[PATCH] gpio: exynos4: Add device tree support
From: Thomas Abraham <hidden>
Date: 2011-09-01 16:01:37
Also in:
linux-devicetree, linux-samsung-soc
Subsystem:
gpio subsystem, the rest · Maintainers:
Linus Walleij, Bartosz Golaszewski, Linus Torvalds
As gpio chips get registered, a device tree node which represents the
gpio chip is searched and attached to it. A translate function is also
provided to convert the gpio specifier into actual platform settings
for pin function selection, pull up/down and drive strength settings.
Signed-off-by: Thomas Abraham <redacted>
---
This patch addes device tree support for exynos4 with minimal changes to
existing code. All the gpio chips that are registered find a corresponding
gpio-controller in the device tree. An example of such a node is:
gpd1: gpio-controller at 114000C0 {
compatible = "samsung,exynos4-gpio-gpd1", "samsung,exynos4-gpio";
#gpio-cells = <4>;
gpio-controller;
};
Four cells are required to describe a gpio and all its properties. The pin
function selection, pull up/down and drive strength settings are considered
the properties of the gpio pin. This fits well with the hardware organization
of gpio, pinmux, pull up/down and drive strength for exynos4.
The format of the gpio specifier is
<[phandle] [gpio_pin] [function] [pull] [drive_strength]>;
- gpio_pin: Pin number within a gpio-controller.
- function: Pinmux function number (as per the SoC spec).
- pull: Pull up/down setting value (as per the SoC spec).
- drive_strength: Pin Driver strength setting (as per the SoC spec).
Example: A i2c device node which uses two gpio lines is listed below.
i2c at 13860000 {
compatible = "samsung,s3c2440-i2c";
reg = <0x13860000 0x100>;
interrupts = <122>;
gpios = <&gpd1 0 2 3 0
&gpd1 1 2 3 0>;
};
A driver or any other portion of the code that is looking up a gpio number
from a device tree node would first get the gpio number using the of_get_gpio()
function. And then use the gpio_request() function on that gpio number.
This approach has been tested with i2c driver for exynos4.
drivers/gpio/gpio-exynos4.c | 53 +++++++++++++++++++++++++++++++++++++++++++
1 files changed, 53 insertions(+), 0 deletions(-)
diff --git a/drivers/gpio/gpio-exynos4.c b/drivers/gpio/gpio-exynos4.c
index d24b337..aa2d9fb 100644
--- a/drivers/gpio/gpio-exynos4.c
+++ b/drivers/gpio/gpio-exynos4.c@@ -13,6 +13,10 @@ #include <linux/irq.h> #include <linux/io.h> #include <linux/gpio.h> +#ifdef CONFIG_OF +#include <linux/of.h> +#include <linux/slab.h> +#endif #include <mach/map.h>
@@ -320,6 +324,52 @@ static struct s3c_gpio_chip exynos4_gpio_part3_4bit[] = { }, }; +#ifdef CONFIG_OF +int exynos4_gpio_xlate(struct gpio_chip *gc, struct device_node *np, + const void *gpio_spec, u32 *flags) +{ + const __be32 *gpio = gpio_spec; + const u32 n = be32_to_cpup(gpio); + unsigned int pin = gc->base + be32_to_cpu(gpio[0]); + + if (gc->of_gpio_n_cells < 4) { + WARN_ON(1); + return -EINVAL; + } + + if (n > gc->ngpio) + return -EINVAL; + + s3c_gpio_cfgpin(pin, S3C_GPIO_SFN(be32_to_cpu(gpio[1]))); + s3c_gpio_setpull(pin, be32_to_cpu(gpio[2])); + s5p_gpio_set_drvstr(pin, be32_to_cpu(gpio[3])); + return n; +} + +static __init void exynos4_gpiolib_attach_ofnode(struct gpio_chip *gc) +{ + const char exynos4_gpio_compat_base[] = "samsung,exynos4-gpio-"; + char *exynos4_gpio_compat; + + exynos4_gpio_compat = kzalloc(strlen(exynos4_gpio_compat_base) + + strlen(gc->label), GFP_KERNEL); + if (!exynos4_gpio_compat) + return; + + strcpy(exynos4_gpio_compat, exynos4_gpio_compat_base); + strcat(exynos4_gpio_compat, gc->label); + gc->of_node = of_find_compatible_node(NULL, NULL, exynos4_gpio_compat); + gc->of_gpio_n_cells = 4; + gc->of_xlate = exynos4_gpio_xlate; + kfree(exynos4_gpio_compat); +} +#else +static __init void exynos4_gpiolib_attach_ofnode(struct gpio_chip *chip) +{ + return; +} +#endif + static __init int exynos4_gpiolib_init(void) { struct s3c_gpio_chip *chip;
@@ -340,6 +390,7 @@ static __init int exynos4_gpiolib_init(void) } if (chip->base == NULL) chip->base = S5P_VA_GPIO1 + (i) * 0x20; + exynos4_gpiolib_attach_ofnode(&chip->chip); } samsung_gpiolib_add_4bit_chips(exynos4_gpio_part1_4bit, nr_chips);
@@ -357,6 +408,7 @@ static __init int exynos4_gpiolib_init(void) } if (chip->base == NULL) chip->base = S5P_VA_GPIO2 + (i) * 0x20; + exynos4_gpiolib_attach_ofnode(&chip->chip); } samsung_gpiolib_add_4bit_chips(exynos4_gpio_part2_4bit, nr_chips);
@@ -374,6 +426,7 @@ static __init int exynos4_gpiolib_init(void) } if (chip->base == NULL) chip->base = S5P_VA_GPIO3 + (i) * 0x20; + exynos4_gpiolib_attach_ofnode(&chip->chip); } samsung_gpiolib_add_4bit_chips(exynos4_gpio_part3_4bit, nr_chips);
--
1.6.6.rc2