drm/i915: Add comments explaining the vdd on/off functions
Jani wanted some comments to explain why we call certain vdd on/off
functions in certain places.
v2: Make the comments more thorough (Imre)
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 0d468e6..97c5a0d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1354,6 +1354,11 @@
return control;
}
+/*
+ * Must be paired with edp_panel_vdd_off().
+ * Must hold pps_mutex around the whole on/off sequence.
+ * Can be nested with intel_edp_panel_vdd_{on,off}() calls.
+ */
static bool edp_panel_vdd_on(struct intel_dp *intel_dp)
{
struct drm_device *dev = intel_dp_to_dev(intel_dp);
@@ -1404,6 +1409,13 @@
return need_to_disable;
}
+/*
+ * Must be paired with intel_edp_panel_vdd_off() or
+ * intel_edp_panel_off().
+ * Nested calls to these functions are not allowed since
+ * we drop the lock. Caller must use some higher level
+ * locking to prevent nested calls from other threads.
+ */
void intel_edp_panel_vdd_on(struct intel_dp *intel_dp)
{
bool vdd;
@@ -1482,6 +1494,11 @@
schedule_delayed_work(&intel_dp->panel_vdd_work, delay);
}
+/*
+ * Must be paired with edp_panel_vdd_on().
+ * Must hold pps_mutex around the whole on/off sequence.
+ * Can be nested with intel_edp_panel_vdd_{on,off}() calls.
+ */
static void edp_panel_vdd_off(struct intel_dp *intel_dp, bool sync)
{
struct drm_i915_private *dev_priv =
@@ -1502,6 +1519,12 @@
edp_panel_vdd_schedule_off(intel_dp);
}
+/*
+ * Must be paired with intel_edp_panel_vdd_on().
+ * Nested calls to these functions are not allowed since
+ * we drop the lock. Caller must use some higher level
+ * locking to prevent nested calls from other threads.
+ */
static void intel_edp_panel_vdd_off(struct intel_dp *intel_dp, bool sync)
{
if (!is_edp(intel_dp))
@@ -4373,6 +4396,10 @@
drm_encoder_cleanup(encoder);
if (is_edp(intel_dp)) {
cancel_delayed_work_sync(&intel_dp->panel_vdd_work);
+ /*
+ * vdd might still be enabled do to the delayed vdd off.
+ * Make sure vdd is actually turned off here.
+ */
pps_lock(intel_dp);
edp_panel_vdd_off_sync(intel_dp);
pps_unlock(intel_dp);
@@ -4392,6 +4419,10 @@
if (!is_edp(intel_dp))
return;
+ /*
+ * vdd might still be enabled do to the delayed vdd off.
+ * Make sure vdd is actually turned off here.
+ */
pps_lock(intel_dp);
edp_panel_vdd_off_sync(intel_dp);
pps_unlock(intel_dp);
@@ -5095,6 +5126,10 @@
drm_dp_aux_unregister(&intel_dp->aux);
if (is_edp(intel_dp)) {
cancel_delayed_work_sync(&intel_dp->panel_vdd_work);
+ /*
+ * vdd might still be enabled do to the delayed vdd off.
+ * Make sure vdd is actually turned off here.
+ */
pps_lock(intel_dp);
edp_panel_vdd_off_sync(intel_dp);
pps_unlock(intel_dp);