drm/i915/backlight: setup and cache pwm alternate increment value

This will also be needed later on when setting up the alternate
increment in backlight enable.

Cc: Shawn Lee <shawn.c.lee@intel.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/9984b20bc59aee90b83caf59ce91f3fb122c9627.1474281249.git.jani.nikula@intel.com
(cherry picked from commit 32b421e79e6b546da1d469f1229403ac9142d695)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

2 files changed, 12 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 8fd16adf069b..c3e65e515c9d 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -263,6 +263,7 @@ struct intel_panel {
                 bool enabled;
                 bool combination_mode;  /* gen 2/4 only */
                 bool active_low_pwm;
+                bool alternate_pwm_increment;   /* lpt+ */
 
                 /* PWM chip */
                 bool util_pin_active_low;       /* bxt+ */
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index c10e9b0405e8..8bc43205d6a0 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1242,10 +1242,10 @@ static u32 bxt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
  */
 static u32 spt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
 {
-        struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
+        struct intel_panel *panel = &connector->panel;
         u32 mul;
 
-        if (I915_READ(SOUTH_CHICKEN1) & SPT_PWM_GRANULARITY)
+        if (panel->backlight.alternate_pwm_increment)
                 mul = 128;
         else
                 mul = 16;
@@ -1261,9 +1261,10 @@ static u32 spt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
 static u32 lpt_hz_to_pwm(struct intel_connector *connector, u32 pwm_freq_hz)
 {
         struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
+        struct intel_panel *panel = &connector->panel;
         u32 mul, clock;
 
-        if (I915_READ(SOUTH_CHICKEN2) & LPT_PWM_GRANULARITY)
+        if (panel->backlight.alternate_pwm_increment)
                 mul = 16;
         else
                 mul = 128;
@@ -1414,6 +1415,13 @@ static int lpt_setup_backlight(struct intel_connector *connector, enum pipe unus
         struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
         struct intel_panel *panel = &connector->panel;
         u32 pch_ctl1, pch_ctl2, val;
+        bool alt;
+
+        if (HAS_PCH_LPT(dev_priv))
+                alt = I915_READ(SOUTH_CHICKEN2) & LPT_PWM_GRANULARITY;
+        else
+                alt = I915_READ(SOUTH_CHICKEN1) & SPT_PWM_GRANULARITY;
+        panel->backlight.alternate_pwm_increment = alt;
 
         pch_ctl1 = I915_READ(BLC_PWM_PCH_CTL1);
         panel->backlight.active_low_pwm = pch_ctl1 & BLM_PCH_POLARITY;