[1/2] i2c: tegra: enable multi master mode

Enable multi-master mode in I2C_CNFG reg based on hw features.
Using single/multi-master mode bit introduced for Tegra210,
whereas multi-master mode is enabled by default in HW for T124 and
earlier Tegra SOC. Enabling this bit doesn't explicitly start
treating the bus has having multiple masters, but will start
checking for arbitration lost and reporting when it occurs.

The Tegra210 I2C controller supports single/multi master mode.
Add chipdata for Tegra210 and its compatibility string so that
Tegra210 will select data that enables multi master mode correctly.

Add "nvidia,multimaster-mode" property to enable multimaster specific
prerequisites:
1. Enable 1st level clock always set.
2. Disable 2nd level clock gating (slcg which is supported from
   T124 SOC and later chips)

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
---
 drivers/i2c/busses/i2c-tegra.c | 70 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 64 insertions(+), 6 deletions(-)

On Mon, Mar 14, 2016 at 02:14:33PM +0530, Shardar Shariff Md wrote:
> Enable multi-master mode in I2C_CNFG reg based on hw features.
> Using single/multi-master mode bit introduced for Tegra210,
> whereas multi-master mode is enabled by default in HW for T124 and
> earlier Tegra SOC. Enabling this bit doesn't explicitly start
> treating the bus has having multiple masters, but will start
> checking for arbitration lost and reporting when it occurs.
> 
> The Tegra210 I2C controller supports single/multi master mode.
> Add chipdata for Tegra210 and its compatibility string so that
> Tegra210 will select data that enables multi master mode correctly.
> 
> Add "nvidia,multimaster-mode" property to enable multimaster specific
> prerequisites:

Please check Documentation/devicetree/bindings/i2c/i2c.txt. There is a
generic "multi-master" binding already.

