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h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:MIME-Version:Content-Transfer-Encoding:Content-Type:Message-Id:Reply-To; bh=+QCoBQ/nMimMy4LMAtD5yKqqd8+uHbcNIS741qDtdC4=; b=Jg9UFV2+f7BsLxGWnKlDOAZoqbwNaDv0K+fcryGm3TBIm4LJfh/ZC0ff7sYlvweU JlGyKiNvB/jtyh2ZO6+qbsI1UqDRMIkmdJ5eSbxEtrATIFWl8Kymth/cM3Z9xzHBV55 U2aJIKPFP2nfgtoJf1YcotA8EYPIyTxAGrn08WGg= Received: by mx.zohomail.com with SMTPS id 1785854688105736.3302339094037; Tue, 4 Aug 2026 07:44:48 -0700 (PDT) From: Nicolas Frattaroli To: Boris Brezillon Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Steven Price , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Grant Likely , Heiko Stuebner , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, kernel@collabora.com Subject: Re: [PATCH v2 3/3] drm/panthor: Add tracepoints for cache flushing Date: Tue, 04 Aug 2026 16:44:40 +0200 Message-ID: In-Reply-To: <20260803110358.31afad0b@fedora1.home> References: <20260730-panthor-cache-flush-fix-v2-0-28790478bfff@collabora.com> <20260730-panthor-cache-flush-fix-v2-3-28790478bfff@collabora.com> <20260803110358.31afad0b@fedora1.home> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Monday, 3 August 2026 11:03:58 Central European Summer Time Boris Brezillon wrote: > On Thu, 30 Jul 2026 13:45:16 +0200 > Nicolas Frattaroli 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. > > > > Signed-off-by: Nicolas Frattaroli > > --- > > drivers/gpu/drm/panthor/panthor_gpu.c | 3 ++ > > drivers/gpu/drm/panthor/panthor_trace.h | 49 +++++++++++++++++++++++++++++++++ > > 2 files changed, 52 insertions(+) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c > > index f015bde80abf..a25955ad668b 100644 > > --- a/drivers/gpu/drm/panthor/panthor_gpu.c > > +++ b/drivers/gpu/drm/panthor/panthor_gpu.c > > @@ -336,6 +336,7 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > > guard(mutex)(&ptdev->gpu->cache_flush_lock); > > > > spin_lock(&ptdev->gpu->reqs_lock); > > + 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)); > > @@ -345,6 +346,7 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > > > > if (ret) { > > spin_unlock(&ptdev->gpu->reqs_lock); > > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other); > > Should we add a status to the end event, so that faulty flushes can > be filtered out (those can be immediate, or timeout=100ms depending on > where the failure happens, but they are not reflecting anything useful, > and would pollute the stats)? Actually, if what we care about is the > time it takes to do a flush, do we even need those start/end events, > can't we pass the time as an argument and do the math in the function > like we do in the job IRQ handler? The start/end pattern seems more common across the kernel. Since there is no doubt as to which start correlates with which end due to the mutex, I chose to go with that. > > > return ret; > > } > > > > @@ -358,6 +360,7 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > > ptdev->gpu->pending_reqs &= ~GPU_IRQ_CLEAN_CACHES_COMPLETED; > > } > > spin_unlock(&ptdev->gpu->reqs_lock); > > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other); > > > > if (ret) { > > panthor_device_schedule_reset(ptdev); > > 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 > > > >