Message-ID: <20110216054956.GD11684@angua.secretlab.ca>
Date:	Tue, 15 Feb 2011 22:49:56 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Thomas Chou <thomas@...ron.com.tw>
Cc:	Ben Dooks <ben-linux@...ff.org>, linux-kernel@...r.kernel.org,
	nios2-dev@...c.et.ntust.edu.tw,
	devicetree-discuss@...ts.ozlabs.org, linux-i2c@...r.kernel.org,
	Albert Herranz <albert_herranz@...oo.es>
Subject: Re: [PATCH v5] i2c-gpio: add devicetree support

On Mon, Feb 14, 2011 at 10:30:10AM +0800, Thomas Chou wrote:
> From: Albert Herranz <albert_herranz@...oo.es>
> 
> This patch adds devicetree support to i2c-gpio driver. The allocation
> of local data is integrated to a private structure, and use devm_*
> helper for easy cleanup.
> 
> It is base on an earlier patch for gc-linux from
> Albert Herranz <albert_herranz@...oo.es>.
> 
> Signed-off-by: Thomas Chou <thomas@...ron.com.tw>
> CC: Albert Herranz <albert_herranz@...oo.es>
> Acked-by: Haavard Skinnemoen <hskinnemoen@...il.com>

One minor nitpick below, but I'd be fine with cleaning that up via a
followup patch.  This one looks correct to me.

Acked-by: Grant Likely <grant.likely@...retlab.ca>

Ben, this one depends on a patch in my devicetree/next tree.  How do
you want to handle it?

g.

> ---
> for v2.6.39
> v2 move of nodes probing to a hook, which will be optimized out
>      when devicetree is not used.
>    use linux/gpio.h.
>    move binding doc to i2c/i2c-gpio.txt.
> v3 use speed-hz instead of udelay in dts binding.
>    condition the devicetree probe.
> v4 simplify private allocation.
> v5 condition module device table export for of.
> 
>  Documentation/devicetree/bindings/i2c/i2c-gpio.txt |   40 +++++++
>  drivers/i2c/busses/i2c-gpio.c                      |  113 ++++++++++++++++----
>  2 files changed, 133 insertions(+), 20 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-gpio.txt b/Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> new file mode 100644
> index 0000000..38ef4f2
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-gpio.txt
> @@ -0,0 +1,40 @@
> +GPIO-based I2C
> +
> +Required properties:
> +- compatible : should be "i2c-gpio".
> +- gpios : should specify GPIOs used for SDA and SCL lines, in that order.
> +Optional properties:
> +- sda-is-open-drain : present if SDA gpio is open-drain.
> +- scl-is-open-drain : present if SCL gpio is open-drain.
> +- scl-is-output-only : present if the output driver for SCL cannot be
> +	turned off. this will prevent clock stretching from working.
> +- speed-hz : SCL frequency.
> +- timeout : clock stretching timeout in milliseconds.
> +
> +Example:
> +
> +gpio0: starlet-gpio@...000c0 {
> +	compatible = "nintendo,starlet-gpio";
> +	reg = <0d8000c0 4>;
> +	gpio-controller;
> +	#gpio-cells = <2>;
> +};
> +
> +i2c-video {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	compatible = "i2c-gpio";
> +
> +	gpios = <&gpio0 10 0	/* SDA line */
> +		 &gpio0 11 0	/* SCL line */
> +		>;
> +	sda-is-open-drain;
> +	scl-is-open-drain;
> +	scl-is-output-only;
> +	speed-hz = <250000>;
> +
> +	audio-video-encoder {
> +		compatible = "nintendo,wii-ave-rvl";
> +		reg = <70>;
> +	};
> +};
> diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
> index d9aa9a6..6cc5f15 100644
> --- a/drivers/i2c/busses/i2c-gpio.c
> +++ b/drivers/i2c/busses/i2c-gpio.c
> @@ -14,8 +14,14 @@
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  #include <linux/platform_device.h>
> +#include <linux/gpio.h>
> +#include <linux/of_i2c.h>
>  
> -#include <asm/gpio.h>
> +struct i2c_gpio_private_data {
> +	struct i2c_adapter adap;
> +	struct i2c_algo_bit_data bit_data;
> +	struct i2c_gpio_platform_data pdata;
> +};
>  
>  /* Toggle SDA by changing the direction of the pin */
>  static void i2c_gpio_setsda_dir(void *data, int state)
> @@ -78,24 +84,80 @@ static int i2c_gpio_getscl(void *data)
>  	return gpio_get_value(pdata->scl_pin);
>  }
>  
> +#ifdef CONFIG_OF
> +#include <linux/of_gpio.h>

Instead of putting the include here, please add #ifdef CONFIG_OF
protection around the contents of linux/of_gpio.h itself.  I fully
support that change so that includes can remain at the top where they
belong.