> 1. Enable 1st level clock always set.
> 2. Disable 2nd level clock gating (slcg which is supported from
>    T124 SOC and later chips)
> 
> Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 70 ++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 64 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index efba1eb..ce99d02 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -38,6 +38,7 @@
>  #define I2C_CNFG_DEBOUNCE_CNT_SHIFT		12
>  #define I2C_CNFG_PACKET_MODE_EN			(1<<10)
>  #define I2C_CNFG_NEW_MASTER_FSM			(1<<11)
> +#define I2C_CNFG_MULTI_MASTER_MODE		(1<<17)
>  #define I2C_STATUS				0x01C
>  #define I2C_SL_CNFG				0x020
>  #define I2C_SL_CNFG_NACK			(1<<1)
> @@ -133,6 +134,8 @@ struct tegra_i2c_hw_feature {
>  	bool has_single_clk_source;
>  	int clk_divisor_hs_mode;
>  	int clk_divisor_std_fast_mode;
> +	bool has_multi_master_mode;
> +	bool has_slcg_override_reg;
>  };
>  
>  /**
> @@ -173,6 +176,7 @@ struct tegra_i2c_dev {
>  	int msg_read;
>  	u32 bus_clk_rate;
>  	bool is_suspended;
> +	bool is_multimaster_mode;
>  };
>  
>  static void dvc_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned long reg)
> @@ -185,6 +189,9 @@ static u32 dvc_readl(struct tegra_i2c_dev *i2c_dev, unsigned long reg)
>  	return readl(i2c_dev->base + reg);
>  }
>  
> +#define I2C_CLKEN_OVERRIDE			0x090
> +#define I2C_MST_CORE_CLKEN_OVR			(1 << 0)
> +
>  /*
>   * i2c_writel and i2c_readl will offset the register if necessary to talk
>   * to the I2C block inside the DVC block
> @@ -424,6 +431,10 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>  
>  	val = I2C_CNFG_NEW_MASTER_FSM | I2C_CNFG_PACKET_MODE_EN |
>  		(0x2 << I2C_CNFG_DEBOUNCE_CNT_SHIFT);
> +
> +	if (i2c_dev->hw->has_multi_master_mode)
> +		val |= I2C_CNFG_MULTI_MASTER_MODE;
> +
>  	i2c_writel(i2c_dev, val, I2C_CNFG);
>  	i2c_writel(i2c_dev, 0, I2C_INT_MASK);
>  
> @@ -449,6 +460,9 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>  	if (tegra_i2c_flush_fifos(i2c_dev))
>  		err = -ETIMEDOUT;
>  
> +	if (i2c_dev->is_multimaster_mode && i2c_dev->hw->has_slcg_override_reg)
> +		i2c_writel(i2c_dev, I2C_MST_CORE_CLKEN_OVR, I2C_CLKEN_OVERRIDE);
> +
>  	tegra_i2c_clock_disable(i2c_dev);
>  
>  	if (i2c_dev->irq_disabled) {
> @@ -660,6 +674,20 @@ static u32 tegra_i2c_func(struct i2c_adapter *adap)
>  	return ret;
>  }
>  
> +static void tegra_i2c_parse_dt(struct tegra_i2c_dev *i2c_dev)
> +{
> +	struct device_node *np = i2c_dev->dev->of_node;
> +	int ret;
> +
> +	ret = of_property_read_u32(np, "clock-frequency",
> +			&i2c_dev->bus_clk_rate);
> +	if (ret)
> +		i2c_dev->bus_clk_rate = 100000; /* default clock rate */
> +
> +	i2c_dev->is_multimaster_mode = of_property_read_bool(np,
> +			"nvidia,multimaster-mode");
> +}
> +
>  static const struct i2c_algorithm tegra_i2c_algo = {
>  	.master_xfer	= tegra_i2c_xfer,
>  	.functionality	= tegra_i2c_func,
> @@ -671,6 +699,8 @@ static const struct tegra_i2c_hw_feature tegra20_i2c_hw = {
>  	.has_single_clk_source = false,
>  	.clk_divisor_hs_mode = 3,
>  	.clk_divisor_std_fast_mode = 0,
> +	.has_multi_master_mode = false,
> +	.has_slcg_override_reg = false,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -679,6 +709,8 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>  	.has_single_clk_source = false,
>  	.clk_divisor_hs_mode = 3,
>  	.clk_divisor_std_fast_mode = 0,
> +	.has_multi_master_mode = false,
> +	.has_slcg_override_reg = false,
>  };
>  
>  static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
> @@ -687,10 +719,25 @@ static const struct tegra_i2c_hw_feature tegra114_i2c_hw = {
>  	.has_single_clk_source = true,
>  	.clk_divisor_hs_mode = 1,
>  	.clk_divisor_std_fast_mode = 0x19,
> +	.has_multi_master_mode = false,
> +	.has_slcg_override_reg = false,
>  };
>  
> +static const struct tegra_i2c_hw_feature tegra210_i2c_hw = {
> +	.has_continue_xfer_support = true,
> +	.has_per_pkt_xfer_complete_irq = true,
> +	.has_single_clk_source = true,
> +	.clk_divisor_hs_mode = 1,
> +	.clk_divisor_std_fast_mode = 0x19,
> +	.has_config_load_reg = true,
> +	.has_multi_master_mode = true,
> +	.has_slcg_override_reg = true,
> +};
> +
> +
>  /* Match table for of_platform binding */
>  static const struct of_device_id tegra_i2c_of_match[] = {
> +	{ .compatible = "nvidia,tegra210-i2c", .data = &tegra210_i2c_hw, },
>  	{ .compatible = "nvidia,tegra114-i2c", .data = &tegra114_i2c_hw, },
>  	{ .compatible = "nvidia,tegra30-i2c", .data = &tegra30_i2c_hw, },
>  	{ .compatible = "nvidia,tegra20-i2c", .data = &tegra20_i2c_hw, },
> @@ -745,10 +792,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  		return PTR_ERR(i2c_dev->rst);
>  	}
>  
> -	ret = of_property_read_u32(i2c_dev->dev->of_node, "clock-frequency",
> -					&i2c_dev->bus_clk_rate);
> -	if (ret)
> -		i2c_dev->bus_clk_rate = 100000; /* default clock rate */
> +	tegra_i2c_parse_dt(i2c_dev);
>  
>  	i2c_dev->hw = &tegra20_i2c_hw;
>  
> @@ -796,6 +840,13 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  		goto unprepare_fast_clk;
>  	}
>  
> +	if (i2c_dev->is_multimaster_mode) {
> +		ret = clk_enable(i2c_dev->div_clk);
> +		dev_err(i2c_dev->dev, "div_clk enable failed %d\n",
> +				ret);
> +		goto unprepare_div_clk;
> +	}
> +
>  	ret = tegra_i2c_init(i2c_dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Failed to initialize i2c controller");
> @@ -806,7 +857,7 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  			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 unprepare_div_clk;
> +		goto disable_div_clk;
>  	}
>  
>  	i2c_set_adapdata(&i2c_dev->adapter, i2c_dev);
> @@ -822,11 +873,15 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  	ret = i2c_add_numbered_adapter(&i2c_dev->adapter);
>  	if (ret) {
>  		dev_err(&pdev->dev, "Failed to add I2C adapter\n");
> -		goto unprepare_div_clk;
> +		goto disable_div_clk;
>  	}
>  
>  	return 0;
>  
> +disable_div_clk:
> +	if (i2c_dev->is_multimaster_mode)
> +		clk_disable(i2c_dev->div_clk);
> +
>  unprepare_div_clk:
>  	clk_unprepare(i2c_dev->div_clk);
>  
> @@ -842,6 +897,9 @@ static int tegra_i2c_remove(struct platform_device *pdev)
>  	struct tegra_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
>  	i2c_del_adapter(&i2c_dev->adapter);
>  
> +	if (i2c_dev->is_multimaster_mode)
> +		clk_disable(i2c_dev->div_clk);
> +
>  	clk_unprepare(i2c_dev->div_clk);
>  	if (!i2c_dev->hw->has_single_clk_source)
>  		clk_unprepare(i2c_dev->fast_clk);
> -- 
> 1.8.1.5
>