[Intel-gfx] [PATCH v2 4/6] drm/i915: Disable PSR when a PSR aux error happen
Souza, Jose
jose.souza at intel.com
Wed Oct 24 23:31:05 UTC 2018
On Wed, 2018-10-24 at 16:22 -0700, Dhinakaran Pandiyan wrote:
> On Wed, 2018-10-24 at 15:08 -0700, Dhinakaran Pandiyan wrote:
> > On Sat, 2018-10-20 at 00:12 +0000, Souza, Jose wrote:
> > > On Fri, 2018-10-19 at 16:14 -0700, Dhinakaran Pandiyan wrote:
> > > > On Wed, 2018-10-10 at 17:41 -0700, José Roberto de Souza wrote:
> > > > > While PSR is active hardware will do aux transactions by it
> > > > > self
> > > > > to
> > > > > wakeup sink to receive a new frame when necessary. If that
> > > > > transaction is not acked by sink, hardware will trigger this
> > > > > interruption.
> > > > >
> > > > > So let's disable PSR as it is a hint that there is problem
> > > > > with
> > > > > this
> > > > > sink.
> > > > >
> > > > > The removed FIXME was asking to manually train the link but
> > > > > we
> > > > > don't
> > > > > need to do that as by spec sink should do a short pulse when
> > > > > it
> > > > > is
> > > > > out of sync with source, we just need to make sure it is
> > > > > awaken
> > > > > and
> > > > > the SDP header with PSR disable will trigger this condition.
> > > > >
> > > > > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > > > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > > > ---
> > > > > drivers/gpu/drm/i915/i915_drv.h | 1 +
> > > > > drivers/gpu/drm/i915/intel_psr.c | 39
> > > > > ++++++++++++++++++++++++++++
> > > > > ----
> > > > > 2 files changed, 36 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > > > > b/drivers/gpu/drm/i915/i915_drv.h
> > > > > index 3017ef037fed..e8ba00dd2c51 100644
> > > > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > > > @@ -638,6 +638,7 @@ struct i915_psr {
> > > > > u8 sink_sync_latency;
> > > > > ktime_t last_entry_attempt;
> > > > > ktime_t last_exit;
> > > > > + u32 irq_aux_error;
> > > > > };
> > > > >
> > > > > enum intel_pch {
> > > > > diff --git a/drivers/gpu/drm/i915/intel_psr.c
> > > > > b/drivers/gpu/drm/i915/intel_psr.c
> > > > > index 70d4e26e17b5..ad09130cb4ad 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_psr.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_psr.c
> > > > > @@ -159,10 +159,16 @@ void intel_psr_irq_handler(struct
> > > > > drm_i915_private *dev_priv, u32 psr_iir)
> > > > > BIT(TRANSCODER_C);
> > > > >
> > > > > for_each_cpu_transcoder_masked(dev_priv,
> > > > > cpu_transcoder,
> > > > > transcoders) {
> > > > > - /* FIXME: Exit PSR and link train manually when
> > > > > this
> > > > > happens. */
> > > > > - if (psr_iir & EDP_PSR_ERROR(cpu_transcoder))
> > > > > - DRM_DEBUG_KMS("[transcoder %s] PSR aux
> > > > > error\n",
> > > > > - transcoder_name(cpu_trans
> > > > > coder));
> > > > > + if (psr_iir & EDP_PSR_ERROR(cpu_transcoder)) {
> > > > > + DRM_WARN("[transcoder %s] PSR aux
> > > > > error\n",
> > > > > + transcoder_name(cpu_transcoder
> > > > > ));
> > > >
> > > > Downgrade this to debug since the error is handled in the
> > > > driver?
> > >
> > > I think is better keep as DRM_WARN so it is shown in regular
> > > kernel
> > > logs this way if a user opens a bug complaning why PSR is
> > > disabled
> > > we
> > > can check that is because of PSR aux error.
> > >
> > > > > +
> > > > > + spin_lock(&dev_priv->irq_lock);
> >
> > This lock isn't needed either. How about setting a bool only if the
> > transcoder is eDP and then scheduling a disable.
> >
> > > > > + dev_priv->psr.irq_aux_error |=
> > > > > BIT(cpu_transcoder);
> > > >
> > > > Just ignore the non eDP bits, I don't think we want to do
> > > > anything
> > > > with
> > > > the information that some other bit was set.
> > > >
> > > > > + spin_unlock(&dev_priv->irq_lock);
> > > > > +
> > > > > + schedule_work(&dev_priv->psr.work);
> > > > > + }
> > > > >
> > > > > if (psr_iir &
> > > > > EDP_PSR_PRE_ENTRY(cpu_transcoder)) {
> > > > > dev_priv->psr.last_entry_attempt =
> > > > > time_ns;
> > > > > @@ -893,11 +899,36 @@ int intel_psr_set_debugfs_mode(struct
> > > > > drm_i915_private *dev_priv,
> > > > > return ret;
> > > > > }
> > > > >
> > > > > +static void intel_psr_handle_irq(struct drm_i915_private
> > > > > *dev_priv)
> > > > > +{
> > > > > + struct i915_psr *psr = &dev_priv->psr;
> > > > > + u32 irq_aux_error;
> > > > > +
> > > > > + spin_lock_irq(&dev_priv->irq_lock);
> > > > > + irq_aux_error = psr->irq_aux_error;
> > > > > + psr->irq_aux_error = 0;
> > > >
> > > > A subsequent modeset will enable PSR again. I don't expect a
> > > > modeset
> > > > to
> > > > to be able to fix an AUX wake up failure, so might as well
> > > > disable
> > > > it
> > > > for good.
