Re: [PATCH v5 5/7] ARM: davinci: i2c: add OF support

[Sekhar Nori <nsekhar-l0cyMroinI0@public.gmane.org>]

Hi Heiko,

On 5/30/2012 3:49 PM, Heiko Schocher wrote:
> add of support for the davinci i2c driver.
> 
> Signed-off-by: Heiko Schocher <hs-ynQEQJNshbs@public.gmane.org>
> Cc: davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org
> Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
> Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> Cc: Ben Dooks <ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>
> Cc: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> Cc: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
> Cc: Sekhar Nori <nsekhar-l0cyMroinI0@public.gmane.org>
> Cc: Wolfgang Denk <wd-ynQEQJNshbs@public.gmane.org>
> Cc: Sylwester Nawrocki <s.nawrocki-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
> 
> ---
> - changes for v2:
> - add comments from Sylwester Nawrocki <s.nawrocki-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>:
>   - use "cell-index" instead "id"
>   - OF_DEV_AUXDATA in the machine code, instead pre-define platform
>     device name
> - add comment from Grant Likely:
>   - removed "id" resp. "cell-index" completely
>   - fixed documentation
>   - use of_match_ptr()
>   - use devm_kzalloc() for allocating plattform data mem
>   - fixed a whitespace issue
> - no changes for v3
> - changes for v4
>   remove "pinmux-handle" property as discussed here:
>   http://www.spinics.net/lists/arm-kernel/msg175701.html
>   with Nori Sekhar
> 
> - changes for v5
>   add comments from Grant Likely:
>   - do not change value of dev->dev->platform_data, instead
>     hold a copy in davinci_i2c_dev.
> 
>  .../devicetree/bindings/arm/davinci/i2c.txt        |   31 ++++++++++++
>  drivers/i2c/busses/i2c-davinci.c                   |   49 ++++++++++++++++++--
>  2 files changed, 76 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/arm/davinci/i2c.txt
> 
> diff --git a/Documentation/devicetree/bindings/arm/davinci/i2c.txt b/Documentation/devicetree/bindings/arm/davinci/i2c.txt
> new file mode 100644
> index 0000000..e98a025
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/davinci/i2c.txt
> @@ -0,0 +1,31 @@
> +* Texas Instruments Davinci I2C
> +
> +This file provides information, what the device node for the
> +davinci i2c interface contain.
> +
> +Required properties:
> +- compatible: "ti,davinci-i2c";
> +- reg : Offset and length of the register set for the device
> +
> +Recommended properties :
> +- interrupts : <a> standard interrupt property.
> +- clock-frequency : desired I2C bus clock frequency in Hz.
> +
> +Optional properties:
> +- bus-delay: bus delay in usec
> +
> +Example (enbw_cmc board):
> +	i2c@1c22000 {
> +		compatible = "ti,davinci-i2c";
> +		reg = <0x22000 0x1000>;
> +		clock-frequency = <100000>;
> +		interrupts = <15>;
> +		interrupt-parent = <&intc>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		dtt@48 {
> +				compatible = "national,lm75";
> +				reg = <0x48>;
> +			};
> +	};
> diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
> index a76d85f..4e7a966 100644
> --- a/drivers/i2c/busses/i2c-davinci.c
> +++ b/drivers/i2c/busses/i2c-davinci.c
> @@ -38,9 +38,12 @@
>  #include <linux/slab.h>
>  #include <linux/cpufreq.h>
>  #include <linux/gpio.h>
> +#include <linux/of_i2c.h>
> +#include <linux/of_device.h>
>  
>  #include <mach/hardware.h>
>  #include <mach/i2c.h>
> +#include <mach/mux.h>

Seems like a stray change. I was able to build and use just fine
without this include.

