linux-kernel - Re: [PATCH] drm/i915: Synchronize connectors states when switching from poll to irq

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Date:   Wed, 19 Jul 2017 23:11:21 -0700
From:   Manasi Navare <manasi.d.navare@...el.com>
To:     Paul Kocialkowski <paul.kocialkowski@...ux.intel.com>
Cc:     intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH] drm/i915: Synchronize connectors states when switching
 from poll to irq

On Tue, Jul 18, 2017 at 03:11:42PM +0300, Paul Kocialkowski wrote:
> On Mon, 2017-06-26 at 15:32 +0300, Paul Kocialkowski wrote:
> > After detecting an IRQ storm, hotplug detection will switch from
> > irq-based detection to poll-based detection. After a short delay or
> > when resetting storm detection from debugfs, detection will switch
> > back to being irq-based.
> > 
> > However, it may occur that polling does not have enough time to detect
> > the current connector state when that second switch takes place. Thus,
> > this sets the appropriate hotplug event bits for the concerned
> > connectors and schedules the hotplug work, that will ensure the
> > connectors states are in sync when switching back to irq.
> > 
> > Without this, no irq will be triggered and the hpd change will be
> > lost.
> 
> Does anyone have feedback to provide on this?
> It looks like it should be a no-brainer.
> 
> Cheers,
> 
> Paul
> 
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...ux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_hotplug.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_hotplug.c
> > b/drivers/gpu/drm/i915/intel_hotplug.c
> > index f1200272a699..29f55480b0bb 100644
> > --- a/drivers/gpu/drm/i915/intel_hotplug.c
> > +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> > @@ -218,9 +218,13 @@ static void
> > intel_hpd_irq_storm_reenable_work(struct work_struct *work)
> >  			struct intel_connector *intel_connector =
> > to_intel_connector(connector);
> >  
> >  			if (intel_connector->encoder->hpd_pin == i) {

So if this hpd pin in intel_connector->encoder is set then that
means it got the hpd but because connector->polled is != intel_connector->polled
polling didnt detect that connector.
Is that what you are trying to do here?

Manasi

> > -				if (connector->polled !=
> > intel_connector->polled)
> > +				if (connector->polled !=
> > intel_connector->polled) {
> >  					DRM_DEBUG_DRIVER("Reenabling
> > HPD on connector %s\n",
> >  							 connector-
> > >name);
> > +
> > +					dev_priv->hotplug.event_bits
> > |= (1 << i);
> > +				}
> > +
> >  				connector->polled = intel_connector-
> > >polled;
> >  				if (!connector->polled)
> >  					connector->polled =
> > DRM_CONNECTOR_POLL_HPD;
> > @@ -232,6 +236,8 @@ static void
> > intel_hpd_irq_storm_reenable_work(struct work_struct *work)
> >  		dev_priv->display.hpd_irq_setup(dev_priv);
> >  	spin_unlock_irq(&dev_priv->irq_lock);
> >  
> > +	schedule_work(&dev_priv->hotplug.hotplug_work);
> > +
> >  	intel_runtime_pm_put(dev_priv);
> >  }
> >  
> -- 
> Paul Kocialkowski <paul.kocialkowski@...ux.intel.com>
> Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo, Finland
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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