[PATCH 05/14] ARM: at91: add pinctrl support

[Stephen Warren]

On 08/23/2012 01:06 AM, Richard Genoud wrote:
> 2012/8/22 Stephen Warren <swarren at wwwdotorg.org>:
>>>> +Required properties for iomux controller:
>>>> +- compatible: "atmel,at91rm9200-pinctrl"
>>>> +- atmel,mux-mask: array of mask (periph per bank) to describe if a pin can be
>>>> +  configured in this periph mode. All the periph and bank need to be describe.
>>>
>>> Can you please be more elaborate on this mux-mask, like what each bit
>>> means and why the bits are arranged like that and what it means on the
>>> AT91 platform.... I was first reading the .dts and was like ?woot? so
>>> I go to the bindings doc and I read this and I'm still like ?woot?..
>>
>> Yes, I'm a little confused what this is, and wouldn't have a clue how to
>> fill it in.
>
> With a practical example it's easier to understand.
> Take a SAM9X5 release manual (here is sam9g35):
> http://www.atmel.com/Images/doc11053.pdf page 11 (§4.3 package pinout)
> in the file arch/arm/boot/dts/at91sam9x5.dtsi you've got the the
> atmel,mux-mask like that:
>
> /* periphA  periphB    periphC     */
> 0xffffffff 0xffe0399f 0xc000001c  /* pioA */
> 0x0007ffff 0x8000fe3f 0x00000000  /* pioB */
> 0x80000000 0x07c0ffff 0xb83fffff  /* pioC */
> 0x003fffff 0x003f8000 0x00000000  /* pioD */
> 
> Let's take the PioA - peripheral B: 0xffe0399f
> From the documentation table 4-3, we can extract the column PIO
> Periperal B for all signals PA0-PA31:
...
> Each time it's possible to mux a pin to the peripheral B function (ie
> when there's no "-----") the corresponding bit is set:
...
> => this gives 0x399f

Ah OK. It would be a good idea to briefly describe this process in the
binding document I think. I assume this property exists to avoid the
kernel driver having to contain tables for each Atmel device; the driver
is generic.