drm/i915: Refactor panel backlight controls

There were two instances of code to control the panel backlight and
neither handled the complete set of device variations.

Fixes:

  Bug 29716 - [GM965] Regression: Backlight resets to minimum when changing resolution
  https://bugs.freedesktop.org/show_bug.cgi?id=29716

And a bug on one of my PineView boxes which overflowed the backlight
value.

Incorporates part of a similar patch by Matthew Garrett that exposes a
native Intel backlight controller.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_drv.h

@@ -319,7 +319,7 @@ typedef struct drm_i915_private {
 	struct intel_overlay *overlay;
 
 	/* LVDS info */
-	int backlight_duty_cycle;  /* restore backlight to this value */
+	int backlight_level;  /* restore backlight to this value */
 	bool panel_wants_dither;
 	struct drm_display_mode *panel_fixed_mode;
 	struct drm_display_mode *lfp_lvds_vbt_mode; /* if any */

drivers/gpu/drm/i915/intel_drv.h

@@ -204,13 +204,16 @@ extern bool intel_pch_has_edp(struct drm_crtc *crtc);
 extern bool intel_dpd_is_edp(struct drm_device *dev);
 extern void intel_edp_link_config (struct intel_encoder *, int *, int *);
 
-
+/* intel_panel.c */
 extern void intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
 				   struct drm_display_mode *adjusted_mode);
 extern void intel_pch_panel_fitting(struct drm_device *dev,
 				    int fitting_mode,
 				    struct drm_display_mode *mode,
 				    struct drm_display_mode *adjusted_mode);
+extern u32 intel_panel_get_max_backlight(struct drm_device *dev);
+extern u32 intel_panel_get_backlight(struct drm_device *dev);
+extern void intel_panel_set_backlight(struct drm_device *dev, u32 level);
 
 extern int intel_panel_fitter_pipe (struct drm_device *dev);
 extern void intel_crtc_load_lut(struct drm_crtc *crtc);

drivers/gpu/drm/i915/intel_lvds.c

@@ -53,43 +53,6 @@ static struct intel_lvds *enc_to_intel_lvds(struct drm_encoder *encoder)
 	return container_of(enc_to_intel_encoder(encoder), struct intel_lvds, base);
 }
 
-/**
- * Sets the backlight level.
- *
- * \param level backlight level, from 0 to intel_lvds_get_max_backlight().
- */
-static void intel_lvds_set_backlight(struct drm_device *dev, int level)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 blc_pwm_ctl, reg;
-
-	if (HAS_PCH_SPLIT(dev))
-		reg = BLC_PWM_CPU_CTL;
-	else
-		reg = BLC_PWM_CTL;
-
-	blc_pwm_ctl = I915_READ(reg) & ~BACKLIGHT_DUTY_CYCLE_MASK;
-	I915_WRITE(reg, (blc_pwm_ctl |
-				 (level << BACKLIGHT_DUTY_CYCLE_SHIFT)));
-}
-
-/**
- * Returns the maximum level of the backlight duty cycle field.
- */
-static u32 intel_lvds_get_max_backlight(struct drm_device *dev)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 reg;
-
-	if (HAS_PCH_SPLIT(dev))
-		reg = BLC_PWM_PCH_CTL2;
-	else
-		reg = BLC_PWM_CTL;
-
-	return ((I915_READ(reg) & BACKLIGHT_MODULATION_FREQ_MASK) >>
-		BACKLIGHT_MODULATION_FREQ_SHIFT) * 2;
-}
-
 /**
  * Sets the power state for the panel.
  */
@@ -117,9 +80,9 @@ static void intel_lvds_set_power(struct drm_device *dev, bool on)
 		if (wait_for(I915_READ(status_reg) & PP_ON, 1000))
 			DRM_ERROR("timed out waiting to enable LVDS pipe");
 
-		intel_lvds_set_backlight(dev, dev_priv->backlight_duty_cycle);
+		intel_panel_set_backlight(dev, dev_priv->backlight_level);
 	} else {
-		intel_lvds_set_backlight(dev, 0);
+		intel_panel_set_backlight(dev, 0);
 
 		I915_WRITE(ctl_reg, I915_READ(ctl_reg) &
 			   ~POWER_TARGET_ON);
@@ -386,16 +349,8 @@ static void intel_lvds_prepare(struct drm_encoder *encoder)
 {
 	struct drm_device *dev = encoder->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 reg;
-
-	if (HAS_PCH_SPLIT(dev))
-		reg = BLC_PWM_CPU_CTL;
-	else
-		reg = BLC_PWM_CTL;
 
