[Intel-gfx] [RFC 1/2] drm/i915/dp: optimize pps_lock wherever required

[Anshuman Gupta]

Reading backlight status from PPS register doesn't require
AUX power on the platform which has South Display Engine on PCH.
It invokes a unnecessary power well enable/disable noise.
optimize it wherever is possible.

Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 47 +++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 3896d08c4177..37371aa5f7c5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -892,6 +892,47 @@ pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
 	return 0;
 }
 
+/*
+ * Platform with PCH based SDE doesn't require to enable AUX power
+ * for simple PPS register access like whether backlight is enabled.
+ * use pch_pps_lock()/pch_pps_unlock() wherever we don't require
+ * aux power to avoid unnecessary power well enable/disable back
+ * and forth.
+ */
+static intel_wakeref_t
+pch_pps_lock(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	intel_wakeref_t wakeref;
+
+	if (!HAS_PCH_SPLIT(dev_priv))
+		wakeref = intel_display_power_get(dev_priv,
+						  intel_aux_power_domain(dp_to_dig_port(intel_dp)));
+	else
+		wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);
+
+	mutex_lock(&dev_priv->pps_mutex);
+
+	return wakeref;
+}
+
+static intel_wakeref_t
+pch_pps_unlock(struct intel_dp *intel_dp, intel_wakeref_t wakeref)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+
+	mutex_unlock(&dev_priv->pps_mutex);
+
+	if (!HAS_PCH_SPLIT(dev_priv))
+		intel_display_power_put(dev_priv,
+					intel_aux_power_domain(dp_to_dig_port(intel_dp)),
+					wakeref);
+	else
+		intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
+
+	return 0;
+}
+
 #define with_pps_lock(dp, wf) \
 	for ((wf) = pps_lock(dp); (wf); (wf) = pps_unlock((dp), (wf)))
 
@@ -3449,8 +3490,10 @@ static void intel_edp_backlight_power(struct intel_connector *connector,
 	bool is_enabled;
 
 	is_enabled = false;
-	with_pps_lock(intel_dp, wakeref)
-		is_enabled = ilk_get_pp_control(intel_dp) & EDP_BLC_ENABLE;
+	wakeref = pch_pps_lock(intel_dp);
+	is_enabled = ilk_get_pp_control(intel_dp) & EDP_BLC_ENABLE;
+	pch_pps_unlock(intel_dp, wakeref);
+
 	if (is_enabled == enable)
 		return;
 
-- 
2.26.2