linux-kernel - [PATCH] drm: drm_probe_helper: Fix output_poll

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Date:   Mon, 29 Aug 2016 12:50:22 +0300
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     <airlied@...ux.ie>, <daniel.vetter@...ll.ch>
CC:     <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <ville.syrjala@...ux.intel.com>, <tomi.valkeinen@...com>
Subject: [PATCH] drm: drm_probe_helper: Fix output_poll_work scheduling

drm_kms_helper_poll_enable_locked() should check if we have delayed event
pending and if we have, schedule the work to run without delay.

Currently the output_poll_work is only scheduled if any of the connectors
have DRM_CONNECTOR_POLL_CONNECT or DRM_CONNECTOR_POLL_DISCONNECT with
DRM_OUTPUT_POLL_PERIOD delay. It does not matter if we have delayed event
already registered to be handled. The detection will be delayd by
DRM_OUTPUT_POLL_PERIOD in any case.
Furthermore if none of the connectors are marked as POLL_CONNECT or
POLL_DISCONNECT because all connectors are either POLL_HPD or they are
always connected: the output_poll_work will not run at all even if we
have delayed event marked.

When none of the connectors require polling, their initial status change
from unknown to connected/disconnected is not going to be handled until
the first kms application starts or if we have fb console enabled.

With this change we can react more quickly to output status changes after
enabling the poll but most importantly it will correct the behavior when
none of the connector have POLL_CONNECT or POLL_DISCONNECT flag set - they
are either POLL_HPD or the .polled is 0. The initial status change is going
to be handled correctly as well.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
---
 drivers/gpu/drm/drm_probe_helper.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index a0df377d7d1c..f6b64d7d3528 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -129,6 +129,7 @@ void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
 {
 	bool poll = false;
 	struct drm_connector *connector;
+	unsigned long delay = DRM_OUTPUT_POLL_PERIOD;

 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));

@@ -141,8 +142,13 @@ void drm_kms_helper_poll_enable_locked(struct drm_device *dev)
 			poll = true;
 	}

+	if (dev->mode_config.delayed_event) {
+		poll = true;
+		delay = 0;
+	}
+
 	if (poll)
-		schedule_delayed_work(&dev->mode_config.output_poll_work, DRM_OUTPUT_POLL_PERIOD);
+		schedule_delayed_work(&dev->mode_config.output_poll_work, delay);
 }
 EXPORT_SYMBOL(drm_kms_helper_poll_enable_locked);

-- 
2.9.3