-	dev_priv->saveBLC_PWM_CTL = I915_READ(reg);
-	dev_priv->backlight_duty_cycle = (dev_priv->saveBLC_PWM_CTL &
-				       BACKLIGHT_DUTY_CYCLE_MASK);
+	dev_priv->backlight_level = intel_panel_get_backlight(dev);
 
 	intel_lvds_set_power(dev, false);
 }
@@ -405,9 +360,8 @@ static void intel_lvds_commit( struct drm_encoder *encoder)
 	struct drm_device *dev = encoder->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (dev_priv->backlight_duty_cycle == 0)
-		dev_priv->backlight_duty_cycle =
-			intel_lvds_get_max_backlight(dev);
+	if (dev_priv->backlight_level == 0)
+		dev_priv->backlight_level = intel_panel_get_max_backlight(dev);
 
 	intel_lvds_set_power(dev, true);
 }

drivers/gpu/drm/i915/intel_opregion.c

@@ -31,9 +31,9 @@
 #include "drmP.h"
 #include "i915_drm.h"
 #include "i915_drv.h"
+#include "intel_drv.h"
 
 #define PCI_ASLE 0xe4
-#define PCI_LBPC 0xf4
 #define PCI_ASLS 0xfc
 
 #define OPREGION_HEADER_OFFSET 0
@@ -147,36 +147,17 @@ static u32 asle_set_backlight(struct drm_device *dev, u32 bclp)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct opregion_asle *asle = dev_priv->opregion.asle;
-	u32 blc_pwm_ctl, blc_pwm_ctl2;
-	u32 max_backlight, level, shift;
+	u32 max;
 
 	if (!(bclp & ASLE_BCLP_VALID))
 		return ASLE_BACKLIGHT_FAILED;
 
 	bclp &= ASLE_BCLP_MSK;
-	if (bclp < 0 || bclp > 255)
+	if (bclp > 255)
 		return ASLE_BACKLIGHT_FAILED;
 
-	blc_pwm_ctl = I915_READ(BLC_PWM_CTL);
-	blc_pwm_ctl2 = I915_READ(BLC_PWM_CTL2);
-
-	if (IS_I965G(dev) && (blc_pwm_ctl2 & BLM_COMBINATION_MODE))
-		pci_write_config_dword(dev->pdev, PCI_LBPC, bclp);
-	else {
-		if (IS_PINEVIEW(dev)) {
-			blc_pwm_ctl &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);
-			max_backlight = (blc_pwm_ctl & BACKLIGHT_MODULATION_FREQ_MASK) >> 
-					BACKLIGHT_MODULATION_FREQ_SHIFT;
-			shift = BACKLIGHT_DUTY_CYCLE_SHIFT + 1;
-		} else {
-			blc_pwm_ctl &= ~BACKLIGHT_DUTY_CYCLE_MASK;
-			max_backlight = ((blc_pwm_ctl & BACKLIGHT_MODULATION_FREQ_MASK) >> 
-					BACKLIGHT_MODULATION_FREQ_SHIFT) * 2;
-			shift = BACKLIGHT_DUTY_CYCLE_SHIFT;
-		}
-		level = (bclp * max_backlight) / 255;
-		I915_WRITE(BLC_PWM_CTL, blc_pwm_ctl | (level << shift));
-	}
+	max = intel_panel_get_max_backlight(dev);
+	intel_panel_set_backlight(dev, bclp * max / 255);
 	asle->cblv = (bclp*0x64)/0xff | ASLE_CBLV_VALID;
 
 	return 0;
@@ -243,36 +224,6 @@ void intel_opregion_asle_intr(struct drm_device *dev)
 	asle->aslc = asle_stat;
 }
 
-static u32 asle_set_backlight_ironlake(struct drm_device *dev, u32 bclp)
-{
-	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct opregion_asle *asle = dev_priv->opregion.asle;
-	u32 cpu_pwm_ctl, pch_pwm_ctl2;
-	u32 max_backlight, level;
-
-	if (!(bclp & ASLE_BCLP_VALID))
-		return ASLE_BACKLIGHT_FAILED;
-
-	bclp &= ASLE_BCLP_MSK;
-	if (bclp < 0 || bclp > 255)
-		return ASLE_BACKLIGHT_FAILED;
-
-	cpu_pwm_ctl = I915_READ(BLC_PWM_CPU_CTL);
-	pch_pwm_ctl2 = I915_READ(BLC_PWM_PCH_CTL2);
-	/* get the max PWM frequency */
-	max_backlight = (pch_pwm_ctl2 >> 16) & BACKLIGHT_DUTY_CYCLE_MASK;
-	/* calculate the expected PMW frequency */
-	level = (bclp * max_backlight) / 255;
-	/* reserve the high 16 bits */
-	cpu_pwm_ctl &= ~(BACKLIGHT_DUTY_CYCLE_MASK);
-	/* write the updated PWM frequency */
-	I915_WRITE(BLC_PWM_CPU_CTL, cpu_pwm_ctl | level);
-
-	asle->cblv = (bclp*0x64)/0xff | ASLE_CBLV_VALID;
-
-	return 0;
-}
-
 /* Only present on Ironlake+ */
 void intel_opregion_gse_intr(struct drm_device *dev)
 {
@@ -297,7 +248,7 @@ void intel_opregion_gse_intr(struct drm_device *dev)
 	}
 