> +
> +/* Check if devicetree nodes exist and build platform data */
> +static int i2c_gpio_of_probe(struct platform_device *pdev,
> +			     struct i2c_gpio_platform_data *pdata)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	const __be32 *prop;
> +	int sda_pin, scl_pin;
> +	int len;
> +
> +	if (!np || of_gpio_count(np) < 2)
> +		return -ENXIO;
> +
> +	sda_pin = of_get_gpio_flags(np, 0, NULL);
> +	scl_pin = of_get_gpio_flags(np, 1, NULL);
> +	if (sda_pin < 0 || scl_pin < 0) {
> +		pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
> +		       np->full_name, sda_pin, scl_pin);
> +		return -ENXIO;
> +	}
> +
> +	pdata->sda_pin = sda_pin;
> +	pdata->scl_pin = scl_pin;
> +	prop = of_get_property(np, "sda-is-open-drain", NULL);
> +	if (prop)
> +		pdata->sda_is_open_drain = 1;
> +	prop = of_get_property(np, "scl-is-open-drain", NULL);
> +	if (prop)
> +		pdata->scl_is_open_drain = 1;
> +	prop = of_get_property(np, "scl-is-output-only", NULL);
> +	if (prop)
> +		pdata->scl_is_output_only = 1;
> +	prop = of_get_property(np, "speed-hz", &len);
> +	if (prop && len >= sizeof(__be32))
> +		pdata->udelay = DIV_ROUND_UP(1000000, be32_to_cpup(prop) * 2);
> +	prop = of_get_property(np, "timeout", &len);
> +	if (prop && len >= sizeof(__be32))
> +		pdata->timeout = msecs_to_jiffies(be32_to_cpup(prop));
> +
> +	return 0;
> +}
> +#else
> +static int i2c_gpio_of_probe(struct platform_device *pdev,
> +			     struct i2c_gpio_platform_data *pdata)
> +{
> +	return -ENXIO;
> +}
> +#endif
> +
>  static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  {
> +	struct i2c_gpio_private_data *priv;
>  	struct i2c_gpio_platform_data *pdata;
>  	struct i2c_algo_bit_data *bit_data;
>  	struct i2c_adapter *adap;
>  	int ret;
>  
> -	pdata = pdev->dev.platform_data;
> -	if (!pdata)
> -		return -ENXIO;
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +	adap = &priv->adap;
> +	bit_data = &priv->bit_data;
> +	pdata = &priv->pdata;
>  
> -	ret = -ENOMEM;
> -	adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
> -	if (!adap)
> -		goto err_alloc_adap;
> -	bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
> -	if (!bit_data)
> -		goto err_alloc_bit_data;
> +	if (pdev->dev.platform_data) {
> +		*pdata = *(struct i2c_gpio_platform_data *)
> +			pdev->dev.platform_data;
> +	} else {
> +		ret = i2c_gpio_of_probe(pdev, pdata);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	ret = gpio_request(pdata->sda_pin, "sda");
>  	if (ret)
> @@ -143,6 +205,7 @@ static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  	adap->algo_data = bit_data;
>  	adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
>  	adap->dev.parent = &pdev->dev;
> +	adap->dev.of_node = pdev->dev.of_node;
>  
>  	/*
>  	 * If "dev->id" is negative we consider it as zero.
> @@ -154,13 +217,16 @@ static int __devinit i2c_gpio_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_add_bus;
>  
> -	platform_set_drvdata(pdev, adap);
> +	platform_set_drvdata(pdev, priv);
>  
>  	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
>  		 pdata->sda_pin, pdata->scl_pin,
>  		 pdata->scl_is_output_only
>  		 ? ", no clock stretching" : "");
>  
> +	/* Now register all the child nodes */
> +	of_i2c_register_devices(adap);
> +
>  	return 0;
>  
>  err_add_bus:
> @@ -168,34 +234,41 @@ err_add_bus:
>  err_request_scl:
>  	gpio_free(pdata->sda_pin);
>  err_request_sda:
> -	kfree(bit_data);
> -err_alloc_bit_data:
> -	kfree(adap);
> -err_alloc_adap:
>  	return ret;
>  }
>  
>  static int __devexit i2c_gpio_remove(struct platform_device *pdev)
>  {
> +	struct i2c_gpio_private_data *priv;
>  	struct i2c_gpio_platform_data *pdata;
>  	struct i2c_adapter *adap;
>  
> -	adap = platform_get_drvdata(pdev);
> -	pdata = pdev->dev.platform_data;
> +	priv = platform_get_drvdata(pdev);
> +	adap = &priv->adap;
> +	pdata = &priv->pdata;
>  
>  	i2c_del_adapter(adap);
>  	gpio_free(pdata->scl_pin);
>  	gpio_free(pdata->sda_pin);
> -	kfree(adap->algo_data);
> -	kfree(adap);
>  
>  	return 0;
>  }
>  
> +#ifdef CONFIG_OF
> +static const struct of_device_id i2c_gpio_match[] = {
> +	{ .compatible = "i2c-gpio", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, i2c_gpio_match);
> +#else /* CONFIG_OF */
> +#define i2c_gpio_match NULL
> +#endif /* CONFIG_OF */
> +
>  static struct platform_driver i2c_gpio_driver = {
>  	.driver		= {
>  		.name	= "i2c-gpio",
>  		.owner	= THIS_MODULE,
> +		.of_match_table = i2c_gpio_match,
>  	},
>  	.probe		= i2c_gpio_probe,
>  	.remove		= __devexit_p(i2c_gpio_remove),
> -- 
> 1.7.4
> 
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