On Tue, Feb 21, 2012 at 01:37:37PM +0000, Daniel J Blueman wrote: > On 16 February 2012 13:07, Daniel Vetter <daniel at ffwll.ch> wrote: > > On Thu, Feb 16, 2012 at 11:44:46AM +0000, Daniel J Blueman wrote: > >> When charging Dell E5420 laptops, I see the Sandy Bridge South Display > >> Engine port C hotplug interrupt fire consistently at around 20Hz. Each > [] > >> Notably, when only using battery or only using AC, the port C > >> interrupts don't fire. It feels like the platform is using South > >> Display Port C for GPIO/I2C; setting the port C pulse duration from > >> 2ms to 100ms doesn't change the behaviour. I'll dump off the GPIO > >> settings, but what else is good to debug this? > > > > Yep, dumping the register state (intel_reg_dumper from intel-gpu-tools is > > handy for that) in the different situations sounds useful. > [] > > If this is indeed the bios we need to quirk this away. But I think we > > should check first whether we don't butcher something else accidently. > > When charging the battery, I see the SDE_PORTB_HOTPLUG, PORTC, PORTD > and SDE_AUX_MASK bits set (sometimes at different times) at ~20Hz > until the battery is charged, which is disconcerting. > > Hotplugging a HDMI cable, SDE_PORTB_HOTPLUG and SDE_AUX_MASK bits are > set once, so we can't mask these on this platform. > > Attached are the reg dumps. We see the backlight register > (BLC_PWM_CPU_CTL) and the A surface register (DSPASURF) vary across > multiple reads as expected. > > Any ideas? Nope, as in absolutely no idea. The only idea I have is that the expects us to do something with either acpi or opregion that we currently don't, but that's just handwaving. So I think you're left with filing a bug report with all the things you've gathered and hoping that we stumble over the missing piece of documentation :( -Daniel -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
