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

[Richard Genoud]

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:
     PIO Peripheral B
PA0  SPI1_NPCS1
PA1  SPI1_NPCS2
PA2  MCI1_DA1
PA3  MCI1_DA2
PA4  MCI1_DA3
PA5  --------
PA6  --------
PA7  SPI0_NPCS1
PA8  SPI1_NPCS0
PA9  --------
PA10 --------
PA11 MCI1_DA0
PA12 MCI1_CDA
PA13 MCI1_CK
PA14 --------
PA15 --------
etc...
Each time it's possible to mux a pin to the peripheral B function (ie
when there's no "-----") the corresponding bit is set:
     PIO Peripheral B
PA0  SPI1_NPCS1   1
PA1  SPI1_NPCS2   1
PA2  MCI1_DA1     1
PA3  MCI1_DA2     1

PA4  MCI1_DA3     1
PA5  --------     0
PA6  --------     0
PA7  SPI0_NPCS1   1

PA8  SPI1_NPCS0   1
PA9  --------     0
PA10 --------     0
PA11 MCI1_DA0     1

PA12 MCI1_CDA     1
PA13 MCI1_CK      1
PA14 --------     0
PA15 --------     0

=> this gives 0x399f



Best regards,
Richard