[coreboot] alix2c3 LEDs and mode switch

[Roman Yeryomin]

Is there any chance to get LEDs working on alix boards?
I suppose only GPIO lines/ports should be enabled in coreboot an
everything else is done in software.
Here is what documentation says about them:

Status LEDs are all turned on by the BIOS on power up. The BIOS will
turn off LEDs 2 and 3
before booting the operating system.
Location              GPIO           read port                write port
LED1 (left)           G6             port 06100h bit 6        port
06100h bit 6 / 22
LED2 (middle)         G25            port 06180h bit 9        port
06180h bit 9 / 25
LED3 (right)          G27            port 06180h bit 11       port
06180h bit 11 / 27
The CS5536 GPIO ports are programmed by 32 bit atomic writes. This
avoids the need for read /
modify / write operations and the locking issues they entail. For
example, to turn off LED1 (high),
write 0000'0040h to port 06100h. To turn on LED1 (low), write
0040'0000h. Multiple port bits can
be changed at the same time.


Maybe mode switch could also be useful:

The mode switch can be accessed by software as follows:
Location              GPIO           read port
MODESW#               G24            port 061b0h bit 8        (active
low, 0 = switch pressed)


Roman