On 01.09.25 12:00, Timur Kristóf wrote:
> Technically not necessary, but clear the extra dwords too,
> so that the command processors don't read uninitialized memory.
That is most likely a really bad idea.
The extra DWs are filled with a specific pattern for a HW workaround.
Clearing them to NOPs makes no sense at all and potentially even breaks the HW
workaround.
Regards,
Christian.
>
> Fixes: c8c1a1d2ef04 ("drm/amdgpu: define and add extra dword for jpeg ring")
> Signed-off-by: Timur Kristóf <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> index 7670f5d82b9e..6a55a85744a9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h
> @@ -474,6 +474,11 @@ static inline void amdgpu_ring_clear_ring(struct
> amdgpu_ring *ring)
> while (i <= ring->buf_mask)
> ring->ring[i++] = ring->funcs->nop;
>
> + /* Technically not necessary, but clear the extra dwords too,
> + * so that the command processors don't read uninitialized memory.
> + */
> + for (i = 0; i < ring->funcs->extra_dw; i++)
> + ring->ring[ring->ring_size / 4 + i] = ring->funcs->nop;
> }
>
> static inline void amdgpu_ring_write(struct amdgpu_ring *ring, uint32_t v)
