drm/i915: do not access BLC_PWM_CTL2 on pre-gen4 hardware

The BLC_PWM_CTL2 register does not exist before gen4. While at it, do a
slight drive by cleanup of the code.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index c758ad277473..bee8cb6108a7 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -130,8 +130,9 @@ static int is_backlight_combination_mode(struct drm_device *dev)
         return 0;
 }
 
-static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
+static u32 i915_read_blc_pwm_ctl(struct drm_device *dev)
 {
+        struct drm_i915_private *dev_priv = dev->dev_private;
         u32 val;
 
         /* Restore the CTL value if it lost, e.g. GPU reset */
@@ -141,21 +142,22 @@ static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
                 if (dev_priv->regfile.saveBLC_PWM_CTL2 == 0) {
                         dev_priv->regfile.saveBLC_PWM_CTL2 = val;
                 } else if (val == 0) {
-                        I915_WRITE(BLC_PWM_PCH_CTL2,
-                                   dev_priv->regfile.saveBLC_PWM_CTL2);
                         val = dev_priv->regfile.saveBLC_PWM_CTL2;
+                        I915_WRITE(BLC_PWM_PCH_CTL2, val);
                 }
         } else {
                 val = I915_READ(BLC_PWM_CTL);
                 if (dev_priv->regfile.saveBLC_PWM_CTL == 0) {
                         dev_priv->regfile.saveBLC_PWM_CTL = val;
-                        dev_priv->regfile.saveBLC_PWM_CTL2 = I915_READ(BLC_PWM_CTL2);
+                        if (INTEL_INFO(dev)->gen >= 4)
+                                dev_priv->regfile.saveBLC_PWM_CTL2 =
+                                        I915_READ(BLC_PWM_CTL2);
                 } else if (val == 0) {
-                        I915_WRITE(BLC_PWM_CTL,
-                                   dev_priv->regfile.saveBLC_PWM_CTL);
-                        I915_WRITE(BLC_PWM_CTL2,
-                                   dev_priv->regfile.saveBLC_PWM_CTL2);
                         val = dev_priv->regfile.saveBLC_PWM_CTL;
+                        I915_WRITE(BLC_PWM_CTL, val);
+                        if (INTEL_INFO(dev)->gen >= 4)
+                                I915_WRITE(BLC_PWM_CTL2,
+                                           dev_priv->regfile.saveBLC_PWM_CTL2);
                 }
         }
 
@@ -164,10 +166,9 @@ static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
 
 static u32 _intel_panel_get_max_backlight(struct drm_device *dev)
 {
-        struct drm_i915_private *dev_priv = dev->dev_private;
         u32 max;
 
-        max = i915_read_blc_pwm_ctl(dev_priv);
+        max = i915_read_blc_pwm_ctl(dev);
 
         if (HAS_PCH_SPLIT(dev)) {
                 max >>= 16;