On Tue, Aug 26, 2014 at 04:15:53PM +0000, Scot Doyle wrote: > On Tue, 26 Aug 2014, Daniel Vetter wrote: > > On Thu, Aug 21, 2014 at 07:12:59AM +0000, Scot Doyle wrote: > >> When we enter intel_modeset_setup_hw_state during resume > >> - BLC_PWM_CPU_CTL2 == BLM_PWM_ENABLE > >> - the physical backlight is off > > > > Hm, this is actually interesting - we have some other evidence that the > > best way to shut off the backlight is actually to just set the pwm duty > > cycle to 0. Can you please check that this is the case for your system? > > /sys/class/backlight/intel_backlight/brightness > 0 -> backlight not visible > 1 -> backlight visible > 937 -> max backlight > > Setting /sys/class/backlight/intel_backlight/brightness to 0 updates > BLC_PWM_CPU_CTL, but BLC_PWM_CPU_CTL2 remains 0xe0000000. > > > > Maybe we just need to extend the check to look for !PWM_ENABLE || > > duty_cycle == 0. > > The following measurements hold true no matter the duty cycle before > suspend: > > When entering hsw_enable_pc8 during suspend > - the physical backlight is off > - BLC_PWM_CPU_CTL == 0x3a900000 (BACKLIGHT_DUTY_CYCLE_MASK == ffff) > - BLC_PWM_CPU_CTL2 == 0x60000000 (BLM_PWM_ENABLE) > > When exiting hsw_disable_pc8 during resume > - the physical backlight is off > - BLC_PWM_CPU_CTL == 0x200 > - BLC_PWM_CPU_CTL2 == 0x80000000 (BLM_PWM_ENABLE | BLM_TRANSCODER_EDP) > > When entering pch_enable_backlight during resume > - the physical backlight is off > - BLC_PWM_CPU_CTL == 0x200 > - BLC_PWM_CPU_CTL2 == 0x80000000 (BLM_PWM_ENABLE) > > When exiting pch_enable_backlight during resume > - the physical backlight is off > - BLC_PWM_CPU_CTL == duty cycle prior to suspend > - BLC_PWM_CPU_CTL2 == 0xe0000000 (BLM_PWM_ENABLE | BLM_TRANSCODER_EDP) > > > So the BIOS is setting BLC_PWM_CPU_CTL=0x200 and BLC_PWM_CPU_CTL2=0x80000000 ? Indeed the bios seems to just but gunk into that register. And if we add in all the knobs there's piles of them (you have semi-duplicated backlight registers on hsw on the PCH), so I guess it doesn't make sense to combine them all and warn if something goes awry, at least not in a -fixes patch. So Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> on your original patch. Jani can decide whether he wants to save this WARN_ON (imo it's useful to have such sanity-checks) in -next by taking all the various bits and duty cycles into account. But maybe just on the latest platforms, that still should give is good coverage, but with a lot less fuss. Thanks for tracking this all down. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
