Change in ...coreboot[master]: mb/asrock/h110m: Unselect incorrect Kconfig symbol

[Angel Pons (Code Review)]

Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/33439 )

Change subject: mb/asrock/h110m: Unselect incorrect Kconfig symbol
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Patch Set 1:
> Patch Set 1: Code-Review-1
>
> this changes behaviour in src/superio/nuvoton/common/early_serial.c:67

The behavior change is intended. It does not make sense for the NCT6791D.

On both the NCT6776 and the NCT6791:
 - The global configuration register 0x2A defaults to 0xC0.
 - Pins 29-36 are muxed COMA/GPIO8: 0 = COMA; 1 = GPIO8.

On the NCT6776:
 - CR 0x2A bit7 muxes pins 29-36.

On the NCT6791:
 - CR 0x2A bit7 muxes pin 29.
 - CR 0x2A bit6 muxes pins 30-36.

The relevant code fragment on nuvoton/common/early_serial.c:

if (CONFIG(SUPERIO_NUVOTON_NCT6776_COM_A))
                /* Route GPIO8 pin group to COM A */
                pnp_write_config(dev, 0x2a, 0x40);

AFAIUI, this is writing the value 0x40 to the global register 0x2A, which sets bit7=0 and bit6=1.

For the NCT6776, this selects the COMA function on all the COMA pins.

For the NCT6791, this selects the COMA function on pin 29, and selects the GPIO8 function on pins 30-36.

Guess what happens to serial.