Hi Doug,
On Tue, Jan 9, 2024 at 6:46 AM Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Wed, Dec 27, 2023 at 2:43 AM Pin-yen Lin <treapking@xxxxxxxxxxxx> wrote:
> >
> > Disable the autosuspend of runtime PM and use completion to make sure
> > ps8640_suspend() is called in ps8640_atomic_post_disable().
> >
> > The ps8640 bridge seems to expect everything to be power cycled at the
> > disable process, but sometimes ps8640_aux_transfer() holds the runtime
> > PM reference and prevents the bridge from suspend.
> >
> > Instead of force powering off the bridge and taking the risk of breaking
> > the AUX communication, disable the autosuspend and wait for
> > ps8640_suspend() being called here, and re-enable the autosuspend
> > afterwards. With this approach, the bridge should be suspended after
> > the current ps8640_aux_transfer() completes.
> >
> > Fixes: 826cff3f7ebb ("drm/bridge: parade-ps8640: Enable runtime power management")
> > Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx>
> > ---
> >
> > drivers/gpu/drm/bridge/parade-ps8640.c | 33 +++++++++++++++++++++++++-
> > 1 file changed, 32 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index 8161b1a1a4b1..f8ea486a76fd 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -107,6 +107,7 @@ struct ps8640 {
> > struct device_link *link;
> > bool pre_enabled;
> > bool need_post_hpd_delay;
> > + struct completion suspend_completion;
> > };
> >
> > static const struct regmap_config ps8640_regmap_config[] = {
> > @@ -417,6 +418,8 @@ static int __maybe_unused ps8640_suspend(struct device *dev)
> > if (ret < 0)
> > dev_err(dev, "cannot disable regulators %d\n", ret);
> >
> > + complete_all(&ps_bridge->suspend_completion);
> > +
> > return ret;
> > }
> >
> > @@ -465,11 +468,37 @@ static void ps8640_atomic_post_disable(struct drm_bridge *bridge,
> > struct drm_bridge_state *old_bridge_state)
> > {
> > struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> > + struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
> >
> > ps_bridge->pre_enabled = false;
> >
> > ps8640_bridge_vdo_control(ps_bridge, DISABLE);
> > - pm_runtime_put_sync_suspend(&ps_bridge->page[PAGE0_DP_CNTL]->dev);
> > +
> > + /*
> > + * The ps8640 bridge seems to expect everything to be power cycled at
> > + * the disable process, but sometimes ps8640_aux_transfer() holds the
> > + * runtime PM reference and prevents the bridge from suspend.
> > + * Instead of force powering off the bridge and taking the risk of
> > + * breaking the AUX communication, disable the autosuspend and wait for
> > + * ps8640_suspend() being called here, and re-enable the autosuspend
> > + * afterwards. With this approach, the bridge should be suspended after
> > + * the current ps8640_aux_transfer() completes.
> > + */
> > + reinit_completion(&ps_bridge->suspend_completion);
> > + pm_runtime_dont_use_autosuspend(dev);
> > + pm_runtime_put_sync_suspend(dev);
> > +
> > + /*
> > + * Mostly the suspend completes under 10 ms, but sometimes it could
> > + * take 708 ms to complete. Set the timeout to 2000 ms here to be
> > + * extra safe.
> > + */
> > + if (!wait_for_completion_timeout(&ps_bridge->suspend_completion,
> > + msecs_to_jiffies(2000))) {
> > + dev_warn(dev, "Failed to wait for the suspend completion\n");
> > + }
> > +
> > + pm_runtime_use_autosuspend(dev);
>
> Thanks for tracking this down! I agree with your analysis and it seems
> like we've got to do something about it.
>
> I spent a little time trying to think about a cleaner way. What do you
> think about adding a "aux_transfer" mutex? You'd grab this mutex for
> the entire duration of ps8640_aux_transfer() and
> ps8640_atomic_post_disable(). That way you don't need the weird
> completion / timeout and don't need to hackily turn off/on
> autosuspend. You shouldn't need the mutex in
> ps8640_wait_hpd_asserted() because that will never be called at the
> same time as ps8640_atomic_post_disable().
>
> -Doug
Hi Doug,
Thanks for the suggestion! I tried that approach and it fixes the issue as well.
I'll send out another patch with that approach.
Regards,
Pin-yen
