If the firmware did not initialize the backlight PWM registers, set up a
default PWM frequency of 200 Hz. This is determined using the following
formula:
freq = refclk / (128 * pwm_max)
The PWM register allows the max PWM value to be set. So we want to use
the formula, where freq = 200:
pwm_max = refclk / (128 * freq)
This patch will, in the case of missing PWM register initialization
values, look for the reference clock frequency. Based on that, it sets
an appropriate max PWM value for a frequency of 200 Hz.
If no refclk frequency is found, the max PWM will be zero, which results
in no change to the PWM registers.
Signed-off-by: Simon Que <s...@chromium.org>
---
drivers/gpu/drm/i915/i915_reg.h | 1 +
drivers/gpu/drm/i915/intel_panel.c | 37 +++++++++++++++++++++++++++++------
2 files changed, 31 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5d5def7..a832028 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3275,6 +3275,7 @@
#define PWM_POLARITY_ACTIVE_HIGH2 (0 << 28)
#define BLC_PWM_PCH_CTL2 0xc8254
+#define BLC_PWM_PCH_FREQ_SHIFT 16
#define PCH_PP_STATUS 0xc7200
#define PCH_PP_CONTROL 0xc7204
diff --git a/drivers/gpu/drm/i915/intel_panel.c
b/drivers/gpu/drm/i915/intel_panel.c
index f15388c..f865e52 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -32,6 +32,10 @@
#define PCI_LBPC 0xf4 /* legacy/combination backlight modes */
+/* For computing default PWM settings */
+#define DEFAULT_BACKLIGHT_PWM_FREQ 200
+#define BACKLIGHT_REFCLK_DIVISOR 128
+
void
intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
struct drm_display_mode *adjusted_mode)
@@ -129,12 +133,31 @@ static int is_backlight_combination_mode(struct
drm_device *dev)
return 0;
}
+static u32 i915_get_default_max_backlight(struct drm_i915_private *dev_priv)
+{
+ u32 refclk_freq_mhz = 0;
+ u32 max_pwm = 0;
+ if (HAS_PCH_SPLIT(dev_priv->dev))
+ refclk_freq_mhz = I915_READ(PCH_RAWCLK_FREQ) & RAWCLK_FREQ_MASK;
+ else if (dev_priv->lvds_use_ssc)
+ refclk_freq_mhz = dev_priv->lvds_ssc_freq;
+
+ max_pwm = refclk_freq_mhz * 1000000 /
+ (BACKLIGHT_REFCLK_DIVISOR * DEFAULT_BACKLIGHT_PWM_FREQ);
+
+ if (HAS_PCH_SPLIT(dev_priv->dev))
+ dev_priv->saveBLC_PWM_CTL2 = max_pwm << BLC_PWM_PCH_FREQ_SHIFT;
+ else
+ dev_priv->saveBLC_PWM_CTL = max_pwm <<
+ BACKLIGHT_MODULATION_FREQ_SHIFT;
+ return max_pwm;
+}
+
static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv)
{
u32 val;
- /* Restore the CTL value if it lost, e.g. GPU reset */
-
+ /* Restore the CTL value if it was lost, e.g. GPU reset */
if (HAS_PCH_SPLIT(dev_priv->dev)) {
val = I915_READ(BLC_PWM_PCH_CTL2);
if (dev_priv->saveBLC_PWM_CTL2 == 0) {
@@ -168,11 +191,11 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
max = i915_read_blc_pwm_ctl(dev_priv);
if (max == 0) {
- /* XXX add code here to query mode clock or hardware clock
- * and program max PWM appropriately.
- */
- printk_once(KERN_WARNING "fixme: max PWM is zero.\n");
- return 1;
+ /* If backlight PWM registers have not been set, set them to */
+ /* default backlight PWM settings. */
+ max = i915_get_default_max_backlight(dev_priv);
+ i915_read_blc_pwm_ctl(dev_priv);
+ return max;
}
if (HAS_PCH_SPLIT(dev)) {
--
1.7.2.3
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