| Message ID | 20241113154257.1971284-5-boris.brezillon@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/panthor: Be robust against failures in the resume path | expand |
On 13/11/2024 15:42, Boris Brezillon wrote: > When the runtime PM resume callback returns an error, it puts the device > in a state where it can't be resumed anymore. Make sure we can recover > from such transient failures by calling pm_runtime_set_suspended() > explicitly after a pm_runtime_resume_and_get() failure. > > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> > --- > drivers/gpu/drm/panthor/panthor_device.c | 1 + > drivers/gpu/drm/panthor/panthor_device.h | 17 +++++++++++++++++ > drivers/gpu/drm/panthor/panthor_drv.c | 2 +- > drivers/gpu/drm/panthor/panthor_sched.c | 4 ++-- > 4 files changed, 21 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c > index 353f3aabef42..d3276b936141 100644 > --- a/drivers/gpu/drm/panthor/panthor_device.c > +++ b/drivers/gpu/drm/panthor/panthor_device.c > @@ -486,6 +486,7 @@ int panthor_device_resume(struct device *dev) > > err_set_suspended: > atomic_set(&ptdev->pm.state, PANTHOR_DEVICE_PM_STATE_SUSPENDED); > + atomic_set(&ptdev->pm.recovery_needed, 1); > return ret; > } > > diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h > index 0e68f5a70d20..cc74e99e53f9 100644 > --- a/drivers/gpu/drm/panthor/panthor_device.h > +++ b/drivers/gpu/drm/panthor/panthor_device.h > @@ -9,6 +9,7 @@ > #include <linux/atomic.h> > #include <linux/io-pgtable.h> > #include <linux/regulator/consumer.h> > +#include <linux/pm_runtime.h> > #include <linux/sched.h> > #include <linux/spinlock.h> > > @@ -180,6 +181,9 @@ struct panthor_device { > * is suspended. > */ > struct page *dummy_latest_flush; > + > + /** @recovery_needed: True when a resume attempt failed. */ > + atomic_t recovery_needed; > } pm; > > /** @profile_mask: User-set profiling flags for job accounting. */ > @@ -243,6 +247,19 @@ int panthor_device_mmap_io(struct panthor_device *ptdev, > int panthor_device_resume(struct device *dev); > int panthor_device_suspend(struct device *dev); > > +static inline int panthor_device_resume_and_get(struct panthor_device *ptdev) > +{ > + int ret = pm_runtime_resume_and_get(ptdev->base.dev); > + > + /* If the resume failed, we need to clear the runtime_error, which we > + * can done by forcing the RPM state to suspended. > + */ > + if (ret && atomic_cmpxchg(&ptdev->pm.recovery_needed, 1, 0) == 1) I'm unclear what this atomic achieves. At first glance it appears pointless: with this change if panthor_device_resume() fails then recovery_needed is set to 1. So logically if ret != 0 then also recovery_needed == 1. My second thought was is this to avoid races? If multiple threads are calling this then only one will win the cmpxchg and call pm_runtime_set_suspended. But it's not safe - it's quite possible for the first thread to get past the cmpxchg and be suspended before the second thread comes along and reaches the same point - leading to multiple calls to pm_runtime_set_suspended(). So I'm afraid I don't understand this atomic - what am I missing? Thanks, Steve > + pm_runtime_set_suspended(ptdev->base.dev); > + > + return ret; > +} > + > enum drm_panthor_exception_type { > DRM_PANTHOR_EXCEPTION_OK = 0x00, > DRM_PANTHOR_EXCEPTION_TERMINATED = 0x04, > diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c > index 1498c97b4b85..b7a9adc918e3 100644 > --- a/drivers/gpu/drm/panthor/panthor_drv.c > +++ b/drivers/gpu/drm/panthor/panthor_drv.c > @@ -763,7 +763,7 @@ static int panthor_query_timestamp_info(struct panthor_device *ptdev, > { > int ret; > > - ret = pm_runtime_resume_and_get(ptdev->base.dev); > + ret = panthor_device_resume_and_get(ptdev); > if (ret) > return ret; > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 97ed5fe5a191..77b184c3fb0c 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -2364,7 +2364,7 @@ static void tick_work(struct work_struct *work) > if (!drm_dev_enter(&ptdev->base, &cookie)) > return; > > - ret = pm_runtime_resume_and_get(ptdev->base.dev); > + ret = panthor_device_resume_and_get(ptdev); > if (drm_WARN_ON(&ptdev->base, ret)) > goto out_dev_exit; > > @@ -3131,7 +3131,7 @@ queue_run_job(struct drm_sched_job *sched_job) > return dma_fence_get(job->done_fence); > } > > - ret = pm_runtime_resume_and_get(ptdev->base.dev); > + ret = panthor_device_resume_and_get(ptdev); > if (drm_WARN_ON(&ptdev->base, ret)) > return ERR_PTR(ret); >
