[PATCH v3 04/18] drm/i915/dmc_wl: Check for non-zero refcount in release work

[Gustavo Sousa <gustavo.sousa@intel.com>]

When the DMC wakelock refcount reaches zero, we know that there are no
users and that we can do the actual release operation on the hardware,
which is queued with a delayed work. The idea of the delayed work is to
avoid performing the release if a new lock user appears (i.e. refcount
gets incremented) in a very short period of time.

Based on the above, the release work should bail out if refcount is
non-zero (meaning new lock users appeared in the meantime), but our
current code actually does the opposite: it bails when refcount is zero.
That means that the wakelock is not released when it should be; and
that, when the work is not canceled in time, it ends up being releasing
when it should not.

Fix that by inverting the condition.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dmc_wl.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dmc_wl.c b/drivers/gpu/drm/i915/display/intel_dmc_wl.c
index 9255505437d5..a0a060706305 100644
--- a/drivers/gpu/drm/i915/display/intel_dmc_wl.c
+++ b/drivers/gpu/drm/i915/display/intel_dmc_wl.c
@@ -76,8 +76,11 @@ static void intel_dmc_wl_work(struct work_struct *work)
 
 	spin_lock_irqsave(&wl->lock, flags);
 
-	/* Bail out if refcount reached zero while waiting for the spinlock */
-	if (!refcount_read(&wl->refcount))
+	/*
+	 * Bail out if refcount became non-zero while waiting for the spinlock,
+	 * meaning that the lock is now taken again.
+	 */
+	if (refcount_read(&wl->refcount))
 		goto out_unlock;
 
 	__intel_de_rmw_nowl(display, DMC_WAKELOCK1_CTL, DMC_WAKELOCK_CTL_REQ, 0);
-- 
2.47.0