Re: [PATCH v3 3/3] drm/amdgpu: reset VI ASIC on Apple boards with VRAM at 0

["Francisco Beltrán Millalén" <fbeltranmillalen@gmail.com>]

Hi Maciej,

Thanks for the patch.

I applied patch 3 to the 6.18.49 kernel I use on my MacBookPro14,3
(Radeon Pro 555, 1002:67ef, subsystem 106b:017a, rev c7).  The kernel
also carries my unrelated PCI and ACPI patches for this machine.

After a cold boot, amdgpu logs "PCI CONFIG reset" and "GPU posting
now..." while it loads, and VRAM ends up at 0xF400000000.
MC_VM_FB_LOCATION reads 0xf47ff400 through debugfs.  In my tests in
September, a kernel without the reset left VRAM at 0 after a cold boot.

I then suspended to RAM three times with rtcwake.  After each resume
MC_VM_FB_LOCATION was still 0xf47ff400, the screen came back, and the
kernel log showed no VM faults, ring timeouts or GPU recovery.  After
the last one I ran glxgears for a minute and the gfx ring kept going.

I also closed the lid for about ten minutes.  After opening it the
screen came back, MC_VM_FB_LOCATION was 0xf47ff400, and glxgears ran
for a minute without errors.

Before that I had also tried it after a warm reboot, with four rtcwake
cycles and one 45-minute suspend from the idle timer.  After each of
those MC_VM_FB_LOCATION was 0xf47ff400 and the log showed no GPU
errors.

Finally, I reloaded amdgpu after a suspend, twice, with modprobe -r
and modprobe.  Each time amdgpu logged "PCI CONFIG reset" and "GPU
posting now..." during the reload, VRAM was at 0xF400000000 and
MC_VM_FB_LOCATION read 0xf47ff400.  VRAM is no longer at 0 by then, so
I think the reset came from the existing SMC check: with amdgpu
unloaded, SMC_SYSCON_CLOCK_CNTL_0 read 0x01000000 and SMC_PC_C was
about 0x205xx and changing (read through the MMIO BAR).  After the
second reload I logged in again and ran glxgears for a minute without
errors.

Tested-by: Francisco Beltrán Millalén <fbeltranmillalen@gmail.com> # MacBookPro14,3

Thanks again,
Francisco