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Plummer" , Tomeu Vizoso , Eric Anholt , Alyssa Rosenzweig , Robin Murphy , Philipp Zabel , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Collabora Kernel Team , Neil Armstrong Subject: Re: [PATCH v5 09/11] drm/panfrost: Introduce a reset lock Message-ID: References: <20260811-claude-fixes-v5-0-3d692c9e98c2@collabora.com> <20260811-claude-fixes-v5-9-3d692c9e98c2@collabora.com> <20260812114543.17e5c10d@fedora-21.home> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260812114543.17e5c10d@fedora-21.home> X-Zoho-Virus-Status: 1 X-Zoho-AV-Stamp: zmail-av-0.2.10.1.5.2/286.586.17 On 12.08.2026 11:45, Boris Brezillon wrote: > On Tue, 11 Aug 2026 22:42:18 +0100 > Adrián Larumbe wrote: > > > So as to avoid accessing HW register while a reset is ongoing, a read/write > > semaphore that envelopes the reset sequence will help driver entry points > > avoid racing with it. For now, the only such racy entry point is the ioctl > > that returns the current GPU timestmap. > > > > Signed-off-by: Adrián Larumbe > > --- > > drivers/gpu/drm/panfrost/panfrost_device.c | 2 ++ > > drivers/gpu/drm/panfrost/panfrost_device.h | 1 + > > drivers/gpu/drm/panfrost/panfrost_drv.c | 9 ++++++--- > > drivers/gpu/drm/panfrost/panfrost_job.c | 1 + > > 4 files changed, 10 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.c b/drivers/gpu/drm/panfrost/panfrost_device.c > > index 5b66173c75b9..e0390b6c0d22 100644 > > --- a/drivers/gpu/drm/panfrost/panfrost_device.c > > +++ b/drivers/gpu/drm/panfrost/panfrost_device.c > > @@ -602,6 +602,8 @@ bool panfrost_exception_needs_reset(const struct panfrost_device *pfdev, > > > > void panfrost_device_reset(struct panfrost_device *pfdev, bool enable_job_int) > > { > > + guard(rwsem_read)(&pfdev->reset.lock); > > Oops, s/rwsem_read/rwsem_write/. This is actually fixed in the next > patch. Sorry about this, I seemed to have botched the final interactive rebase. > > + > > panfrost_gpu_soft_reset(pfdev); > > panfrost_gpu_power_on(pfdev); > > panfrost_mmu_reset(pfdev); > > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h > > index 4bbaaaf827a5..a2a68e042225 100644 > > --- a/drivers/gpu/drm/panfrost/panfrost_device.h > > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h > > @@ -166,6 +166,7 @@ struct panfrost_device { > > struct { > > struct workqueue_struct *wq; > > struct work_struct work; > > + struct rw_semaphore lock; > > atomic_t pending; > > } reset; > > > > diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c > > index 958f1d36ab10..ff23b1a979bb 100644 > > --- a/drivers/gpu/drm/panfrost/panfrost_drv.c > > +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c > > @@ -41,9 +41,12 @@ static int panfrost_ioctl_query_timestamp(struct panfrost_device *pfdev, > > if (ret) > > return ret; > > > > - panfrost_cycle_counter_get(pfdev); > > - *arg = panfrost_timestamp_read(pfdev); > > - panfrost_cycle_counter_put(pfdev); > > + /* We should not read timestamp register while the GPU is being reset */ > > + scoped_guard(rwsem_read, &pfdev->reset.lock) { > > + panfrost_cycle_counter_get(pfdev); > > + *arg = panfrost_timestamp_read(pfdev); > > + panfrost_cycle_counter_put(pfdev); > > + } > > > > pm_runtime_put(pfdev->base.dev); > > return 0; > > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c > > index c761379851da..9d7dafa29f19 100644 > > --- a/drivers/gpu/drm/panfrost/panfrost_job.c > > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c > > @@ -874,6 +874,7 @@ int panfrost_jm_init(struct panfrost_device *pfdev) > > > > INIT_WORK(&pfdev->reset.work, panfrost_reset_work); > > spin_lock_init(&js->job_lock); > > + init_rwsem(&pfdev->reset.lock); > > > > js->irq = platform_get_irq_byname(to_platform_device(pfdev->base.dev), "job"); > > if (js->irq < 0) > > Adrian Larumbe