On Tue, Apr 05, 2016 at 06:01:54PM -0400, Lyude wrote: > Hi. Currently I'm working on a bug in the i915 driver where hotplugging seems to > break if we power on the machine without any connectors attached: > > https://bugzilla.redhat.com/show_bug.cgi?id=1277863 > > So the main cause of the issue seems to be that we're not keeping the right > power wells on for HPD to work. Booting with say, HDMI, seems to result in the > POWER_DOMAIN_AUDIO domain getting ref'd (even when it's unplugged, which seems > to be another bug in the driver I've seen on a few systems at this point), which > stops the entire display domain from being shut off and subsequently keeps hpd > working. Without anything plugged in nothing turns on any power wells and the > hpd is non-functional. > > Of course my first thought was to just keep the power wells required for HPD on > for as long as we have HPD enabled in the driver. I'm not entirely sure of how > this can be done though, as disabling hotplugging interrupts is done in a > context where IRQs are disabled and as such it's impossible to grab a reference > to the power domain we need since that requires us to grab a mutex. I don't see > any pre/post uninstall hooks for this either, so just having the power well > turned on and off whenever hpd is toggled doesn't seem very easy. > > On top of this, after talking to a few coworkers I'm not sure if holding a power > ref as long as hpd interrupts are enabled is the right solution either, since it > could be costly in terms of power usage. He suggested that I enable polling for > each connector in the situation where all the power domains are disabled, but > having hotplugging disabled doesn't sound right to me either. > > So I guess my questions are: > 1. Should we be falling back to polling when the required power wells for > hotplug detection aren't enabled, instead of keeping them enabled to make > hotplugging work? > 2. If polling isn't the right way to go, what is the best way to go about > keeping a ref to the required power wells and dropping it whenever > hotplugging is disabled? See https://bugs.freedesktop.org/show_bug.cgi?id=89008 for the discussion on different options. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
