drm/i915/display: Add warn_on in intel_psr_pause()

Right now the only user of psr_pause/resume is intel_cdclk but
additional users will be added in the future and we may need
do reference counting for PSR pause and resume, for now only adding a
warn_on so this cases do not go unnoticed.

Cc: Mika Kahola <mika.kahola@intel.com>
Cc: Jouni Hogander <jouni.hogander@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211020003558.222198-2-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_psr.c

@@ -1346,6 +1346,7 @@ void intel_psr_disable(struct intel_dp *intel_dp,
  */
 void intel_psr_pause(struct intel_dp *intel_dp)
 {
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
 	struct intel_psr *psr = &intel_dp->psr;
 
 	if (!CAN_PSR(intel_dp))
@@ -1358,6 +1359,9 @@ void intel_psr_pause(struct intel_dp *intel_dp)
 		return;
 	}
 
+	/* If we ever hit this, we will need to add refcount to pause/resume */
+	drm_WARN_ON(&dev_priv->drm, psr->paused);
+
 	intel_psr_exit(intel_dp);
 	intel_psr_wait_exit_locked(intel_dp);
 	psr->paused = true;