On Thu, 14 Nov 2024 10:51:01 +0000 Steven Price <steven.price@arm.com> wrote: > On 13/11/2024 15:42, Boris Brezillon wrote: > > When the runtime PM resume callback returns an error, it puts the device > > in a state where it can't be resumed anymore. Make sure we can recover > > from such transient failures by calling pm_runtime_set_suspended() > > explicitly after a pm_runtime_resume_and_get() failure. > > > > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> > > --- > > drivers/gpu/drm/panthor/panthor_device.c | 1 + > > drivers/gpu/drm/panthor/panthor_device.h | 17 +++++++++++++++++ > > drivers/gpu/drm/panthor/panthor_drv.c | 2 +- > > drivers/gpu/drm/panthor/panthor_sched.c | 4 ++-- > > 4 files changed, 21 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c > > index 353f3aabef42..d3276b936141 100644 > > --- a/drivers/gpu/drm/panthor/panthor_device.c > > +++ b/drivers/gpu/drm/panthor/panthor_device.c > > @@ -486,6 +486,7 @@ int panthor_device_resume(struct device *dev) > > > > err_set_suspended: > > atomic_set(&ptdev->pm.state, PANTHOR_DEVICE_PM_STATE_SUSPENDED); > > + atomic_set(&ptdev->pm.recovery_needed, 1); > > return ret; > > } > > > > diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h > > index 0e68f5a70d20..cc74e99e53f9 100644 > > --- a/drivers/gpu/drm/panthor/panthor_device.h > > +++ b/drivers/gpu/drm/panthor/panthor_device.h > > @@ -9,6 +9,7 @@ > > #include <linux/atomic.h> > > #include <linux/io-pgtable.h> > > #include <linux/regulator/consumer.h> > > +#include <linux/pm_runtime.h> > > #include <linux/sched.h> > > #include <linux/spinlock.h> > > > > @@ -180,6 +181,9 @@ struct panthor_device { > > * is suspended. > > */ > > struct page *dummy_latest_flush; > > + > > + /** @recovery_needed: True when a resume attempt failed. */ > > + atomic_t recovery_needed; > > } pm; > > > > /** @profile_mask: User-set profiling flags for job accounting. */ > > @@ -243,6 +247,19 @@ int panthor_device_mmap_io(struct panthor_device *ptdev, > > int panthor_device_resume(struct device *dev); > > int panthor_device_suspend(struct device *dev); > > > > +static inline int panthor_device_resume_and_get(struct panthor_device *ptdev) > > +{ > > + int ret = pm_runtime_resume_and_get(ptdev->base.dev); > > + > > + /* If the resume failed, we need to clear the runtime_error, which we > > + * can done by forcing the RPM state to suspended. > > + */ > > + if (ret && atomic_cmpxchg(&ptdev->pm.recovery_needed, 1, 0) == 1) > > I'm unclear what this atomic achieves. At first glance it appears > pointless: with this change if panthor_device_resume() fails then > recovery_needed is set to 1. So logically if ret != 0 then also > recovery_needed == 1. > > My second thought was is this to avoid races? If multiple threads are > calling this then only one will win the cmpxchg and call > pm_runtime_set_suspended. But it's not safe - it's quite possible for > the first thread to get past the cmpxchg and be suspended before the > second thread comes along and reaches the same point - leading to > multiple calls to pm_runtime_set_suspended(). Yes, it was here to avoid the race. I don't think there's a risk of multiple threads calling pm_runtime_set_suspended() without actually needing such a call, because we won't reach panthor_device_resume() until the runtime_error has been cleared (runtime PM bails out early with a -EINVAL). So, in practice, there's no way two threads can see a recovery_needed=1 unless the error has already been cleared by the other thread and the second thread triggered another resume error, in which case the second pm_runtime_set_suspended() call is legit. But now that you mention it, it indeed doesn't prevent the second thread to call pm_runtime_resume_and_get() before the PM runtime_error has been cleared, leading to potential spurious errors, so that's annoying.
diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c index 353f3aabef42..d3276b936141 100644 --- a/drivers/gpu/drm/panthor/panthor_device.c +++ b/drivers/gpu/drm/panthor/panthor_device.c @@ -486,6 +486,7 @@ int panthor_device_resume(struct device *dev) err_set_suspended: atomic_set(&ptdev->pm.state, PANTHOR_DEVICE_PM_STATE_SUSPENDED); + atomic_set(&ptdev->pm.recovery_needed, 1); return ret; } diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h index 0e68f5a70d20..cc74e99e53f9 100644 --- a/drivers/gpu/drm/panthor/panthor_device.h +++ b/drivers/gpu/drm/panthor/panthor_device.h @@ -9,6 +9,7 @@ #include <linux/atomic.h> #include <linux/io-pgtable.h> #include <linux/regulator/consumer.h> +#include <linux/pm_runtime.h> #include <linux/sched.h> #include <linux/spinlock.h> @@ -180,6 +181,9 @@ struct panthor_device { * is suspended. */ struct page *dummy_latest_flush; + + /** @recovery_needed: True when a resume attempt failed. */ + atomic_t recovery_needed; } pm; /** @profile_mask: User-set profiling flags for job accounting. */ @@ -243,6 +247,19 @@ int panthor_device_mmap_io(struct panthor_device *ptdev, int panthor_device_resume(struct device *dev); int panthor_device_suspend(struct device *dev); +static inline int panthor_device_resume_and_get(struct panthor_device *ptdev) +{ + int ret = pm_runtime_resume_and_get(ptdev->base.dev); + + /* If the resume failed, we need to clear the runtime_error, which we + * can done by forcing the RPM state to suspended. + */ + if (ret && atomic_cmpxchg(&ptdev->pm.recovery_needed, 1, 0) == 1) + pm_runtime_set_suspended(ptdev->base.dev); + + return ret; +} + enum drm_panthor_exception_type { DRM_PANTHOR_EXCEPTION_OK = 0x00, DRM_PANTHOR_EXCEPTION_TERMINATED = 0x04, diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c index 1498c97b4b85..b7a9adc918e3 100644 --- a/drivers/gpu/drm/panthor/panthor_drv.c +++ b/drivers/gpu/drm/panthor/panthor_drv.c @@ -763,7 +763,7 @@ static int panthor_query_timestamp_info(struct panthor_device *ptdev, { int ret; - ret = pm_runtime_resume_and_get(ptdev->base.dev); + ret = panthor_device_resume_and_get(ptdev); if (ret) return ret; diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c index 97ed5fe5a191..77b184c3fb0c 100644 --- a/drivers/gpu/drm/panthor/panthor_sched.c +++ b/drivers/gpu/drm/panthor/panthor_sched.c @@ -2364,7 +2364,7 @@ static void tick_work(struct work_struct *work) if (!drm_dev_enter(&ptdev->base, &cookie)) return; - ret = pm_runtime_resume_and_get(ptdev->base.dev); + ret = panthor_device_resume_and_get(ptdev); if (drm_WARN_ON(&ptdev->base, ret)) goto out_dev_exit; @@ -3131,7 +3131,7 @@ queue_run_job(struct drm_sched_job *sched_job) return dma_fence_get(job->done_fence); } - ret = pm_runtime_resume_and_get(ptdev->base.dev); + ret = panthor_device_resume_and_get(ptdev); if (drm_WARN_ON(&ptdev->base, ret)) return ERR_PTR(ret);
When the runtime PM resume callback returns an error, it puts the device in a state where it can't be resumed anymore. Make sure we can recover from such transient failures by calling pm_runtime_set_suspended() explicitly after a pm_runtime_resume_and_get() failure. Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> --- drivers/gpu/drm/panthor/panthor_device.c | 1 + drivers/gpu/drm/panthor/panthor_device.h | 17 +++++++++++++++++ drivers/gpu/drm/panthor/panthor_drv.c | 2 +- drivers/gpu/drm/panthor/panthor_sched.c | 4 ++-- 4 files changed, 21 insertions(+), 3 deletions(-)