On Sat, 12 Sep 2026 00:28:07 +0100 Adrián Larumbe <[email protected]> wrote:
> During device probe(), failure to do a PM get() will leave the usage_count > set to 0, which is the value assigned at device creation time. That means > when the autosuspend delay expires, runtime suspend callback won't be > invoked, so the device will remain powered on forever. > > On top of that, failure to call PM put() during device unplug means > Panfrost device's PM usage_count increases monotonically for every new > module reload. > > The outcome of both of the above meant that: > > - Devfreq OPP transition notifications would be printed all the time, > even when no jobs are being submitted. This quickly fills the kernel > ring buffer with junk. > - Because MMU interrupts are only enabled when the device is reset, > the very first job targeting the tiler heap BO after device probe() > would always time out, since the driver's PM runtime resume callback > would not be invoked. > > To fix the above: > - Manually adjust the PM refcnt at device probe and removal time. > - Ensure pm_runtime_dont_use_autosuspend is called in the wind-down path. > - Call pm_runtime_put_autosuspend() when device is ready to accept jobs > - Move pm_runtime_set_suspended() before panfrost_device_fini() so that > resource unwinding happens in the opposite order as initialisation. > > Signed-off-by: Adrián Larumbe <[email protected]> > Fixes: 635430797d3f ("drm/panfrost: Rework runtime PM initialization") > Fixes: 876b15d2c88d ("drm/panfrost: Fix module unload") > --- > drivers/gpu/drm/panfrost/panfrost_drv.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c > b/drivers/gpu/drm/panfrost/panfrost_drv.c > index 55fc22e8d4d4..a3eff77add55 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_drv.c > +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c > @@ -854,6 +854,7 @@ static int panfrost_probe(struct platform_device *pdev) > > pm_runtime_set_active(pfdev->base.dev); > pm_runtime_mark_last_busy(pfdev->base.dev); > + pm_runtime_get_noresume(pfdev->base.dev); > pm_runtime_enable(pfdev->base.dev); > pm_runtime_set_autosuspend_delay(pfdev->base.dev, 50); /* ~3 frames */ > pm_runtime_use_autosuspend(pfdev->base.dev); > @@ -866,13 +867,16 @@ static int panfrost_probe(struct platform_device *pdev) > if (err < 0) > goto err_out1; > > + pm_runtime_put_autosuspend(pfdev->base.dev); > > return 0; > > err_out1: > + pm_runtime_dont_use_autosuspend(pfdev->base.dev); > pm_runtime_disable(pfdev->base.dev); > - panfrost_device_fini(pfdev); > + pm_runtime_put_noidle(pfdev->base.dev); > pm_runtime_set_suspended(pfdev->base.dev); > + panfrost_device_fini(pfdev); Not an issue per-se, because put_noidle() is a NOP, but I think it'd be easier to reason about with this order: pm_runtime_dont_use_autosuspend(pfdev->base.dev); pm_runtime_disable(pfdev->base.dev); panfrost_device_fini(pfdev); pm_runtime_set_suspended(pfdev->base.dev); pm_runtime_put_noidle(pfdev->base.dev); This makes it clear that panfrost_device_fini() assumes the device is resumed when it's called and suspended when it returns. > err_out0: > return err; > } > @@ -884,9 +888,11 @@ static void panfrost_remove(struct platform_device *pdev) > drm_dev_unregister(&pfdev->base); > > pm_runtime_get_sync(pfdev->base.dev); > + pm_runtime_dont_use_autosuspend(pfdev->base.dev); > + pm_runtime_put_noidle(pfdev->base.dev); > pm_runtime_disable(pfdev->base.dev); Let's keep the order consistent with the probe path: pm_runtime_dont_use_autosuspend(pfdev->base.dev); pm_runtime_disable(pfdev->base.dev); panfrost_device_fini(pfdev); pm_runtime_set_suspended(pfdev->base.dev); pm_runtime_put_noidle(pfdev->base.dev); I also think this deserves comments to explain the noresume/noidle dance (device_init/fini take care of clks internally, and when they return the device is resumed/suspended, so all we have to is update the state, and acquire a ref). > - panfrost_device_fini(pfdev); > pm_runtime_set_suspended(pfdev->base.dev); > + panfrost_device_fini(pfdev); > } > > static ssize_t profiling_show(struct device *dev, >
