[coreboot] Patch: support for the Lenovo Thinkpad W520

[Nico Huber]

Hi,

On 06.11.2016 11:25, Patrick Rudolph wrote:
> Am 06.11.2016 um 09:33 schrieb Charlotte Plusplus:
>> Also, in romstage I am not sure of :
>>          /* Disable unused devices (board specific) */
>>          RCBA32(FD) = 0x1ee51fe3;
> You can dump the value stock lenovo bios sets at boot using the
> inteltool, that ships in coreboot's utils folder.
>>
>> The W520 is a bit different from a t420 and I think it may not be the
>> same. How do I compute this number?

The function disable (FD) register is publicly documented [1, p.407].
As most times, the documentation isn't comprehensive. There are some
more bits explained in src/southbridge/intel/bd82x6x/pch.h:442, bit 27
is for the xHCI controller, bit 26 should always be set. Bits 5:12 btw.
don't apply to your PCH, they used to be for UHCI controllers. The only
bit in the number above I can't figure out is bit 28.

The FD register is actually configured dynamically based on the device-
tree (see src/southbridge/intel/bd82x6x/pch.c). So you don't need an
ugly constant there. You should only make sure that PCH_DISABLE_ALWAYS
is set. Some boards also disable the PCI bridge early so that this one
doesn't get probed (just an optimization). I'm not sure, why disabling
the bridge in the devicetree wouldn't suffice.

Nico

[1]
http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/6-chipset-c200-chipset-datasheet.pdf