Hi,
I want to use pwm brightness control over eDP DPCD register, however the capability registers read:
0x701 = 01
0x702 = 85
which according to the eDP specs means that DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP is set instead of DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP.
Chapter 8.3.2 of datasheet says that
"PWMO pin — the PWM signal generated by PTN3460 based on controls set in
DPCD registers. In addition, PTN3460 can pass through PWM signal from eDP
source as well. Please refer to Ref. 2 for more information."
However, Ref. 2 doesn't clarify this. It seems that PWM pass through is the default. How can I change that?
Regards,
Nikolaus Voss
Hi,
any update on this? How can I program the PWM via DPCD register?
Regards,
Nikolaus
Update: Writing PWM specs to DPCD-registers works, PTN3460 simply reports wrong capabilities.
Can PTN3460 be fixed to comply with eDP spec?
Hi Tomas,
thanks for your answer. So why is DPCD reg 0x702 set to 85 then? I use PTN3460 on linux along with the intel_dp_aux_backlight.c driver (part of i915 driver). It refuses to work with this register content as DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP is not set. How can this DPCD register be influenced? Are there any linux drivers known to work with brightness setting over AUX channel?
Regards,
Nikolaus