[XS] Change in coreboot[main]: soc/intel/mtl: Set HDA subsystem ID during FSP-M

[Subrata Banik (Code Review)]

Attention is currently required from: Dinesh Gehlot, Eran Mitrani, Jakub Czapiga, Kapil Porwal, Tarun, Tim Crawford.

Subrata Banik has posted comments on this change by Tim Crawford. ( https://review.coreboot.org/c/coreboot/+/82731?usp=email )

Change subject: soc/intel/mtl: Set HDA subsystem ID during FSP-M
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Patch Set 2:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/82731/comment/4f543e2b_46991bda?usp... :
PS2, Line 7:  Set HDA subsystem ID during FSP-M
> We see no SSID reported in `lspci -s 0:1f.3 -vnn` without this change on Clevo L240TU and V5[46]0TU, so I assume it's already locked with a value of 0.
>
> Setting this UPD causes SSID to show up in lspci.

based on our debug during MTL, we  have highlighted what all IPs are being locked post FSP-S hence, this is surprising to me that fill_fsps_pci_ssid_params() unable to resolve your problem (which is still before FSP-S). I don't think FSP locks anything prior to FSP-S execution.  Hence, setting SSID before FSP-M is too early.