@  static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
 		i2c_writel(i2c_dev, 0x00, I2C_SL_ADDR2);
 	}
 
-	if (i2c_dev->hw->has_mst_fifo) {
-		val = I2C_MST_FIFO_CONTROL_TX_TRIG(8) |
-		      I2C_MST_FIFO_CONTROL_RX_TRIG(1);
-		i2c_writel(i2c_dev, val, I2C_MST_FIFO_CONTROL);
-	} else {
-		val = 7 << I2C_FIFO_CONTROL_TX_TRIG_SHIFT |
-			0 << I2C_FIFO_CONTROL_RX_TRIG_SHIFT;
-		i2c_writel(i2c_dev, val, I2C_FIFO_CONTROL);
-	}
-
 	err = tegra_i2c_flush_fifos(i2c_dev);
 	if (err)
 		goto err;
@@ -660,25 +785,37 @@  static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 	if (i2c_dev->hw->supports_bus_clear && (status & I2C_INT_BUS_CLR_DONE))
 		goto err;
 
-	if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
-		if (i2c_dev->msg_buf_remaining)
-			tegra_i2c_empty_rx_fifo(i2c_dev);
-		else
-			BUG();
-	}
+	if (!i2c_dev->is_curr_dma_xfer) {
+		if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
+			if (i2c_dev->msg_buf_remaining)
+				tegra_i2c_empty_rx_fifo(i2c_dev);
+			else
+				BUG();
+		}
 
-	if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
-		if (i2c_dev->msg_buf_remaining)
-			tegra_i2c_fill_tx_fifo(i2c_dev);
-		else
-			tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
+		if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
+			if (i2c_dev->msg_buf_remaining)
+				tegra_i2c_fill_tx_fifo(i2c_dev);
+			else
+				tegra_i2c_mask_irq(i2c_dev,
+						   I2C_INT_TX_FIFO_DATA_REQ);
+		}
 	}
 
 	i2c_writel(i2c_dev, status, I2C_INT_STATUS);
 	if (i2c_dev->is_dvc)
 		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
 
+	/*
+	 * During message read XFER_COMPLETE interrupt is triggered prior to
+	 * DMA completion and during message write XFER_COMPLETE interrupt is
+	 * triggered after DMA completion.
+	 * PACKETS_XFER_COMPLETE indicates completion of all bytes of transfer.
+	 * so forcing msg_buf_remaining to 0 in DMA mode.
+	 */
 	if (status & I2C_INT_PACKET_XFER_COMPLETE) {
+		if (i2c_dev->is_curr_dma_xfer)
+			i2c_dev->msg_buf_remaining = 0;
 		BUG_ON(i2c_dev->msg_buf_remaining);
 		complete(&i2c_dev->msg_complete);
 	}
@@ -694,12 +831,91 @@  static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
 	if (i2c_dev->is_dvc)
 		dvc_writel(i2c_dev, DVC_STATUS_I2C_DONE_INTR, DVC_STATUS);
 
+	if (i2c_dev->is_curr_dma_xfer) {
+		if (i2c_dev->msg_read)
+			dmaengine_terminate_async(i2c_dev->rx_dma_chan);
+		else
+			dmaengine_terminate_async(i2c_dev->tx_dma_chan);
+
+		complete(&i2c_dev->dma_complete);
+	}
+
 	complete(&i2c_dev->msg_complete);
 done:
 	spin_unlock(&i2c_dev->xfer_lock);
 	return IRQ_HANDLED;
 }
 
