linux-kernel - [PATCH 4.9 03/66] drm: Schedule the output_poll_work with 1s delay if we have delayed event

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Date:   Tue, 31 Jan 2017 06:36:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Ujfalusi <peter.ujfalusi@...com>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 4.9 03/66] drm: Schedule the output_poll_work with 1s delay if we have delayed event

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Ujfalusi <peter.ujfalusi@...com>

commit 68f458eec7069d618a6c884ca007426e0cea411b upstream.

Instead of scheduling the work to handle the initial delayed event, use 1s
delay.

This delay should not be needed, but Optimus/nouveau will fail in a
mysterious way if the delayed event is handled as soon as possible like it
is done in drm_helper_probe_single_connector_modes() in case the poll
was enabled before.

Reverting 339fd36238dd would give back the 10 sec (!) delay to handle the
delayed event. Adding 1sec delay to the poll_work is enough to work around
the issue in Optimus setups and gives shorter response on handling the
initial delayed event.

Fixes: 339fd36238dd ("drm: drm_probe_helper: Fix output_poll_work scheduling")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
[danvet: Add FIXME to the comment to make it stick out more.]
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170109143158.21917-1-peter.ujfalusi@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_probe_helper.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -143,8 +143,18 @@ void drm_kms_helper_poll_enable_locked(s
 	}
 
 	if (dev->mode_config.delayed_event) {
+		/*
+		 * FIXME:
+		 *
+		 * Use short (1s) delay to handle the initial delayed event.
+		 * This delay should not be needed, but Optimus/nouveau will
+		 * fail in a mysterious way if the delayed event is handled as
+		 * soon as possible like it is done in
+		 * drm_helper_probe_single_connector_modes() in case the poll
+		 * was enabled before.
+		 */
 		poll = true;
-		delay = 0;
+		delay = HZ;
 	}
 
 	if (poll)