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Diffstat (limited to 'src/soc/intel/broadwell/igd.c')
-rw-r--r--src/soc/intel/broadwell/igd.c36
1 files changed, 28 insertions, 8 deletions
diff --git a/src/soc/intel/broadwell/igd.c b/src/soc/intel/broadwell/igd.c
index dab2d15750..f4322bf70e 100644
--- a/src/soc/intel/broadwell/igd.c
+++ b/src/soc/intel/broadwell/igd.c
@@ -335,14 +335,34 @@ static void igd_setup_panel(struct device *dev)
gtt_write(PCH_PP_DIVISOR, reg32);
}
- /* Enable Backlight if needed */
- if (conf->gpu_cpu_backlight) {
- gtt_write(BLC_PWM_CPU_CTL2, BLC_PWM2_ENABLE);
- gtt_write(BLC_PWM_CPU_CTL, conf->gpu_cpu_backlight);
- }
- if (conf->gpu_pch_backlight) {
- gtt_write(BLC_PWM_PCH_CTL1, BLM_PCH_PWM_ENABLE);
- gtt_write(BLC_PWM_PCH_CTL2, conf->gpu_pch_backlight);
+ /* So far all devices seem to use the PCH PWM function.
+ The CPU PWM registers are all zero after reset. */
+ if (conf->gpu_pch_backlight_pwm_hz) {
+ /* For Lynx Point-LP:
+ Reference clock is 24MHz. We can choose either a 16
+ or a 128 step increment. Use 16 if we would have less
+ than 100 steps otherwise. */
+ const unsigned int hz_limit = 24 * 1000 * 1000 / 128 / 100;
+ unsigned int pwm_increment, pwm_period;
+ u32 south_chicken2;
+
+ south_chicken2 = gtt_read(SOUTH_CHICKEN2);
+ if (conf->gpu_pch_backlight_pwm_hz > hz_limit) {
+ pwm_increment = 16;
+ south_chicken2 &= ~(1 << 5);
+ } else {
+ pwm_increment = 128;
+ south_chicken2 |= 1 << 5;
+ }
+ gtt_write(SOUTH_CHICKEN2, south_chicken2);
+
+ pwm_period = 24 * 1000 * 1000 / pwm_increment / conf->gpu_pch_backlight_pwm_hz;
+ /* Start with a 50% duty cycle. */
+ gtt_write(BLC_PWM_PCH_CTL2, pwm_period << 16 | pwm_period / 2);
+
+ gtt_write(BLC_PWM_PCH_CTL1,
+ (conf->gpu_pch_backlight_polarity == GPU_BACKLIGHT_POLARITY_LOW) << 29 |
+ BLM_PCH_OVERRIDE_ENABLE | BLM_PCH_PWM_ENABLE);
}
}