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

On 19:38 Mon 06 Feb     , Karol Lewandowski wrote:

On 05.02.2012 11:38, Jean-Christophe PLAGNIOL-VILLARD wrote:

Hi!

quoted

+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

quoted

+	- 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.)

quoted

+	- 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

quoted

+	- 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

quoted

+	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;

quoted

+
+	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

quoted

 	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.

quoted

+	} 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:

quoted

 static struct platform_driver i2c_gpio_driver = {
 	.driver		= {
 		.name	= "i2c-gpio",

Regards,
-- 
Karol Lewandowski | Samsung Poland R&D Center | Linux/Platform