drm/amdgpu/sdma5.2: Update wptr registers as well as doorbell

From Alex Deucher
9d74e50098492e89f319ac6922db3c2062f69340 in linux-6.6.y/6.6.44
a03ebf116303e5d13ba9a2b65726b106cb1e96f6 in mainline linux

diff --git a/sys/dev/pci/drm/amd/amdgpu/sdma_v5_2.c b/sys/dev/pci/drm/amd/amdgpu/sdma_v5_2.c
index ac3ae21..61afab0 100644 (file)
--- a/sys/dev/pci/drm/amd/amdgpu/sdma_v5_2.c
+++ b/sys/dev/pci/drm/amd/amdgpu/sdma_v5_2.c
@@ -188,6 +188,14 @@ static void sdma_v5_2_ring_set_wptr(struct amdgpu_ring *ring)
                DRM_DEBUG("calling WDOORBELL64(0x%08x, 0x%016llx)\n",
                                ring->doorbell_index, ring->wptr << 2);
                WDOORBELL64(ring->doorbell_index, ring->wptr << 2);
+               /* SDMA seems to miss doorbells sometimes when powergating kicks in.
+                * Updating the wptr directly will wake it. This is only safe because
+                * we disallow gfxoff in begin_use() and then allow it again in end_use().
+                */
+               WREG32(sdma_v5_2_get_reg_offset(adev, ring->me, mmSDMA0_GFX_RB_WPTR),
+                      lower_32_bits(ring->wptr << 2));
+               WREG32(sdma_v5_2_get_reg_offset(adev, ring->me, mmSDMA0_GFX_RB_WPTR_HI),
+                      upper_32_bits(ring->wptr << 2));
        } else {
                DRM_DEBUG("Not using doorbell -- "
                                "mmSDMA%i_GFX_RB_WPTR == 0x%08x "
@@ -1666,6 +1674,10 @@ static void sdma_v5_2_ring_begin_use(struct amdgpu_ring *ring)
         * but it shouldn't hurt for other parts since
         * this GFXOFF will be disallowed anyway when SDMA is
         * active, this just makes it explicit.
+        * sdma_v5_2_ring_set_wptr() takes advantage of this
+        * to update the wptr because sometimes SDMA seems to miss
+        * doorbells when entering PG.  If you remove this, update
+        * sdma_v5_2_ring_set_wptr() as well!
         */
        amdgpu_gfx_off_ctrl(adev, false);
 }