 	if (asle_req & ASLE_SET_BACKLIGHT)
-		asle_stat |= asle_set_backlight_ironlake(dev, asle->bclp);
+		asle_stat |= asle_set_backlight(dev, asle->bclp);
 
 	if (asle_req & ASLE_SET_PFIT) {
 		DRM_DEBUG_DRIVER("Pfit is not supported\n");

drivers/gpu/drm/i915/intel_panel.c

@@ -30,6 +30,8 @@
 
 #include "intel_drv.h"
 
+#define PCI_LBPC 0xf4 /* legacy/combination backlight modes */
+
 void
 intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
 		       struct drm_display_mode *adjusted_mode)
@@ -109,3 +111,110 @@ intel_pch_panel_fitting(struct drm_device *dev,
 	dev_priv->pch_pf_pos = (x << 16) | y;
 	dev_priv->pch_pf_size = (width << 16) | height;
 }
+
+static int is_backlight_combination_mode(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (IS_I965G(dev))
+		return I915_READ(BLC_PWM_CTL2) & BLM_COMBINATION_MODE;
+
+	if (IS_GEN2(dev))
+		return I915_READ(BLC_PWM_CTL) & BLM_LEGACY_MODE;
+
+	return 0;
+}
+
+u32 intel_panel_get_max_backlight(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 max;
+
+	if (HAS_PCH_SPLIT(dev)) {
+		max = I915_READ(BLC_PWM_PCH_CTL2) >> 16;
+	} else {
+		max = I915_READ(BLC_PWM_CTL);
+		if (IS_PINEVIEW(dev)) {
+			max >>= 17;
+		} else {
+			max >>= 16;
+			if (!IS_I965G(dev))
+				max &= ~1;
+		}
+
+		if (is_backlight_combination_mode(dev))
+			max *= 0xff;
+	}
+
+	if (max == 0) {
+		/* XXX add code here to query mode clock or hardware clock
+		 * and program max PWM appropriately.
+		 */
+		DRM_ERROR("fixme: max PWM is zero.\n");
+		max = 1;
+	}
+
+	DRM_DEBUG_DRIVER("max backlight PWM = %d\n", max);
+	return max;
+}
+
+u32 intel_panel_get_backlight(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 val;
+
+	if (HAS_PCH_SPLIT(dev)) {
+		val = I915_READ(BLC_PWM_CPU_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
+	} else {
+		val = I915_READ(BLC_PWM_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
+		if (IS_PINEVIEW(dev))
+			val >>= 1;
+
+		if (is_backlight_combination_mode(dev)){
+			u8 lbpc;
+
+			val &= ~1;
+			pci_read_config_byte(dev->pdev, PCI_LBPC, &lbpc);
+			val *= lbpc;
+			val >>= 1;
+		}
+	}
+
+	DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val);
+	return val;
+}
+
+static void intel_pch_panel_set_backlight(struct drm_device *dev, u32 level)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 val = I915_READ(BLC_PWM_CPU_CTL) & ~BACKLIGHT_DUTY_CYCLE_MASK;
+	I915_WRITE(BLC_PWM_CPU_CTL, val | level);
+}
+
+void intel_panel_set_backlight(struct drm_device *dev, u32 level)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 tmp;
+
+	DRM_DEBUG_DRIVER("set backlight PWM = %d\n", level);
+
+	if (HAS_PCH_SPLIT(dev))
+		return intel_pch_panel_set_backlight(dev, level);
+
+	if (is_backlight_combination_mode(dev)){
+		u32 max = intel_panel_get_max_backlight(dev);
+		u8 lpbc;
+
+		lpbc = level * 0xfe / max + 1;
+		level /= lpbc;
+		pci_write_config_byte(dev->pdev, PCI_LBPC, lpbc);
+	}
+
+	tmp = I915_READ(BLC_PWM_CTL);
+	if (IS_PINEVIEW(dev)) {
+		tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);
+		level <<= 1;
+	} else
+		tmp &= ~BACKLIGHT_DUTY_CYCLE_MASK;
+	I915_WRITE(BLC_PWM_CTL, tmp | level);
+}