>  
>  /* ----- global defines ----------------------------------------------- */
>  
> @@ -114,6 +117,7 @@ struct davinci_i2c_dev {
>  	struct completion	xfr_complete;
>  	struct notifier_block	freq_transition;
>  #endif
> +	struct davinci_i2c_platform_data *pdata;
>  };
>  
>  /* default platform data to use if not supplied in the platform_device */
> @@ -149,13 +153,22 @@ static void generic_i2c_clock_pulse(unsigned int scl_pin)
>  	}
>  }
>  
> +static struct davinci_i2c_platform_data
> +		*i2c_get_plattformdata(struct davinci_i2c_dev *dev)
> +{
> +	if (dev->dev->platform_data == NULL)
> +		return dev->pdata;
> +
> +	return dev->dev->platform_data;
> +}

It seems to me that if we setup the newly introduced dev->pdata
member correctly once in probe, there should not be a need for this
function. We can also eliminate multiple checks for pdata in code.
See below for more.

> +
>  /* This routine does i2c bus recovery as specified in the
>   * i2c protocol Rev. 03 section 3.16 titled "Bus clear"
>   */
>  static void i2c_recover_bus(struct davinci_i2c_dev *dev)
>  {
>  	u32 flag = 0;
> -	struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
> +	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
>  
>  	dev_err(dev->dev, "initiating i2c bus recovery\n");
>  	/* Send NACK to the slave */
> @@ -187,7 +200,7 @@ static inline void davinci_i2c_reset_ctrl(struct davinci_i2c_dev *i2c_dev,
>  
>  static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
>  {
> -	struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
> +	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
>  	u16 psc;
>  	u32 clk;
>  	u32 d;
> @@ -235,7 +248,7 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
>   */
>  static int i2c_davinci_init(struct davinci_i2c_dev *dev)
>  {
> -	struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
> +	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
>  
>  	if (!pdata)
>  		pdata = &davinci_i2c_platform_data_default;
> @@ -308,7 +321,7 @@ static int
>  i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
>  {
>  	struct davinci_i2c_dev *dev = i2c_get_adapdata(adap);
> -	struct davinci_i2c_platform_data *pdata = dev->dev->platform_data;
> +	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
>  	u32 flag;
>  	u16 w;
>  	int r;
> @@ -635,6 +648,12 @@ static struct i2c_algorithm i2c_davinci_algo = {
>  	.functionality	= i2c_davinci_func,
>  };
>  
> +static const struct of_device_id davinci_i2c_of_match[] = {
> +	{.compatible = "ti,davinci-i2c", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, davinci_i2c_of_match);
> +
>  static int davinci_i2c_probe(struct platform_device *pdev)
>  {
>  	struct davinci_i2c_dev *dev;
> @@ -676,6 +695,25 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>  	dev->irq = irq->start;
>  	platform_set_drvdata(pdev, dev);
>  
> +	if ((dev->dev->platform_data == NULL) &&
> +		(pdev->dev.of_node)) {
> +		u32 prop;
> +
> +		dev->pdata = devm_kzalloc(&pdev->dev,
> +			sizeof(struct davinci_i2c_platform_data), GFP_KERNEL);
> +		if (!dev->pdata) {
> +			r = -ENOMEM;
> +			goto err_free_mem;
> +		}
> +		memcpy(dev->pdata, &davinci_i2c_platform_data_default,
> +			sizeof(struct davinci_i2c_platform_data));
> +		if (!of_property_read_u32(pdev->dev.of_node, "clock-frequency",
> +			&prop))
> +			dev->pdata->bus_freq = prop / 1000;
> +		if (!of_property_read_u32(pdev->dev.of_node, "bus-delay",
> +			&prop))
> +			dev->pdata->bus_delay = prop;

You are leaving out two other platform data members (the gpio pins
corresponding to data and clock) from DT data. We should be able to
get that information from DT too, right?

So, I took this patch and tried to see if pdata maintenance can be
simplified and came with the diff below. Can you have a look and see
if this makes sense? I tested this using i2cdetect both with and
without DT.

