On Wed, Jul 05, 2017 at 05:40:19PM +0300, David Weinehall wrote: > On Wed, Jul 05, 2017 at 01:03:46PM +0300, Jani Nikula wrote: > > On Tue, 04 Jul 2017, David Weinehall <david.weinehall@xxxxxxxxxxxxxxx> wrote: > > > This reverts commit ae25eceab616d16a07bcaa434b84463d58a3bdc3. > > > > > > The introduction of dynamic backlight control causes > > > Lenovo ThinkPad X1 Carbon 4th Gen to boot to a black screen; > > > presumably the backlight is off. > > > > Oh, I thought reverting just this commit was not enough for you, based > > on the previous discussion in the patch thread. If this is enough, and > > the DPCD backlight by default works for you, I might be inclined to go > > with just defaulting to false here. > > Yeah, that was indeed my experience, but I cannot reproduce that > behaviour now; disabling DBC seems to be enough to make things work. > It might be that I made some mistake in my earlier testing. > > I retested now, with the following results: > > Both DPCD & DBC enabled: black screen > DBC enabled, DPCD disabled: works > DBC disabled, DPCD enabled: works > DBC disabled, DPCD disabled: works > > Based on my understanding of the code, DPCD backlight is required for > DBC to work, so it makes sense that disabling either of the two > makes things work (hence I don't understand how I got my earlier > result where just disabling DBC wasn't enough). > > Anyhow, I'm fine with just changing the default to false. I need to NAK my own revert. It turns out that while booting with only i915.enable_dbc=0 gives backlight, the backlight will only work until a suspend/resume cycle has taken place; after that the display will come up blank, unless i915.enable_dpcd_backlight=0 is also passed. So I'll submit a new revert. Kind regards, David _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
