linux-kernel - [PATCH 4/9] drm/nouveau/kms/fbcon: Fix pm_runtime calls in nouveau_fbcon_output_poll

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Date:   Wed, 29 Jul 2020 17:36:58 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     nouveau@...ts.freedesktop.org
Cc:     stable@...r.kernel.org, Ben Skeggs <bskeggs@...hat.com>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Karol Herbst <kherbst@...hat.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH 4/9] drm/nouveau/kms/fbcon: Fix pm_runtime calls in nouveau_fbcon_output_poll_changed()

Noticed two problems here:
* We're not dropping our runtime PM refs after getting an error
* We're not backing off when pm_runtime_get() indicates that there's
  already a resume in progress (-EINPROGRESS) (after which any delayed
  fbcon events will get handled anyway)

So, let's fix those.

Signed-off-by: Lyude Paul <lyude@...hat.com>
Fixes: 7fec8f5379fb ("drm/nouveau/drm/nouveau: Fix deadlock with fb_helper with async RPM requests")
Cc: stable@...r.kernel.org
Cc: Ben Skeggs <bskeggs@...hat.com>
Cc: dri-devel@...ts.freedesktop.org
Cc: nouveau@...ts.freedesktop.org
Cc: <stable@...r.kernel.org> # v4.19+
---
 drivers/gpu/drm/nouveau/nouveau_fbcon.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index 4d9f3b5ae72d2..b936bf1c14dec 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -503,10 +503,7 @@ nouveau_fbcon_output_poll_changed(struct drm_device *dev)
 	ret = pm_runtime_get(dev->dev);
 	if (ret == 1 || ret == -EACCES) {
 		drm_fb_helper_hotplug_event(&fbcon->helper);
-
-		pm_runtime_mark_last_busy(dev->dev);
-		pm_runtime_put_autosuspend(dev->dev);
-	} else if (ret == 0) {
+	} else if (ret == 0 || ret == -EINPROGRESS) {
 		/* If the GPU was already in the process of suspending before
 		 * this event happened, then we can't block here as we'll
 		 * deadlock the runtime pmops since they wait for us to
@@ -516,11 +513,15 @@ nouveau_fbcon_output_poll_changed(struct drm_device *dev)
 		NV_DEBUG(drm, "fbcon HPD event deferred until runtime resume\n");
 		fbcon->hotplug_waiting = true;
 		pm_runtime_put_noidle(drm->dev->dev);
+		goto out;
 	} else {
 		DRM_WARN("fbcon HPD event lost due to RPM failure: %d\n",
 			 ret);
 	}
 
+	pm_runtime_mark_last_busy(dev->dev);
+	pm_runtime_put_autosuspend(dev->dev);
+out:
 	mutex_unlock(&fbcon->hotplug_lock);
 }
 
-- 
2.26.2