[Intel-gfx] [PATCH v2 4/6] drm/i915: Disable PSR when a PSR aux error happen
Dhinakaran Pandiyan
dhinakaran.pandiyan at intel.com
Wed Oct 24 22:08:22 UTC 2018
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_transcoder));
> > > + 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.
> - 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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