Re: [PATCH 1/4] i2c/gpio-i2c add: add DT support

[Jean-Christophe PLAGNIOL-VILLARD <plagnioj-sclMFOaUSTBWk0Htik3J/w@public.gmane.org>]

On 19:38 Mon 06 Feb     , Karol Lewandowski wrote:
> On 05.02.2012 11:38, Jean-Christophe PLAGNIOL-VILLARD wrote:
> 
> Hi!
> 
> >+Device-Tree bindings for i2c gpio driver
> >+
> >+Required properties:
> >+	- compatible = "gpio-i2c";
> 
> Driver name is "i2c-gpio" in file i2c-gpio.c. Previous version of
> patch adding DT-support (prepared by Thomas Chou[1]) used i2c-gpio -
> could we stick to that name?
> 
> [1] https://lkml.org/lkml/2011/2/23/584
> 
> >+	- gpios: sda and scl gpio
> >+
> >+
> >+Optional properties:
> >+	- gpio-i2c,sda_is_open_drain: sda as open drain
> >+	- gpio-i2c,scl_is_open_drain: scl as open drain
> >+	- gpio-i2c,scl_is_output_only: scl as output only
> 
> Most of DT-properties I've seen used hyphen, not underscore.  Could
> we stick to that convention?
> 
> (Nitpick: I think that "is" in property names is redundant too.)
> 
> >+	- udelay: half clock cycle time in us (may depend on each platform)
> 
> Could we use "clock-frequency" as Grant have suggested during review
> of previous patch to i2c-gpio?
as exaplained no as for gpio the delay is platform dependent
> 
>   https://lkml.org/lkml/2011/2/24/220
> 
> >+	- timeout: timeout to get data
> >+
> >+
> >+Example nodes:
> >+
> >+i2c-gpio@0 {
> >+	compatible = "gpio-i2c";
> >+	gpios =<&pioA 23 0 /* sda */
> >+		&pioA 24 0 /* scl */
> >+		>;
> >+	gpio-i2c,sda_is_open_drain;
> >+	gpio-i2c,scl_is_open_drain;
> >+	udelay =<2>;		/* ~100 kHz */
> >+	#address-cells =<1>;
> >+	#size-cells =<0>;
> >+
> >+	rv3029c2@56 {
> >+		compatible = "rv3029c2";
> >+		reg =<0x56>;
> >+	};
> >+};
> >diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
> >index a651779..6b5d794 100644
> >--- a/drivers/i2c/busses/i2c-gpio.c
> >+++ b/drivers/i2c/busses/i2c-gpio.c
> >@@ -14,6 +14,8 @@
> >  #include<linux/module.h>
> >  #include<linux/slab.h>
> >  #include<linux/platform_device.h>
> >+#include<linux/of_gpio.h>
> >+#include<linux/of_i2c.h>
> >
> >  #include<asm/gpio.h>
> >
> >@@ -78,16 +80,51 @@ static int i2c_gpio_getscl(void *data)
> >  	return gpio_get_value(pdata->scl_pin);
> >  }
> >
> >+static int of_i2c_gpio_probe(struct device_node *np,
> >+			     struct i2c_gpio_platform_data *pdata)
> >+{
> >+	u32 reg;
> >+
> 
> if (of_gpio_count(np) < 2)
> 	return -EINVAL;
ok
> 
> >+	pdata->sda_pin = of_get_gpio(np, 0);
> >+	pdata->scl_pin = of_get_gpio(np, 1);
> 
> if (pdata->sda_pin < 0 || pdata->scl_pin < 0)
> 	return -EINVAL;

> 
> >+
> >+	if (of_property_read_u32(np, "udelay",&reg))
> >+		pdata->udelay = reg;
> >+
> >+	if (of_property_read_u32(np, "timeout",&reg))
> >+		pdata->timeout = reg;
> >+
> >+	pdata->sda_is_open_drain =
> >+		!!of_get_property(np, "gpio-i2c,sda_is_open_drain", NULL);
> >+	pdata->scl_is_open_drain =
> >+		!!of_get_property(np, "gpio-i2c,scl_is_open_drain", NULL);
> >+	pdata->scl_is_output_only =
> >+		!!of_get_property(np, "gpio-i2c,scl_is_output_only", NULL);
> >+
> >+	return 0;
> >+}
> >+
> >  static int __devinit i2c_gpio_probe(struct platform_device *pdev)
> >  {
> >  	struct i2c_gpio_platform_data *pdata;
> >  	struct i2c_algo_bit_data *bit_data;
> >  	struct i2c_adapter *adap;
> >  	int ret;
> >+	int len = sizeof(struct i2c_gpio_platform_data);
> >
> >-	pdata = pdev->dev.platform_data;
> >+	pdata = kzalloc(len, GFP_KERNEL);
> 
> Could you also take into account Grant's comment about
> private/platform data?
> 
>   https://lkml.org/lkml/2011/2/3/221
> 
> >  	if (!pdata)
> >-		return -ENXIO;
> >+		return -ENOMEM;
> >+
> >+	if (pdev->dev.of_node) {
> >+		of_i2c_gpio_probe(pdev->dev.of_node, pdata);
> 
> Above might fail if configuration is corrupted.
> 
> >+	} else {
> >+		if (!pdev->dev.platform_data) {
> >+			ret = -ENXIO;
> >+			goto err_alloc_adap;
> >+		}
> >+		memcpy(pdata, pdev->dev.platform_data, len);
> >+	}
> >
> >  	ret = -ENOMEM;
> >  	adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
> >@@ -143,6 +180,7 @@ 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.
> >@@ -154,6 +192,8 @@ static int __devinit i2c_gpio_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		goto err_add_bus;
> >
> >+	of_i2c_register_devices(adap);
> >+
> >  	platform_set_drvdata(pdev, adap);
> >
> >  	dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
> >@@ -172,6 +212,7 @@ err_request_sda:
> >  err_alloc_bit_data:
> >  	kfree(adap);
> >  err_alloc_adap:
> >+	kfree(pdata);
> >  	return ret;
> >  }
> >
> >@@ -192,10 +233,20 @@ static int __devexit i2c_gpio_remove(struct platform_device *pdev)
> >  	return 0;
> >  }
> >
> >+#if defined(CONFIG_OF)
> >+static const struct of_device_id gpio_i2c_dt_ids[] = {
> >+	{ .compatible = "gpio-i2c", },
> 
> There seem to be no good reason to make DT-compatible string
> different from driver's name that's already in use:
> 
> >  static struct platform_driver i2c_gpio_driver = {
> >  	.driver		= {
> >  		.name	= "i2c-gpio",
> 
> Regards,
> -- 
> Karol Lewandowski | Samsung Poland R&D Center | Linux/Platform