+static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
+				       size_t len)
+{
+	u32 val = 0, reg;
+	u8 dma_burst = 0;
+	struct dma_slave_config slv_config = {0};
+	struct dma_chan *chan;
+	int ret;
+	unsigned long reg_offset;
+
+	if (i2c_dev->hw->has_mst_fifo)
+		reg = I2C_MST_FIFO_CONTROL;
+	else
+		reg = I2C_FIFO_CONTROL;
+
+	if (i2c_dev->is_curr_dma_xfer) {
+		if (len & 0xF)
+			dma_burst = 1;
+		else if (len & 0x10)
+			dma_burst = 4;
+		else
+			dma_burst = 8;
+
+		if (i2c_dev->msg_read) {
+			chan = i2c_dev->rx_dma_chan;
+			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_RX_FIFO);
+			slv_config.src_addr = i2c_dev->base_phys + reg_offset;
+			slv_config.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+			slv_config.src_maxburst = dma_burst;
+
+			if (i2c_dev->hw->has_mst_fifo)
+				val |= I2C_MST_FIFO_CONTROL_RX_TRIG(dma_burst);
+			else
+				val |= I2C_FIFO_CONTROL_RX_TRIG(dma_burst);
+		} else {
+			chan = i2c_dev->tx_dma_chan;
+			reg_offset = tegra_i2c_reg_addr(i2c_dev, I2C_TX_FIFO);
+			slv_config.dst_addr = i2c_dev->base_phys + reg_offset;
+			slv_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+			slv_config.dst_maxburst = dma_burst;
+
+			if (i2c_dev->hw->has_mst_fifo)
+				val |= I2C_MST_FIFO_CONTROL_TX_TRIG(dma_burst);
+			else
+				val |= I2C_FIFO_CONTROL_TX_TRIG(dma_burst);
+		}
+
+		slv_config.device_fc = true;
+		ret = dmaengine_slave_config(chan, &slv_config);
+		if (ret < 0) {
+			dev_err(i2c_dev->dev, "DMA slave config failed: %d\n",
+				ret);
+			dev_err(i2c_dev->dev, "fallbacking to PIO\n");
+			tegra_i2c_release_dma(i2c_dev);
+			i2c_dev->is_curr_dma_xfer = false;
+		} else {
+			goto out;
+		}
+	}
+
+	if (i2c_dev->hw->has_mst_fifo)
+		val = I2C_MST_FIFO_CONTROL_TX_TRIG(8) |
+		      I2C_MST_FIFO_CONTROL_RX_TRIG(1);
+	else
+		val = I2C_FIFO_CONTROL_TX_TRIG(8) |
+		      I2C_FIFO_CONTROL_RX_TRIG(1);
+out:
+	i2c_writel(i2c_dev, val, reg);
+}
+
 static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev)
 {
 	int err;
@@ -744,6 +960,10 @@  static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 	u32 int_mask;
 	unsigned long time_left;
 	unsigned long flags;
+	size_t xfer_size;
+	u32 *buffer = NULL;
+	int err = 0;
+	bool dma;
 
 	tegra_i2c_flush_fifos(i2c_dev);
 
@@ -753,19 +973,58 @@  static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 	i2c_dev->msg_read = (msg->flags & I2C_M_RD);
 	reinit_completion(&i2c_dev->msg_complete);
 
+	if (i2c_dev->msg_read)
+		xfer_size = msg->len;
+	else
+		xfer_size = msg->len + I2C_PACKET_HEADER_SIZE;
+
+	xfer_size = ALIGN(xfer_size, BYTES_PER_FIFO_WORD);
+	i2c_dev->is_curr_dma_xfer = (xfer_size > I2C_PIO_MODE_MAX_LEN) &&
+				    i2c_dev->dma_buf;
+	tegra_i2c_config_fifo_trig(i2c_dev, xfer_size);
+	dma = i2c_dev->is_curr_dma_xfer;
+
 	spin_lock_irqsave(&i2c_dev->xfer_lock, flags);
 
 	int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST;
 	tegra_i2c_unmask_irq(i2c_dev, int_mask);
+	if (dma) {
+		if (i2c_dev->msg_read) {
+			dma_sync_single_for_device(i2c_dev->dev,
+						   i2c_dev->dma_phys,
+						   xfer_size,
+						   DMA_FROM_DEVICE);
+			err = tegra_i2c_dma_submit(i2c_dev, xfer_size);
+			if (err < 0) {
+				dev_err(i2c_dev->dev,
+					"starting RX DMA failed, err %d\n",
+					err);
+				goto unlock;
+			}
+
+		} else {
+			dma_sync_single_for_cpu(i2c_dev->dev,
+						i2c_dev->dma_phys,
+						xfer_size,
+						DMA_TO_DEVICE);
+			buffer = i2c_dev->dma_buf;
+		}
+	}
 
