Hi Grant,
I did some work on the gpio and pinmux device tree support for exynos.
I thought to discuss with you about what was done before proceeding
further.
In the dts file, the interrupt controller node is listed as
GPA: gpio-controller@11400000 {
compatible = "samsung,exynos4-gpio-gpa0",
"samsung,exynos4-gpio";
#gpio-cells = <4>;
gpio-controller;
};
The meaning of the 4 cells are as below. The values of all the cells
are set as per the exynos chip specification.
< [GPIO Pin Number] [Pin-Mux Function Number] [Pull Up/Down Setting]
[Driver Strength Setting] >
Device nodes would include the gpio's that it would use (as in below example)
serial@13800000 {
compatible = "samsung,s5pv310-uart";
reg = <0x13800000 0x100>;
interrupts = <116>;
gpios = <&GPA 0 2 0 2 /* Tx */
&GPA 1 2 0 2>; /* Rx */
};
When the gpio_chip is registered, the corresponding node is searched
in the device tree and attached to the gpio_chip. Along with node
pointer, the of_gpio_n_cells is set to 4 and the of_xlate function is
set to point to the function listed below.
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;
/* Set PinMux */
s3c_gpio_cfgpin(pin, be32_to_cpu(gpio[1]));
/* Set pull up/down */
s3c_gpio_setpull(pin, be32_to_cpu(gpio[2]));
/* Set driver strength */
s5p_gpio_set_drvstr(pin, be32_to_cpu(gpio[3]));
return n;
}
The above function translates the gpio controller pin number to a
linux gpio number and sets the pinmux, pull up/down and driver
strength values. The device driver uses the of_get_gpio() function to
get the gpio pin number and then calls gpio_request on that gpio
number. The call to of_get_gpio() invokes the gpio translate function
which sets the pinmux, pull up/down and driver strength values.
This handles the gpio and pinmux requirements for exynos. Would this
approach be acceptable?
Thanks,
Thomas.
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