linux-kernel - Re: [Intel-gfx] [PATCH] drm/i915: intel_hpd_init(): Don't check connectors for an encoder

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Message-ID: <20160105200951.GT8076@phenom.ffwll.local>
Date:	Tue, 5 Jan 2016 21:09:51 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Lyude <cpaul@...hat.com>
Cc:	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Benjamin Tissoires <btissoir@...hat.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: intel_hpd_init(): Don't check
 connectors for an encoder

On Tue, Jan 05, 2016 at 09:05:49PM +0100, Daniel Vetter wrote:
> On Tue, Jan 05, 2016 at 02:53:08PM -0500, Lyude wrote:
> > There's no reason to check for an active encoder when setting up hpd,
> > especially since a disconnected connector isn't going to have an encoder
> > in the first place. This fixes reprobing display connectors on resume.
> > 
> > Signed-off-by: Lyude <cpaul@...hat.com>
> > ---
> > After some talking with danvet on IRC, I learned that calling
> > drm_helper_hpd_irq_event() does actually trigger a full reprobe of each
> > connector's status. It turns out this is the actual reason reprobing on resume
> > hasn't been working (this was observed on a T440s):
> > 
> > 	- We call hpd_init()
> > 	- We check each connector for a couple of things before marking
> > 	  connector->polled with DRM_CONNECTOR_POLL_HPD, one of which is an
> > 	  active encoder. Of course, a disconnected port won't have an active
> > 	  encoder, so we don't add the flag to any of the connector's.
> > 	- We call drm_helper_hpd_irq_event()
> > 	- drm_helper_irq_event() checks each connector for the
> > 	  DRM_CONNECTOR_POLL_HPD flag. The only one that has it is eDP-1, so we
> > 	  skip reprobing each connector except that one.
> 
> The above explanation should be part of the commit message, otherwise it's
> hard to understand the impact of this fix.
> 
> Fixes: 0e32b39ceed6 ("drm/i915: add DP 1.2 MST support (v0.7)")
> Cc: stable@...r.kernel.org
> 
> Unfortunately Dave doesn't explain in his MST commit why he's done this.
> Dave? I can't come up with a reason, but better to test that. Lyude?
> 
> Anyway looks good to me.
> 
> Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

Need to retract my r-b. MST connectors don't have a fixed fake encoder,
and the intel_connector->encoder link is done at link time and not static.

We need to filter out MST connectors here, otherwise this will go boom.
While at it, can you please line-break this properly to appease
checkpatch?
-Daniel

> 
> > 
> >  drivers/gpu/drm/i915/intel_hotplug.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
> > index b177857..18797bc 100644
> > --- a/drivers/gpu/drm/i915/intel_hotplug.c
> > +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> > @@ -468,7 +468,7 @@ void intel_hpd_init(struct drm_i915_private *dev_priv)
> >  	list_for_each_entry(connector, &mode_config->connector_list, head) {
> >  		struct intel_connector *intel_connector = to_intel_connector(connector);
> >  		connector->polled = intel_connector->polled;
> > -		if (connector->encoder && !connector->polled && I915_HAS_HOTPLUG(dev) && intel_connector->encoder->hpd_pin > HPD_NONE)
> > +		if (!connector->polled && I915_HAS_HOTPLUG(dev) && intel_connector->encoder->hpd_pin > HPD_NONE)
> >  			connector->polled = DRM_CONNECTOR_POLL_HPD;
> >  		if (intel_connector->mst_port)
> >  			connector->polled = DRM_CONNECTOR_POLL_HPD;
> > -- 
> > 2.5.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@...ts.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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