AMD graphics performance regression in 4.15 and later

[Gabriel C]

2018-04-11 7:02 GMT+02:00 Gabriel C <nix.or.die at gmail.com>:
>>2018-04-11 6:00 GMT+02:00 Gabriel C <nix.or.die at gmail.com>:
>> 2018-04-09 11:42 GMT+02:00 Christian König <ckoenig.leichtzumerken at gmail.com>:
>>> Am 07.04.2018 um 00:00 schrieb Jean-Marc Valin:
> ...
>> I can help testing code for 4.17/++ if you wish but that is *different* storry.
>>
>
> Quick tested an 4.16.0-11490-gb284d4d5a678 , amdgpu and radeon driver
> are broken now in this one.
>
> radeon tells:
>
> ...
>
> [    6.337838] [drm] PCIE GART of 2048M enabled (table at 0x00000000001D6000).
> [    6.338210] radeon 0000:21:00.0: (-12) create WB bo failed
> [    6.338214] radeon 0000:21:00.0: disabling GPU acceleration
>
> ...
>

I have the same Issue now on final 4.17.

Also I played with BIOS options also which does not fix anything but
changes the error message.

IOMMU && SR-IOV disabled the error changes to this :

[    7.092044] [drm:r600_ring_test [radeon]] *ERROR* radeon: ring 0
test failed (scratch(0x850C)=0xCAFEDEAD)
[    7.092059] radeon 0000:21:00.0: disabling GPU acceleration


While I could workaround SWIOTLB bugs in 4.15 and 4.16 , 4.17 seems to
kill the GPU with no way
for me to make it work ( at least I could not find any workaround by now )

BR