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 <[email protected]> --- 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@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@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 _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
