From 09a67694edd1f787c206cd2fd066b0ca37debe9f Mon Sep 17 00:00:00 2001
From: Alex Deucher <alexander.deucher@amd.com>
Date: Tue, 9 Jul 2024 17:54:11 -0400
Subject: [PATCH] drm/amdgpu/sdma5.2: Update wptr registers as well as doorbell
commit a03ebf116303e5d13ba9a2b65726b106cb1e96f6 upstream.
We seem to have a case where SDMA will sometimes miss a doorbell
if GFX is entering the powergating state when the doorbell comes in.
To workaround this, we can update the wptr via MMIO, however,
this is only safe because we disallow gfxoff in begin_ring() for
SDMA 5.2 and then allow it again in end_ring().
Enable this workaround while we are root causing the issue with
the HW team.
Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/3440
Tested-by: Friedrich Vock <friedrich.vock@gmx.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
(cherry picked from commit f2ac52634963fc38e4935e11077b6f7854e5d700)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
index cc9e961f0078..af1e90159ce3 100644
--- a/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
+++ b/drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c
@@ -176,6 +176,14 @@ 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 "
@@ -1647,6 +1655,10 @@ 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);
}