On Thu, May 2, 2013 at 9:49 AM, Michel Stempin
<[email protected]> wrote:
> Hi,
>
> It looks like the GPIOs are broken since the introduction of DTS for the
> ramips architecture.
>
> In the DTS include file ("target/linux/ramips/dts/rt3050.dtsi" in my case, by
> this is also true for the other ones), only the number of GPIOs for each
> gpio-controller is defined, but not the GPIO base number for each chip. For
> example:
>
> gpio0: gpio@600 {
> compatible = "ralink,rt3052-gpio",
> "ralink,rt2880-gpio";
> reg = <0x600 0x34>;
>
> gpio-controller;
> #gpio-cells = <2>;
>
> ralink,num-gpios = <24>;
> ralink,register-map = [ 00 04 08 0c
> 20 24 28 2c
> 30 34 ];
>
> This part of DTS is handled by the ralink_gpio_probe() function added by the
> "0130-GPIO-MIPS-ralink-adds-ralink-gpio-support.patch" file for the ramips
> architecture, which sets the GPIO base number to -1 to get a
> dynamically-allocated base GPIO number.
>
> This feature was introduced in Linux kernel 2.6.26-rc1
> (<http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/gpio/gpiolib.c?id=8d0aab2f16c4fa170f32e7a74a52cd0122bbafef>),
> but unfortunately, it is not applicable here, since to avoid using any
> numbers that may have been explicitly assigned but not yet registered, this
> dynamic allocation assigns GPIO numbers from the biggest number on down,
> instead of from the smallest on up.
>
> This assignment is performed by function gpiochip_find_base() in the kernel's
> "drivers/gpio/gpiolib.c" file, and as the same patch above defines
> ARCH_NR_GPIOS to 128, this result in a base GPIO number of 128 - 24 = 104
> instead of the expected 0.
>
> Since changing the dynamic GPIO number feature in the kernel is out of
> question as it would break the userspace ABIs
> (<https://patchwork.kernel.org/patch/2084411/>), what is the best option to
> get the GPIOs back working?
>
> My first guess would be to add a "ralink,base-gpio" property for each
> gpio-controller chip to the DTS files for ralink...
>
> Any suggestions?
Your code should not care about the assigned GPIO number.
gpio_ebi_i2stx_0: gpio@13003040 {
#gpio-cells = <2>;
compatible = "nxp,lpc31xx-gpio";
reg = <0x13003040 0x40>;
gpio-controller;
};
gpio_spi: gpio@13003240 {
#gpio-cells = <2>;
compatible = "nxp,lpc31xx-gpio";
reg = <0x13003240 0x40>;
gpio-controller;
};
Spi device that uses the GPIO...
spi@15002000 {
gpios = <&gpio_spi 4 0 /* chip selects */
&gpio_ebi_i2stx_0 3 0>;
s25sl032a@0 {
compatible = "code,s25sl032a";
reg = <0>;
spi-max-frequency = <1000000>;
};
};
then use something like:
gpio = of_get_gpio_flags(pdev->dev.of_node, i, &flags);
or
cs_gpio = of_get_named_gpio(pdev->dev.of_node, "cs-gpios", i);
To attach your gpio.
>
> -Michel
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--
Jon Smirl
[email protected]
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