drm/amdgpu/mes12: fix dropped dispatches under queue oversubscription

On gfx12, when more queues are ready than there are HQD slots
(oversubscription), MES keeps queues unmapped and maps a queue to an HQD
on demand when its doorbell rings; a queue is only refetched once its
per-queue work_done is cleared.

Historically oversubscription was handled via the aggregated doorbell,
but that is a shared level-wide signal: MES cannot tell which queue rang
and never clears a queue's work_done, so it relies on the coarse
oversubscription timer to rescan. gfx12 therefore drives GFX/compute
through the per-queue unmapped-doorbell path instead (the aggregated
doorbell now only serves SDMA), which can pinpoint the ringing queue and
lets MES stay idle otherwise.

But with unmapped-doorbell mode 1 (basic) a ring only sets a coarse
level-wide ready flag and does not read the per-queue bitmap or clear the
ringing queue's work_done. A queue still marked done from a prior dispatch
is skipped and its new work is never fetched: the completion never
signals, while queue creation succeeds and no dmesg error is reported.

Switch to mode 2 (basic+): MES reads the per-queue CP_UNMAPPED_QUEUE
bitmap, identifies which queue rang, and clears its work_done so it is
rescheduled promptly. This affects every queue MES schedules on gfx12
(KFD and DRM user queues), which share the one MES instance and this
global setting.

Tested on gfx1201: concurrent multi-queue dispatch that intermittently
stalled under mode 1 now passes on both the KFD and DRM userq paths.

v2: update commit message: describe the oversubscription case, why the
    aggregated doorbell is not used for GFX/compute on gfx12, and why
    basic+ (not basic) is required.

Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Shaoyun Liu <shaoyun.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions