[coreboot - Bug #611] I2C Controllers fail to initialize under Win11 with top-down allocation on pre-FSP 2.0 platforms

Issue #611 has been updated by Maximilian Brune.


For EDK2 upstream the RESOURCE_ALLOCATION_TOP_DOWN option is not default on.
I for example (on a recent AMD platform) have a problem in this function: https://github.com/tianocore/edk2/blob/80eaa563ec1cd2272334134d5fd35d856843fe65/UefiPayloadPkg/Library/PciHostBridgeLib/PciHostBridgeSupport.c#L208
It seems to assume all PCIe resources are continuous. And in my case they are not, because from top down the allocations are continuous, but there is a single device that has an allocation further down. And apparently that function just takes the lowest and highest resource and defines that as reserved MMIO space. I got kind of lucky because it asserts, since the ECAM address is directly between that and EDK2 notices it can reserve memory for it.

Maybe you hit a similar issue, but its more obfuscated in your case? In any case we should update the UEFIPayloadPkg function (hoping nothing else in EDK2 depends on it) to not assume a continuous MMIO space. It may also work to use ALWAYS_ALLOW_ABOVE_4G_ALLOCATION=y but I didn't try that yet.

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Bug #611: I2C Controllers fail to initialize under Win11 with top-down allocation on pre-FSP 2.0 platforms
https://ticket.coreboot.org/issues/611#change-2151

* Author: Matt DeVillier
* Status: New
* Priority: Normal
* Category: coreboot common code
* Target version: none
* Start date: 2025-10-12
* Affected versions: main
----------------------------------------
When booting Win11 using edk2 payload and top-down resource allocation (which is now the default), pre-FSP 2.0 platforms all seem to have issues with the I2C controllers failing to initialize.

Windows Device Manager reports a Code 35 error:
Your computer's system firmware does not include enough information to properly configure and use this device. To use this device, contact your computer manufacturer to obtain a firmware or BIOS update.

Microsoft's support pages provide the following:

> Full Error Message
> 
> Your computer's system firmware does not include enough information to properly configure and use this device. To use this device, contact your computer manufacturer to obtain a firmware or BIOS update. (Code 35)
> 
> Cause
> 
> The Multiprocessor System (MPS) table, which stores the resource assignments for the BIOS, is missing an entry for your device and must be updated.
> 
> Recommended Resolution
> 
> Contact the manufacturer of your computer to update the BIOS. 

compiling with `RESOURCE_ALLOCATION_TOP_DOWN=n` resolves the issue

Tested on:
google/slippy (HSW)
google/auron (BSW)
google/rambi (BYT)
google/cyan (BSW)




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