Furquan Shaikh has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/41155 )
Change subject: soc/intel/common/block/systemagent: Use TOUUD as base for MMIO above 4G ......................................................................
Patch Set 2:
(1 comment)
https://review.coreboot.org/c/coreboot/+/41155/2/src/soc/intel/common/block/... File src/soc/intel/common/block/systemagent/systemagent.c:
https://review.coreboot.org/c/coreboot/+/41155/2/src/soc/intel/common/block/... PS2, Line 118: if (!get_enable_above_4GB_mmio())
Why wouldn't we always report the usable address space above 4GiB? It seems odd to have this option. […]
That is what I am trying to track down. I found this CL from Subrata: https://review.coreboot.org/c/coreboot/+/38125, but I don't really understand the commit message "Publishing unnecessary 4GB above MMIO resource with wrong base and size is causing problem while working with discrete GPU."
What do you mean by wrong base and size?
BTW, Intel just reported that they are seeing a different behavior w.r.t. hotplug driver even with USB4 if this patch is used v/s only reporting the allocated MMIO window above 4G. I have asked for more details here: https://b.corp.google.com/issues/149186922#comment37