linux-kernel - [PATCH 4.4 18/28] drm/nouveau/drm/nouveau: Use pm_runtime_get_noresume() in connector

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Date:   Thu, 27 Sep 2018 11:06:42 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        Karol Herbst <kherbst@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Lukas Wunner <lukas@...ner.de>, Ben Skeggs <bskeggs@...hat.com>
Subject: [PATCH 4.4 18/28] drm/nouveau/drm/nouveau: Use pm_runtime_get_noresume() in connector_detect()

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

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

From: Lyude Paul <lyude@...hat.com>

commit 6833fb1ec120bf078e1a527c573a09d4de286224 upstream.

It's true we can't resume the device from poll workers in
nouveau_connector_detect(). We can however, prevent the autosuspend
timer from elapsing immediately if it hasn't already without risking any
sort of deadlock with the runtime suspend/resume operations. So do that
instead of entirely avoiding grabbing a power reference.

Signed-off-by: Lyude Paul <lyude@...hat.com>
Reviewed-by: Karol Herbst <kherbst@...hat.com>
Acked-by: Daniel Vetter <daniel@...ll.ch>
Cc: stable@...r.kernel.org
Cc: Lukas Wunner <lukas@...ner.de>
Signed-off-by: Ben Skeggs <bskeggs@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/nouveau/nouveau_connector.c |   20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -253,12 +253,16 @@ nouveau_connector_detect(struct drm_conn
 		nv_connector->edid = NULL;
 	}
 
-	/* Outputs are only polled while runtime active, so acquiring a
-	 * runtime PM ref here is unnecessary (and would deadlock upon
-	 * runtime suspend because it waits for polling to finish).
+	/* Outputs are only polled while runtime active, so resuming the
+	 * device here is unnecessary (and would deadlock upon runtime suspend
+	 * because it waits for polling to finish). We do however, want to
+	 * prevent the autosuspend timer from elapsing during this operation
+	 * if possible.
 	 */
-	if (!drm_kms_helper_is_poll_worker()) {
-		ret = pm_runtime_get_sync(connector->dev->dev);
+	if (drm_kms_helper_is_poll_worker()) {
+		pm_runtime_get_noresume(dev->dev);
+	} else {
+		ret = pm_runtime_get_sync(dev->dev);
 		if (ret < 0 && ret != -EACCES)
 			return conn_status;
 	}
@@ -329,10 +333,8 @@ detect_analog:
 
  out:
 
-	if (!drm_kms_helper_is_poll_worker()) {
-		pm_runtime_mark_last_busy(connector->dev->dev);
-		pm_runtime_put_autosuspend(connector->dev->dev);
-	}
+	pm_runtime_mark_last_busy(dev->dev);
+	pm_runtime_put_autosuspend(dev->dev);
 
 	return conn_status;
 }