6.6-stable review patch. If anyone has any objections, please let me know.
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From: Alex Deucher alexander.deucher@amd.com
commit f690e3974755a650259a45d71456decc9c96a282 upstream.
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.klimov@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 Reviewed-by: Felix Kuehling felix.kuehling@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com (cherry picked from commit 5c937b4a6050316af37ef214825b6340b5e9e391) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c +++ b/drivers/gpu/drm/amd/amdgpu/hdp_v4_0.c @@ -42,7 +42,12 @@ static void hdp_v4_0_flush_hdp(struct am { 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); }