On Thu, 3 Feb 2011 16:30:56 -0800, Linus Torvalds <torvalds at linux-foundation.org> wrote: > On Thu, Feb 3, 2011 at 4:06 PM, Dave Airlie <airlied at gmail.com> wrote: > > > > If we are setting a mode on a connector it automatically will end up > > in a DPMS on state, > > so this seemed correct from what I can see. > > The more I look at that function, the more I disagree with you and > with that patch. > > The code is just crazy. > > First off, it isn't even necessarily setting a mode to begin with, > because as far as I can tell. If the mode doesn't change, neither > mode_changed nor fb_changed will be true, afaik. There seems to be a > fair amount of code there explicitly to avoid changing modes if not > necessary. > > But even _if_ we are setting a mode, if I read the code correctly, the > mode may be set to NULL - which seems to mean "turn it off". In which > case it looks to me that drm_helper_disable_unused_functions() will > actually do a > > (*crtc_funcs->dpms)(crtc, DRM_MODE_DPMS_OFF); > > call on the crtc in question. So then blindly just saying "it's mode > DRM_MODE_DPMS_ON" afterwards looks rather bogus to me. > > _Maybe_ it would work if it was done before that whole > "disable_unused" logic. Or maybe it should just be done in > drm_crtc_helper_set_mode(), which is what actually sets the mode (but > there's the 'fb_changed' case too) > > > A future mode set shouldn't ever not turn the connector on, since > > modesetting is an implicit > > DPMS, > > > > It sounds like something more subtle than that, though I'm happy to > > revert this for now, and let Keith > > think about it a bit more. > > So I haven't heard anything from Keith. Keith? Just revert it? Or do > you have a patch for people to try?
The goal is to make it so that when you *do* set a mode, DPMS gets set to ON (as the monitor will actually be "on" at that point). Here's a patch which does the DPMS_ON precisely when setting a mode. Dave thinks we should instead force dpms to match crtc->enabled, I'd rather have dpms get set when we know the hardware has been changed. (note, this patch compiles, but is otherwise only lightly tested).
