[Intel-gfx] [PATCH 3/3] drm/i915/vlv: use min brightness from VBT

[Jesse Barnes]

Going below the minimum value may affect the BLC_EN line, so try to use
the VBT provided minimum where possible, otherwise use an experimentally
derived value to prevent the panel from coming up.

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_drv.h    |  1 +
 drivers/gpu/drm/i915/intel_bios.c  |  3 ++-
 drivers/gpu/drm/i915/intel_drv.h   |  1 +
 drivers/gpu/drm/i915/intel_panel.c | 10 +++++++++-
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ff02225..3c40dcb 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1148,6 +1148,7 @@ struct intel_vbt_data {
 	struct {
 		u16 pwm_freq_hz;
 		bool active_low_pwm;
+		u8 min_brightness;
 	} backlight;
 
 	/* MIPI DSI */
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 4867f4c..e8dedf5 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -301,11 +301,12 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 
 	dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
 	dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
+	dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
 	DRM_DEBUG_KMS("VBT backlight PWM modulation frequency %u Hz, "
 		      "active %s, min brightness %u, level %u\n",
 		      dev_priv->vbt.backlight.pwm_freq_hz,
 		      dev_priv->vbt.backlight.active_low_pwm ? "low" : "high",
-		      entry->min_brightness,
+		      dev_priv->vbt.backlight.min_brightness,
 		      backlight_data->level[panel_type]);
 }
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 0e91c40..053a968 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -166,6 +166,7 @@ struct intel_panel {
 		bool present;
 		u32 level;
 		u32 max;
+		u32 min;
 		bool enabled;
 		bool combination_mode;	/* gen 2/4 only */
 		bool active_low_pwm;
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 21c5e6f..27d7508 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -510,6 +510,9 @@ void intel_panel_set_backlight(struct intel_connector *connector, u32 level,
 	else
 		level = freq / max * level;
 
+	if (level < panel->backlight.min)
+		level = panel->backlight.min;
+
 	panel->backlight.level = level;
 	if (panel->backlight.device)
 		panel->backlight.device->props.brightness = level;
@@ -1047,7 +1050,12 @@ static int vlv_setup_backlight(struct intel_connector *connector)
 
 	ctl = I915_READ(VLV_BLC_PWM_CTL(PIPE_A));
 	panel->backlight.max = ctl >> 16;
-	if (!panel->backlight.max)
+	panel->backlight.min = dev_priv->vbt.backlight.min_brightness;
+	/* sane (i.e. checked on scope) default */
+	if (!panel->backlight.min)
+		panel->backlight.min = 64;
+	if (!panel->backlight.max ||
+	    panel->backlight.max < panel->backlight.min)
 		return -ENODEV;
 
 	val = _vlv_get_backlight(dev, PIPE_A);
-- 
1.8.4.2