On 31/07/2025 11:57, Steven Price wrote: > On 30/07/2025 18:43, Karunika Choo wrote: >> In certain scenarios, it is possible for multiple cache flushes to be >> requested before the previous one completes. This patch introduces the >> cache_flush_lock mutex to serialize these operations and ensure that >> any requested cache flushes are completed instead of dropped. >> >> Signed-off-by: Karunika Choo <karunika.c...@arm.com> >> Co-developed-by: Dennis Tsiang <dennis.tsi...@arm.com> > > A Co-Developed-By needs to have a signed-off-by too[1]
Oops. I can push a v2 to add those. > > [1] > https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by > > But I also don't understand how this is happening. The only caller to > panthor_gpu_flush_caches() is in panthor_sched_suspend() and that is > holding the sched->lock mutex. The fix is in relation to the enablement of GPU Flush caches by default for all GPUs [1]. While calls from the MMU are serialized, other calls i.e. from panthor_sched_suspend() are not. As such, this patch explicitly serializes these operations. [1] https://lore.kernel.org/all/20250724124210.3675094-6-karunika.c...@arm.com/ Kind regards, Karunika Choo > Steve > >> --- >> drivers/gpu/drm/panthor/panthor_gpu.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c >> b/drivers/gpu/drm/panthor/panthor_gpu.c >> index cb7a335e07d7..030409371037 100644 >> --- a/drivers/gpu/drm/panthor/panthor_gpu.c >> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c >> @@ -35,6 +35,9 @@ struct panthor_gpu { >> >> /** @reqs_acked: GPU request wait queue. */ >> wait_queue_head_t reqs_acked; >> + >> + /** @cache_flush_lock: Lock to serialize cache flushes */ >> + struct mutex cache_flush_lock; >> }; >> >> /** >> @@ -204,6 +207,7 @@ int panthor_gpu_init(struct panthor_device *ptdev) >> >> spin_lock_init(&gpu->reqs_lock); >> init_waitqueue_head(&gpu->reqs_acked); >> + mutex_init(&gpu->cache_flush_lock); >> ptdev->gpu = gpu; >> panthor_gpu_init_info(ptdev); >> >> @@ -353,6 +357,9 @@ int panthor_gpu_flush_caches(struct panthor_device >> *ptdev, >> bool timedout = false; >> unsigned long flags; >> >> + /* Serialize cache flush operations. */ >> + guard(mutex)(&ptdev->gpu->cache_flush_lock); >> + >> spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags); >> if (!drm_WARN_ON(&ptdev->base, >> ptdev->gpu->pending_reqs & >> GPU_IRQ_CLEAN_CACHES_COMPLETED)) { >
