linux-kernel - Re: [Intel-gfx] [PATCH v2] drm/i915: intel_hpd_init(): Fix suspend/resume reprobing

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Message-ID: <20160106072743.GV8076@phenom.ffwll.local>
Date:	Wed, 6 Jan 2016 08:27:43 +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>,
	stable@...r.kernel.org
Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: intel_hpd_init(): Fix
 suspend/resume reprobing

On Tue, Jan 05, 2016 at 04:15:30PM -0500, Lyude wrote:
> This fixes reprobing of display connectors on resume. 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
> 	  connectors.
> 	- 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 for that one.
> 
> In addition, we now avoid setting connector->polled to
> DRM_CONNECTOR_POLL_HPD for MST connectors, since their reprobing is handled
> by the mst helpers. This is probably what was originally intended to happen
> here anyway.
> 
> Fixes: 0e32b39ceed6 ("drm/i915: add DP 1.2 MST support (v0.7)")
> Cc: stable@...r.kernel.org
> Signed-off-by: Lyude <cpaul@...hat.com>
> ---
> 				    Changes
> * Use the explanation of the issue as the commit message instead
> * Change the title of the commit, since this does more then just stop a check
>   for an encoder now
> * Add "Fixes" line for the patch that introduced this regression
> * Don't enable DRM_CONNECTOR_POLL_HPD for mst connectors

For drm/i915 I prefer when the patch changelog is above the s-o-b section,
with v2: v3: ... headings.
> 
>  drivers/gpu/drm/i915/intel_hotplug.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
> index b177857..51ecf0b4 100644
> --- a/drivers/gpu/drm/i915/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> @@ -468,9 +468,9 @@ 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)
> -			connector->polled = DRM_CONNECTOR_POLL_HPD;
> -		if (intel_connector->mst_port)
> +		if (!connector->polled && !intel_connector->mst_port &&
> +		    I915_HAS_HOTPLUG(dev) &&
> +		    intel_connector->encoder->hpd_pin > HPD_NONE)
>  			connector->polled = DRM_CONNECTOR_POLL_HPD;

Hm, on 2nd thought we could clarify this further like this:

	list_for_each_entry(...) {
		...

		/* MST has a dynamic intel_connector->encoder and it's
		 * reprobing is all handled by the MST helpers. */
		if (intel_connector->mst_port)
			continue;

		if (!connector->polled && I915_HAS_HOTPLUG(dev) &&
		    intel_connector->encoder->hpd_pin > HPD_NONE)
			connector->polled = DRM_CONNECTOR_POLL_HPD;

	}

That yields even tidier code and gives us a place for a comment. Can you
pls respin once more?

Thanks, Daniel

>  	}
>  
> -- 
> 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
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