> > >
> > > Add another field to do that or set sink_support=false? I guess
> > > PSR
> > > short pulses errors should also disable it good too?
> >
> > Reusing sink_support will get confusing, particularly because it is
> > exposed in debugfs.
> >
> > > > > + spin_unlock_irq(&dev_priv->irq_lock);
> > > > > +
> > > > > + /* right now PSR is only enabled in eDP */
> > > >
> > > > "right now" implies that PSR could be enabled for non eDP
> > > > ports,
> > > > but
> > > > that's not the case.
> > > >
> > > >
> > > > > + WARN_ON(irq_aux_error & ~BIT(TRANSCODER_EDP));
> > > >
> > > > This should go away if you ignore non-EDP bits, and a stack
> > > > trace
> > > > isn't
> > > > particularly useful anyway.
> > >
> > > Okay I will remove this handlings for other transcoders.
> > >
> > > > > +
> > > > > + mutex_lock(&psr->lock);
> > > >
> > > > Is this sufficient? Don't we have to serialize against ongoing
> > > > modesets
> > > > like we do for debugfs enable/disable. The disable sequence in
> > > > bspec
> > > > calls out a running pipe and port as pre-requisites.
> > >
> > > HW will only send a aux transaction when exiting PSR, in this
> > > cases
> > > pipe will always be running:
> >
> > Sure, but psr_work() can run after the pipe is disabled.
> >
> > However, psr.enabled should take care of not writing to PSR_CTL if
> > the
> > pipe was already disabled. The question now is if we were in the
> > middle
> > of a modeset, disabling PSR here would have no effect if encoders
> > are
> > enabled after this point.
> >
> Another issue is the wait for idle under psr.lock, not a good idea to
> have modesets waiting for that lock.
When doing a modeset it would wait for PSR idle anyways as we can only
disable the pipe if PSR is idle. But waiting here allow us to send the
wake command after hardware already tried to exit PSR.
>
> > > - exiting because of changes in the screen
> > > - exiting because pipe will be disabled
> > > - exiting because of PSR error
> > >
> > > > Ccing Ville and Maarten to get their opinion on this.
> > > >
> > > > > +
> > > > > + intel_psr_disable_locked(psr->dp);
> > > > > + /* let's make sure that sink is awaken */
> > > > > + drm_dp_dpcd_writeb(&psr->dp->aux, DP_SET_POWER,
> > > > > DP_SET_POWER_D0);
> > > >
> > > > Given that the hardware initiated AUX write failed, I would
> > > > recommend
> > > > reading back the sink PSR status to make sure disable worked.
> > >
> > > And in case of reading error or the value is not set try again?
> > > This
> > > could fall into a infite loop. intel_dp_aux_xfer() already try to
> > > do
> > > the transaction 5 times I guess if if failed the sink crashed and
> > > there
> > > is no recover.
> > >
> >
> > I was thinking of printing an error here so that we know error
> > recovery
> > did not work.
> >
> >
> > > > > +
> > > > > + mutex_unlock(&dev_priv->psr.lock);
> > > > > +}
> > > > > +
> > > > > static void intel_psr_work(struct work_struct *work)
> > > > > {
> > > > > struct drm_i915_private *dev_priv =
> > > > > container_of(work, typeof(*dev_priv),
> > > > > psr.work);
> > > > >
> > > > > + if (READ_ONCE(dev_priv->psr.irq_aux_error))
> > > > > + intel_psr_handle_irq(dev_priv);
> >
> > Why not create a new work item for disable? I don't see why
> > intel_psr_work() needs to be reused for a completely different
> > reason.
> >
> > > > If psr_work() was already executing and past this check,
> > > > schedule_work() in intel_psr_irq_handler will return a failure
> > > > and
> > > > disable PSR would now depend on getting an invalidate and flush
> > > > operation. We should disable PSR without any dependency on
> > > > flush
> > > > or
> > > > invalidate.
> > >
> > > For what I checked in the schedule_work() code if the work is
> > > running
> > > and there is a call to schedule_work() it will be schedule again.
> > >
> >
> > From the documentation,
> > /**
> > * schedule_work - put work task in global workqueue
> > * @work: job to be done
> > *
> > * Returns %false if @work was already on the kernel-global
> > workqueue
> > and
> > * %true otherwise.
> > *
> >
> > > >
> > > > > +
> > > > > mutex_lock(&dev_priv->psr.lock);
> > > > >
> > > > > if (!dev_priv->psr.enabled)
> > >
> > > _______________________________________________
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> > > Intel-gfx at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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