Attention is currently required from: Ethan Tsao, Ravishankar Sarawadi, Tim Wawrzynczak, Paul Menzel, Raj Astekar, Patrick Rudolph. Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/61389 )
Change subject: soc/intel/graphics: Create Kconfig for mapping graphic memory base ......................................................................
Patch Set 19:
(2 comments)
File src/soc/intel/common/block/graphics/Kconfig:
https://review.coreboot.org/c/coreboot/+/61389/comment/8ec6f97c_88f16a58 PS19, Line 26: to : reach at DSM Unless the hardware changed significantly, it's up to the graphics driver if this points to DSM or not. Also, at what offset.
It would really be nice if somebody finds documentation about what changed actually. graphics_get_memory_base() is not even supposed to point to DSM. It's just the base of the logical graphics memory aperture. If the latter is at an offset in future hardware, I can't tell. So the question boils down to: Did the whole aperture move or did the mapping of the framebuffer inside the aperture move (when using the FSP-integrated GOP)?
If it's just the framebuffer allocation that moved when using the FSP-integrated GOP driver, that should be handled in the caller of graphics_get_memory_base() and not inside the latter. Also, in case it's about the framebuffer, a proper implementation should use EFI_PEI_GRAPHICS_INFO_HOB and not try to guess things from register values. However, FSP spec notes that the value may need to be updated in case the BAR moves (e.g. via coreboot's allocator). Um, might be easier to not use the FSP/GOP in the first place ;)
https://review.coreboot.org/c/coreboot/+/61389/comment/5c34baf8_58c3e08e PS19, Line 29: GTT_SIZE
So if I understand correctly, really, all this is saying is that the framebuffer that the GFX PEIM c […]
DSM used to mean the space of system DRAM that is pre-allocated for graphics, aka. graphics stolen memory. It's where any pre-OS driver usually sets up the framebuffer. Unless they completely changed the hardware, the space behind BAR2 is just logical graphics memory and can point to anything via page tables (gGTT), so it seems likely we are dealing with a software and not a hardware change here.