drm/i915/dmc_wl: Check for non-zero refcount in release work

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>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241108130218.24125-5-gustavo.sousa@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dmc_wl.c b/drivers/gpu/drm/i915/display/intel_dmc_wl.c
index 9255505..a0a0607 100644 (file)
--- 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);