[PATCH] drm/nouveau: fix autosuspend cleanup during teardown

[Guangshuo Li <lgs201920130244@gmail.com>]

nouveau_drm_device_init() calls pm_runtime_use_autosuspend(), but
nouveau_drm_device_fini() does not call the matching
pm_runtime_dont_use_autosuspend().

If the autosuspend delay is set to a negative value while autosuspend
is enabled, the runtime PM core increments usage_count to prevent
runtime suspend. Without calling pm_runtime_dont_use_autosuspend()
during teardown, this reference is not dropped and usage_count remains
unbalanced.

The documentation for pm_runtime_use_autosuspend() also notes that it
is important to undo it with pm_runtime_dont_use_autosuspend() at
driver exit time, unless runtime PM was initially enabled with
devm_pm_runtime_enable().

Add the missing pm_runtime_dont_use_autosuspend() call to the common
device teardown path.

This issue was found by manual code inspection.

Fixes: 5addcf0a5f0f ("nouveau: add runtime PM support (v0.9)")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_drm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index e16f59b00f6f..1579a4b0785e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -585,6 +585,7 @@ nouveau_drm_device_fini(struct nouveau_drm *drm)
 	if (nouveau_pmops_runtime()) {
 		pm_runtime_get_sync(dev->dev);
 		pm_runtime_forbid(dev->dev);
+		pm_runtime_dont_use_autosuspend(dev->dev);
 	}
 
 	nouveau_led_fini(dev);
-- 
2.43.0