Patchwork i2c-designware: fix RX FIFO overrun

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Submitter Josef Ahmad
Date April 24, 2013, 10:11 a.m.
Message ID <alpine.DEB.2.02.1304241110480.32505@localhost>
Download mbox | patch
Permalink /patch/239163/
State Superseded
Headers show

Comments

Josef Ahmad - April 24, 2013, 10:11 a.m.
From 8a4773d0c0df6fe2e816ad37fde30a2d90a1ad31 Mon Sep 17 00:00:00 2001
From: Josef Ahmad <josef.ahmad@linux.intel.com>
Date: Fri, 19 Apr 2013 17:28:10 +0100
Subject: [PATCH] i2c-designware: fix RX FIFO overrun

i2c_dw_xfer_msg() pushes a number of bytes to transmit/receive
to/from the bus into the TX FIFO.
For master-rx transactions, the maximum amount of data that can be
received is calculated depending solely on TX and RX FIFO load.

This is racy - TX FIFO may contain master-rx data yet to be
processed, which will eventually land into the RX FIFO. This
data is not taken into account and the function may request more
data than the controller is actually capable of storing.

This patch ensures the driver takes into account the outstanding
master-rx data in TX FIFO to prevent RX FIFO overrun.

Signed-off-by: Josef Ahmad <josef.ahmad@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
  drivers/i2c/busses/i2c-designware-core.c |   11 ++++++++++-
  drivers/i2c/busses/i2c-designware-core.h |    2 ++
  2 files changed, 12 insertions(+), 1 deletions(-)
Wolfram Sang - April 25, 2013, 5:43 p.m.
On Wed, Apr 24, 2013 at 11:11:38AM +0100, Josef Ahmad wrote:
> From 8a4773d0c0df6fe2e816ad37fde30a2d90a1ad31 Mon Sep 17 00:00:00 2001
> From: Josef Ahmad <josef.ahmad@linux.intel.com>
> Date: Fri, 19 Apr 2013 17:28:10 +0100
> Subject: [PATCH] i2c-designware: fix RX FIFO overrun
> 
> i2c_dw_xfer_msg() pushes a number of bytes to transmit/receive
> to/from the bus into the TX FIFO.
> For master-rx transactions, the maximum amount of data that can be
> received is calculated depending solely on TX and RX FIFO load.
> 
> This is racy - TX FIFO may contain master-rx data yet to be
> processed, which will eventually land into the RX FIFO. This
> data is not taken into account and the function may request more
> data than the controller is actually capable of storing.
> 
> This patch ensures the driver takes into account the outstanding
> master-rx data in TX FIFO to prevent RX FIFO overrun.
> 
> Signed-off-by: Josef Ahmad <josef.ahmad@linux.intel.com>
> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Still can't apply :( Whitespace problems in the patch context :(

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Josef Ahmad - May 8, 2013, 1:31 p.m.
Sorry for late reply.
Bad UA configuration. Will resend straight away.

Thanks,

Josef

On Thu, 25 Apr 2013, Wolfram Sang wrote:

>
> Still can't apply :( Whitespace problems in the patch context :(
>
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Patch

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 21fbb34..1f06c8e 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -448,8 +448,14 @@  i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
  				cmd |= BIT(9);

  			if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
+
+				/* avoid rx buffer overrun */
+				if (rx_limit - dev->rx_outstanding <= 0)
+					break;
+
  				dw_writel(dev, cmd | 0x100, DW_IC_DATA_CMD);
  				rx_limit--;
+				dev->rx_outstanding++;
  			} else
  				dw_writel(dev, cmd | *buf++, DW_IC_DATA_CMD);
  			tx_limit--; buf_len--;
@@ -502,8 +508,10 @@  i2c_dw_read(struct dw_i2c_dev *dev)

  		rx_valid = dw_readl(dev, DW_IC_RXFLR);

-		for (; len > 0 && rx_valid > 0; len--, rx_valid--)
+		for (; len > 0 && rx_valid > 0; len--, rx_valid--) {
  			*buf++ = dw_readl(dev, DW_IC_DATA_CMD);
+			dev->rx_outstanding--;
+		}

  		if (len > 0) {
  			dev->status |= STATUS_READ_IN_PROGRESS;
@@ -561,6 +569,7 @@  i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
  	dev->msg_err = 0;
  	dev->status = STATUS_IDLE;
  	dev->abort_source = 0;
+	dev->rx_outstanding = 0;

  	ret = i2c_dw_wait_bus_not_busy(dev);
  	if (ret < 0)
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 9c1840e..e761ad1 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -60,6 +60,7 @@ 
   * @adapter: i2c subsystem adapter node
   * @tx_fifo_depth: depth of the hardware tx fifo
   * @rx_fifo_depth: depth of the hardware rx fifo
+ * @rx_outstanding: current master-rx elements in tx fifo
   */
  struct dw_i2c_dev {
  	struct device		*dev;
@@ -88,6 +89,7 @@  struct dw_i2c_dev {
  	u32			master_cfg;
  	unsigned int		tx_fifo_depth;
  	unsigned int		rx_fifo_depth;
+	int			rx_outstanding;
  };

  #define ACCESS_SWAP		0x00000001