Thanks,
Sekhar

---8<---
diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index 16d7645..d07c207 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -153,22 +153,13 @@ static void generic_i2c_clock_pulse(unsigned int scl_pin)
 	}
 }
 
-static struct davinci_i2c_platform_data
-		*i2c_get_plattformdata(struct davinci_i2c_dev *dev)
-{
-	if (dev->dev->platform_data == NULL)
-		return dev->pdata;
-
-	return dev->dev->platform_data;
-}
-
 /* This routine does i2c bus recovery as specified in the
  * i2c protocol Rev. 03 section 3.16 titled "Bus clear"
  */
 static void i2c_recover_bus(struct davinci_i2c_dev *dev)
 {
 	u32 flag = 0;
-	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
+	struct davinci_i2c_platform_data *pdata = dev->pdata;
 
 	dev_err(dev->dev, "initiating i2c bus recovery\n");
 	/* Send NACK to the slave */
@@ -176,8 +167,7 @@ static void i2c_recover_bus(struct davinci_i2c_dev *dev)
 	flag |=  DAVINCI_I2C_MDR_NACK;
 	/* write the data into mode register */
 	davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
-	if (pdata)
-		generic_i2c_clock_pulse(pdata->scl_pin);
+	generic_i2c_clock_pulse(pdata->scl_pin);
 	/* Send STOP */
 	flag = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
 	flag |= DAVINCI_I2C_MDR_STP;
@@ -200,7 +190,7 @@ static inline void davinci_i2c_reset_ctrl(struct davinci_i2c_dev *i2c_dev,
 
 static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
 {
-	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
+	struct davinci_i2c_platform_data *pdata = dev->pdata;
 	u16 psc;
 	u32 clk;
 	u32 d;
@@ -248,10 +238,7 @@ static void i2c_davinci_calc_clk_dividers(struct davinci_i2c_dev *dev)
  */
 static int i2c_davinci_init(struct davinci_i2c_dev *dev)
 {
-	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
-
-	if (!pdata)
-		pdata = &davinci_i2c_platform_data_default;
+	struct davinci_i2c_platform_data *pdata = dev->pdata;
 
 	/* put I2C into reset */
 	davinci_i2c_reset_ctrl(dev, 0);
@@ -321,13 +308,11 @@ static int
 i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
 {
 	struct davinci_i2c_dev *dev = i2c_get_adapdata(adap);
-	struct davinci_i2c_platform_data *pdata = i2c_get_plattformdata(dev);
+	struct davinci_i2c_platform_data *pdata = dev->pdata;
 	u32 flag;
 	u16 w;
 	int r;
 
-	if (!pdata)
-		pdata = &davinci_i2c_platform_data_default;
 	/* Introduce a delay, required for some boards (e.g Davinci EVM) */
 	if (pdata->bus_delay)
 		udelay(pdata->bus_delay);
@@ -693,10 +678,10 @@ static int davinci_i2c_probe(struct platform_device *pdev)
 #endif
 	dev->dev = get_device(&pdev->dev);
 	dev->irq = irq->start;
+	dev->pdata = dev->dev->platform_data;
 	platform_set_drvdata(pdev, dev);
 
-	if ((dev->dev->platform_data == NULL) &&
-		(pdev->dev.of_node)) {
+	if (!dev->pdata && pdev->dev.of_node) {
 		u32 prop;
 
 		dev->pdata = devm_kzalloc(&pdev->dev,
@@ -713,7 +698,10 @@ static int davinci_i2c_probe(struct platform_device *pdev)
 		if (!of_property_read_u32(pdev->dev.of_node, "bus-delay",
 			&prop))
 			dev->pdata->bus_delay = prop;
+	} else if (!dev->pdata) {
+		dev->pdata = &davinci_i2c_platform_data_default;
 	}
+
 	dev->clk = clk_get(&pdev->dev, NULL);
 	if (IS_ERR(dev->clk)) {
 		r = -ENODEV;