[Intel-gfx] [PATCH] drm/i915/backlight: handle enabled but zero duty cycle at module load

[Jani Nikula]

Don't consider enabled but zero duty cycle backlight disabled. Clamp
level between min and max for sanity.

Signed-off-by: Jani Nikula <jani.nikula at intel.com>

---

Olof, does this work for you with i915.fastboot=1 (assuming that fails
on vanilla upstream)?
---
 drivers/gpu/drm/i915/intel_panel.c | 40 +++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 72183a057c79..e20eae76b8e8 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1473,10 +1473,11 @@ static int lpt_setup_backlight(struct intel_connector *connector, enum pipe unus
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
 	val = lpt_get_backlight(connector);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
-	panel->backlight.enabled = (pch_ctl1 & BLM_PCH_PWM_ENABLE) &&
-		panel->backlight.level != 0;
+	panel->backlight.enabled = pch_ctl1 & BLM_PCH_PWM_ENABLE;
 
 	return 0;
 }
@@ -1503,11 +1504,13 @@ static int pch_setup_backlight(struct intel_connector *connector, enum pipe unus
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
 	val = pch_get_backlight(connector);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
 	cpu_ctl2 = I915_READ(BLC_PWM_CPU_CTL2);
 	panel->backlight.enabled = (cpu_ctl2 & BLM_PWM_ENABLE) &&
-		(pch_ctl1 & BLM_PCH_PWM_ENABLE) && panel->backlight.level != 0;
+		(pch_ctl1 & BLM_PCH_PWM_ENABLE);
 
 	return 0;
 }
@@ -1543,9 +1546,11 @@ static int i9xx_setup_backlight(struct intel_connector *connector, enum pipe unu
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
 	val = i9xx_get_backlight(connector);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
-	panel->backlight.enabled = panel->backlight.level != 0;
+	panel->backlight.enabled = val != 0;
 
 	return 0;
 }
@@ -1576,10 +1581,11 @@ static int i965_setup_backlight(struct intel_connector *connector, enum pipe unu
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
 	val = i9xx_get_backlight(connector);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
-	panel->backlight.enabled = (ctl2 & BLM_PWM_ENABLE) &&
-		panel->backlight.level != 0;
+	panel->backlight.enabled = ctl2 & BLM_PWM_ENABLE;
 
 	return 0;
 }
@@ -1609,10 +1615,11 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe
 	panel->backlight.min = get_backlight_min_vbt(connector);
 
 	val = _vlv_get_backlight(dev, pipe);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
-	panel->backlight.enabled = (ctl2 & BLM_PWM_ENABLE) &&
-		panel->backlight.level != 0;
+	panel->backlight.enabled = ctl2 & BLM_PWM_ENABLE;
 
 	return 0;
 }
@@ -1655,10 +1662,11 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
 		return -ENODEV;
 
 	val = bxt_get_backlight(connector);
-	panel->backlight.level = intel_panel_compute_brightness(connector, val);
+	val = intel_panel_compute_brightness(connector, val);
+	panel->backlight.level = clamp(val, panel->backlight.min,
+				       panel->backlight.max);
 
-	panel->backlight.enabled = (pwm_ctl & BXT_BLC_PWM_ENABLE) &&
-		panel->backlight.level != 0;
+	panel->backlight.enabled = pwm_ctl & BXT_BLC_PWM_ENABLE;
 
 	return 0;
 }
-- 
2.1.4