[PATCH v4 15/16] drm/i915: panel: Honor the VBT PWM min setting for devs with an external PWM controller

[Hans de Goede <hdegoede@redhat.com>]

So far for devices using an external PWM controller (devices using
pwm_setup_backlight()), we have been hardcoding the minimum allowed
PWM level to 0. But several of these devices specify a non 0 minimum
setting in their VBT.

Change pwm_setup_backlight() to use get_backlight_min_vbt() to get
the minimum level.

Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/i915/display/intel_panel.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 14e611c92194..cb28b9908ca4 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -1925,8 +1925,8 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 	 */
 	pwm_apply_args(panel->backlight.pwm);
 
-	panel->backlight.min = 0; /* 0% */
 	panel->backlight.max = 100; /* 100% */
+	panel->backlight.min = get_backlight_min_vbt(connector);
 	level = intel_panel_compute_brightness(connector, 100);
 	ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);
 
@@ -1941,8 +1941,9 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 
 	level = DIV_ROUND_UP(pwm_get_duty_cycle(panel->backlight.pwm) * 100,
 			     panel->backlight.pwm_period_ns);
-	panel->backlight.level =
-		intel_panel_compute_brightness(connector, level);
+	level = intel_panel_compute_brightness(connector, level);
+	panel->backlight.level = clamp(level, panel->backlight.min,
+				       panel->backlight.max);
 	panel->backlight.enabled = panel->backlight.level != 0;
 
 	drm_info(&dev_priv->drm, "Using %s PWM for LCD backlight control\n",
-- 
2.26.2