[PATCH AUTOSEL for 4.15 02/78] drm/amdgpu: use polling mem to set SDMA3 wptr for VF

From: Pixel Ding [ Upstream commit 2ffe31deb27579e2f2c9444e01f4d8abf385d145 ] On Tonga VF, there're 2 sources updating wptr registers for sdma3: 1) polling mem and 2) doorbell. When doorbell and polling mem are both enabled on sdma3, there will be collision hit in occasion

[PATCH AUTOSEL for 4.15 02/78] drm/amdgpu: use polling mem to set SDMA3 wptr for VF

From: Pixel Ding [ Upstream commit 2ffe31deb27579e2f2c9444e01f4d8abf385d145 ] On Tonga VF, there're 2 sources updating wptr registers for sdma3: 1) polling mem and 2) doorbell. When doorbell and polling mem are both enabled on sdma3, there will be collision hit in occasion between those two