On Tuesday, 11 August 2026 16:29:34 Central European Summer Time Boris
Brezillon wrote:
> On Tue, 11 Aug 2026 16:08:31 +0200
> Nicolas Frattaroli <[email protected]> wrote:
>
> > Add two new event tracepoints: gpu_cache_flush_start to be emitted after
> > acquiring the flush mutex and reqs spinlock, and gpu_cache_flush_end to
> > be emitted when leaving the function.
> >
> > This allows debugging the duration a flush takes irrespective of initial
> > function entry lock contention by subtracting the start tracepoint's
> > timestamp from the end tracepoint timestamp, and additionally contains
> > information such as which caches were flushed.
> >
> > Reviewed-by: Steven Rostedt <[email protected]>
> > Reviewed-by: Liviu Dudau <[email protected]>
> > Reviewed-by: Steven Price <[email protected]>
> > Signed-off-by: Nicolas Frattaroli <[email protected]>
> > ---
> > drivers/gpu/drm/panthor/panthor_gpu.c | 7 ++++-
> > drivers/gpu/drm/panthor/panthor_trace.h | 49
> > +++++++++++++++++++++++++++++++++
> > 2 files changed, 55 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c
> > b/drivers/gpu/drm/panthor/panthor_gpu.c
> > index c013d6bf9a59..68e2dd2527df 100644
> > --- a/drivers/gpu/drm/panthor/panthor_gpu.c
> > +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
> > @@ -337,6 +337,7 @@ int panthor_gpu_flush_caches(struct panthor_device
> > *ptdev,
> > guard(mutex)(&ptdev->gpu->cache_flush_lock);
> >
> > spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags);
> > + trace_gpu_cache_flush_start(ptdev->base.dev, l2, lsc, other);
> > if (!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED)) {
> > ptdev->gpu->pending_reqs |= GPU_IRQ_CLEAN_CACHES_COMPLETED;
> > gpu_write(gpu->iomem, GPU_CMD, GPU_FLUSH_CACHES(l2, lsc,
> > other));
> > @@ -345,8 +346,10 @@ int panthor_gpu_flush_caches(struct panthor_device
> > *ptdev,
> > }
> > spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
> >
> > - if (ret)
> > + if (ret) {
> > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other);
>
> I don't mind having start/end traces, but I still think it'd be
> valuable to report failure cases.
Alright, I think in that case I will get rid of the start/end ones
(since they now need to have different args) and just do one on exit
with a duration arg and an ret arg.
>
> > return ret;
> > + }
> >
> > if (!wait_event_timeout(ptdev->gpu->reqs_acked,
> > !(ptdev->gpu->pending_reqs &
> > GPU_IRQ_CLEAN_CACHES_COMPLETED),
> > @@ -360,6 +363,8 @@ int panthor_gpu_flush_caches(struct panthor_device
> > *ptdev,
> > spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags);
> > }
> >
> > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other);
> > +
> > if (ret) {
> > panthor_device_schedule_reset(ptdev);
> > drm_err(&ptdev->base, "Flush caches timeout");
> > diff --git a/drivers/gpu/drm/panthor/panthor_trace.h
> > b/drivers/gpu/drm/panthor/panthor_trace.h
> > index 6ffeb4fe6599..6951b95b1de7 100644
> > --- a/drivers/gpu/drm/panthor/panthor_trace.h
> > +++ b/drivers/gpu/drm/panthor/panthor_trace.h
> > @@ -76,6 +76,55 @@ TRACE_EVENT(gpu_job_irq,
> > __entry->events, __entry->duration_ns)
> > );
> >
> > +DECLARE_EVENT_CLASS(gpu_cache_flush_template,
> > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other),
> > + TP_ARGS(dev, l2, lsc, other),
> > + TP_STRUCT__entry(
> > + __string(dev_name, dev_name(dev))
> > + __field(u32, l2)
> > + __field(u32, lsc)
> > + __field(u32, other)
> > + ),
> > + TP_fast_assign(
> > + __assign_str(dev_name);
> > + __entry->l2 = l2;
> > + __entry->lsc = lsc;
> > + __entry->other = other;
> > + ),
> > + TP_printk("%s: l2=0x%x lsc=0x%x other=0x%x", __get_str(dev_name),
> > + __entry->l2, __entry->lsc, __entry->other)
> > +);
> > +
> > +/**
> > + * gpu_cache_flush_start - called after cache flush locks taken, before
> > flush
> > + * @dev: pointer to the &struct device, for printing the device name
> > + * @l2: "l2" flush flags
> > + * @lsc: "lsc" flush flags
> > + * @other: "other" flush flags
> > + *
> > + * Fires after any initial lock contention around the locks needed for
> > flushing
> > + * caches, but before the actual cache flush is requested.
> > + */
> > +DEFINE_EVENT(gpu_cache_flush_template, gpu_cache_flush_start,
> > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other),
> > + TP_ARGS(dev, l2, lsc, other)
> > +);
> > +
> > +/**
> > + * gpu_cache_flush_end - called after cache flush
> > + * @dev: pointer to the &struct device, for printing the device name
> > + * @l2: "l2" flush flags
> > + * @lsc: "lsc" flush flags
> > + * @other: "other" flush flags
> > + *
> > + * Fires after either the cache flush is complete, or has failed. Can be
> > used
> > + * together with gpu_cache_flush_start to get how long the flush has taken.
> > + */
> > +DEFINE_EVENT(gpu_cache_flush_template, gpu_cache_flush_end,
> > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other),
> > + TP_ARGS(dev, l2, lsc, other)
> > +);
> > +
> > #endif /* __PANTHOR_TRACE_H__ */
> >
> > #undef TRACE_INCLUDE_PATH
> >
>
>