 	packet_header = (0 << PACKET_HEADER0_HEADER_SIZE_SHIFT) |
 			PACKET_HEADER0_PROTOCOL_I2C |
 			(i2c_dev->cont_id << PACKET_HEADER0_CONT_ID_SHIFT) |
 			(1 << PACKET_HEADER0_PACKET_ID_SHIFT);
-	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
+	if (dma && !i2c_dev->msg_read)
+		*buffer++ = packet_header;
+	else
+		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
 
 	packet_header = msg->len - 1;
-	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
+	if (dma && !i2c_dev->msg_read)
+		*buffer++ = packet_header;
+	else
+		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
 
 	packet_header = I2C_HEADER_IE_ENABLE;
 	if (end_state == MSG_END_CONTINUE)
@@ -782,23 +1041,81 @@  static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 		packet_header |= I2C_HEADER_CONT_ON_NAK;
 	if (msg->flags & I2C_M_RD)
 		packet_header |= I2C_HEADER_READ;
-	i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
-
-	if (!(msg->flags & I2C_M_RD))
-		tegra_i2c_fill_tx_fifo(i2c_dev);
+	if (dma && !i2c_dev->msg_read)
+		*buffer++ = packet_header;
+	else
+		i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);
+
+	if (!i2c_dev->msg_read) {
+		if (dma) {
+			memcpy(buffer, msg->buf, msg->len);
+			dma_sync_single_for_device(i2c_dev->dev,
+						   i2c_dev->dma_phys,
+						   xfer_size,
+						   DMA_TO_DEVICE);
+			err = tegra_i2c_dma_submit(i2c_dev, xfer_size);
+			if (err < 0) {
+				dev_err(i2c_dev->dev,
+					"starting TX DMA failed, err %d\n",
+					err);
+				goto unlock;
+			}
+
+		} else {
+			tegra_i2c_fill_tx_fifo(i2c_dev);
+		}
+	}
 
 	if (i2c_dev->hw->has_per_pkt_xfer_complete_irq)
 		int_mask |= I2C_INT_PACKET_XFER_COMPLETE;
-	if (msg->flags & I2C_M_RD)
-		int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
-	else if (i2c_dev->msg_buf_remaining)
-		int_mask |= I2C_INT_TX_FIFO_DATA_REQ;
+
+	if (!dma) {
+		if (msg->flags & I2C_M_RD)
+			int_mask |= I2C_INT_RX_FIFO_DATA_REQ;
+		else if (i2c_dev->msg_buf_remaining)
+			int_mask |= I2C_INT_TX_FIFO_DATA_REQ;
+	}
 
 	tegra_i2c_unmask_irq(i2c_dev, int_mask);
-	spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags);
 	dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n",
 		i2c_readl(i2c_dev, I2C_INT_MASK));
 
+unlock:
+	spin_unlock_irqrestore(&i2c_dev->xfer_lock, flags);
+
+	if (dma) {
+		if (err)
+			return err;
+
+		time_left = wait_for_completion_timeout(
+						&i2c_dev->dma_complete,
+						TEGRA_I2C_TIMEOUT);
+
+		if (time_left == 0) {
+			dev_err(i2c_dev->dev, "DMA transfer timeout\n");
+			dmaengine_terminate_sync(i2c_dev->msg_read ?
+						  i2c_dev->rx_dma_chan :
+						  i2c_dev->tx_dma_chan);
+			tegra_i2c_init(i2c_dev);
+			return -ETIMEDOUT;
+		}
+
+		if (i2c_dev->msg_read && i2c_dev->msg_err == I2C_ERR_NONE) {
+			dma_sync_single_for_cpu(i2c_dev->dev,
+						i2c_dev->dma_phys,
+						xfer_size,
+						DMA_FROM_DEVICE);
+			memcpy(i2c_dev->msg_buf, i2c_dev->dma_buf,
+			       msg->len);
+		}
+
+		if (i2c_dev->msg_err != I2C_ERR_NONE) {
+			dmaengine_synchronize(i2c_dev->msg_read ?
+					      i2c_dev->rx_dma_chan :
+					      i2c_dev->tx_dma_chan);
+		}
+	}
+
 	time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
 						TEGRA_I2C_TIMEOUT);
 	tegra_i2c_mask_irq(i2c_dev, int_mask);
@@ -814,6 +1131,7 @@  static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 		time_left, completion_done(&i2c_dev->msg_complete),
 		i2c_dev->msg_err);
 
