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 <thomas.abraham@xxxxxxxxxx>
---
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
--
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