Re: [PATCH v3] drm/i915: intel_hpd_init(): Fix suspend/resume reprobing

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Jan 07, 2016 at 10:43:28AM -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 that one.
> 
> In addition, we also 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.
> 
> Changes since V1:
> * 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
> 
> Changes since V2:
> * Put patch changelog above Signed-off-by
> * Follow Daniel Vetter's suggestion for making the code here a bit more
>   legible
> 
> Fixes: 0e32b39ceed6 ("drm/i915: add DP 1.2 MST support (v0.7)")
> Cc: stable@vger.kernel.org
> Signed-off-by: Lyude <cpaul@redhat.com>

Awesome, and merged to drm-intel.

Thanks, Daniel

> ---
>  drivers/gpu/drm/i915/intel_hotplug.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
> index b177857..d7a6437 100644
> --- a/drivers/gpu/drm/i915/intel_hotplug.c
> +++ b/drivers/gpu/drm/i915/intel_hotplug.c
> @@ -468,9 +468,14 @@ 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;
> +
> +		/* 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;
>  	}
>  
> -- 
> 2.5.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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