+	i2c_dev->is_curr_dma_xfer = false;
 	if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
 		return 0;
 
@@ -920,6 +1238,7 @@  static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = false,
+	.has_apb_dma = true,
 };
 
 static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
@@ -935,6 +1254,7 @@  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = false,
+	.has_apb_dma = true,
 };
 
 static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
@@ -950,6 +1270,7 @@  static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
+	.has_apb_dma = true,
 };
 
 static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
@@ -965,6 +1286,7 @@  static const struct tegra_i2c_hw_feature tegra124_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
+	.has_apb_dma = true,
 };
 
 static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
@@ -980,6 +1302,7 @@  static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
 	.has_mst_fifo = false,
 	.quirks = &tegra_i2c_quirks,
 	.supports_bus_clear = true,
+	.has_apb_dma = true,
 };
 
 static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
@@ -995,6 +1318,7 @@  static const struct tegra_i2c_hw_feature tegra194_i2c_hw = {
 	.has_mst_fifo = true,
 	.quirks = &tegra194_i2c_quirks,
 	.supports_bus_clear = true,
+	.has_apb_dma = false,
 };
 
 /* Match table for of_platform binding */
@@ -1017,11 +1341,13 @@  static int tegra_i2c_probe(struct platform_device *pdev)
 	struct clk *div_clk;
 	struct clk *fast_clk;
 	void __iomem *base;
+	phys_addr_t base_phys;
 	int irq;
 	int ret = 0;
 	int clk_multiplier = I2C_CLK_MULTIPLIER_STD_FAST_MODE;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base_phys = res->start;
 	base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(base))
 		return PTR_ERR(base);
@@ -1044,6 +1370,7 @@  static int tegra_i2c_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	i2c_dev->base = base;
+	i2c_dev->base_phys = base_phys;
 	i2c_dev->div_clk = div_clk;
 	i2c_dev->adapter.algo = &tegra_i2c_algo;
 	i2c_dev->adapter.retries = 1;
@@ -1063,7 +1390,9 @@  static int tegra_i2c_probe(struct platform_device *pdev)
 	i2c_dev->is_dvc = of_device_is_compatible(pdev->dev.of_node,
 						  "nvidia,tegra20-i2c-dvc");
 	i2c_dev->adapter.quirks = i2c_dev->hw->quirks;
+	i2c_dev->dma_buf_size = i2c_dev->adapter.quirks->max_write_len;
 	init_completion(&i2c_dev->msg_complete);
+	init_completion(&i2c_dev->dma_complete);
 	spin_lock_init(&i2c_dev->xfer_lock);
 
 	if (!i2c_dev->hw->has_single_clk_source) {
@@ -1124,6 +1453,10 @@  static int tegra_i2c_probe(struct platform_device *pdev)
 		}
 	}
 
+	ret = tegra_i2c_init_dma(i2c_dev);
+	if (ret < 0)
+		goto disable_div_clk;
+
 	ret = tegra_i2c_init(i2c_dev);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to initialize i2c controller\n");
@@ -1188,6 +1521,7 @@  static int tegra_i2c_remove(struct platform_device *pdev)
 	if (!i2c_dev->hw->has_single_clk_source)
 		clk_unprepare(i2c_dev->fast_clk);
 
+	tegra_i2c_release_dma(i2c_dev);
 	return 0;
 }
 
@@ -1211,18 +1545,7 @@  static struct platform_driver tegra_i2c_driver = {
 	},
 };
 
-static int __init tegra_i2c_init_driver(void)
-{
-	return platform_driver_register(&tegra_i2c_driver);
-}
-
-static void __exit tegra_i2c_exit_driver(void)
-{
-	platform_driver_unregister(&tegra_i2c_driver);
-}
-
-subsys_initcall(tegra_i2c_init_driver);
-module_exit(tegra_i2c_exit_driver);
+module_platform_driver(tegra_i2c_driver);
 
 MODULE_DESCRIPTION("nVidia Tegra2 I2C Bus Controller driver");
 MODULE_AUTHOR("Colin Cross");