drm/amdkfd: align SDMA doorbell base for shader doorbell writes

On GC 9.4.3, 9.4.4 and 9.5.0, doorbell writes issued from shaders are
routed to an SDMA engine at 32-byte (4 doorbell index) granularity.
SDMA engine doorbell ranges are 10 indices apart, so the range of every
odd engine starts 2 indices into a 4-index block that begins in the
previous engine's range. A shader ringing the doorbell of a queue on an
odd engine therefore rings the previous engine instead. The intended
queue never sees the doorbell, so its work stalls and the application
hangs.

Align the per-engine doorbell base up to a 4-index boundary on these
ASICs. Each engine only uses 4 of its 10 indices, so the aligned base
plus the queue offset stays within the engine's range. Even engines are
already aligned, so only the doorbell IDs of odd-engine queues change.

Only doorbells rung by the device itself are routed this way. Doorbell
writes from the host, including the kernel's own SDMA rings, are not
affected.

The doorbell ID of an SDMA queue is saved in CRIU checkpoints and
checked again on restore. A checkpoint taken before this change that
contains an SDMA queue on an odd engine will fail to restore with
-EINVAL. This is intentional: the restored process still holds the old
doorbell address, so accepting the stale ID would bring back the same
stall.

Tested on MI300X with a shader-rung SDMA doorbell test: queues on odd
engines hung before this change and complete with it.

v2: use u32 instead of uint32_t for the new locals (checkpatch)
v3: name the routing granularity, use dev->node_id, document the
    layout invariants, describe impact
v4: express the granularity in doorbell indices, drop unrelated
    cleanups, explain the CRIU restore behavior, add test note

Fixes: 6df442a03d1a ("drm/amdgpu: add new doorbell assignment table for aqua_vanjaram")
Signed-off-by: Saleel Kudchadker <Saleel.Kudchadker@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ee1379e6d7da47bdf7a8d5b89c2d1b28473701fb)
Cc: stable@vger.kernel.org

0 files changed, 0 insertions, 0 deletions