Reading back the remapped HDP flush register seems to cause
problems on some platforms. All we need is a read, so read back
the memcfg register.
Fixes: c9b8dcabb52a ("drm/amdgpu/hdp4.0: do a posting read when flushing HDP")
Reported-by: Alexey Klimov <alexey.kli...@linaro.org>
Link: https://lists.freedesktop.org/archives/amd-gfx/2025-April/123150.html
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4119
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3908
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
---
drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c
b/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c
index f1dc13b3ab38e..cbbeadeb53f72 100644
--- a/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c
@@ -41,7 +41,12 @@ static void hdp_v4_0_flush_hdp(struct amdgpu_device *adev,
{
if (!ring || !ring->funcs->emit_wreg) {
WREG32((adev->rmmio_remap.reg_offset +
KFD_MMIO_REMAP_HDP_MEM_FLUSH_CNTL) >> 2, 0);
- RREG32((adev->rmmio_remap.reg_offset +
KFD_MMIO_REMAP_HDP_MEM_FLUSH_CNTL) >> 2);
+ /* We just need to read back a register to post the write.
+ * Reading back the remapped register causes problems on
+ * some platforms so just read back the memory size register.
+ */
+ if (adev->nbio.funcs->get_memsize)
+ adev->nbio.funcs->get_memsize(adev);
} else {
amdgpu_ring_emit_wreg(ring, (adev->rmmio_remap.reg_offset +
KFD_MMIO_REMAP_HDP_MEM_FLUSH_CNTL) >> 2, 0);
}
--
2.49.0
