On 29/09/2026 04:44, 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.
Typo: s/timestmap/timestamp > > Reviewed-by: Boris Brezillon <[email protected]> > Signed-off-by: Adrián Larumbe <[email protected]> Reviewed-by: Steven Price <[email protected]> > --- > 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 94d2de341838..80d8f6aed090 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_device.c > +++ b/drivers/gpu/drm/panfrost/panfrost_device.c > @@ -481,6 +481,8 @@ bool panfrost_exception_needs_reset(const struct > panfrost_device *pfdev, > > void panfrost_device_reset(struct panfrost_device *pfdev, bool > enable_job_int) > { > + guard(rwsem_write)(&pfdev->reset.lock); > + > panfrost_gpu_soft_reset(pfdev); > > panfrost_gpu_power_on(pfdev); > diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h > b/drivers/gpu/drm/panfrost/panfrost_device.h > index a0b9a2145fc9..63452febb1cf 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_device.h > +++ b/drivers/gpu/drm/panfrost/panfrost_device.h > @@ -165,6 +165,7 @@ 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 f77780c72a1a..571a26b84126 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 ab65786bf63b..4ddf4b722ddf 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_job.c > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c > @@ -877,6 +877,7 @@ int panfrost_jm_init(struct panfrost_device *pfdev) > INIT_WORK(&pfdev->reset.work, panfrost_reset_work); > spin_lock_init(&js->job_lock); > mutex_init(&pfdev->sched_lock); > + init_rwsem(&pfdev->reset.lock); > > js->irq = platform_get_irq_byname(to_platform_device(pfdev->base.dev), > "job"); > if (js->irq < 0) >
