On Mon, Dec 21, 2015 at 04:14:53PM +0000, Chris Wilson wrote: > On Mon, Dec 21, 2015 at 05:02:08PM +0100, Daniel Vetter wrote: > > On Sat, Dec 19, 2015 at 09:58:43AM +0000, Chris Wilson wrote: > > > Once all the preparations are complete, we are ready to write the > > > modesetting to the hardware. During this phase, we will be making lots > > > of HW register access, so take a top level wakeref to prevent an > > > unwarranted rpm suspend cycle mid-commit. Lower level functions should > > > be waking the individual power wells as required. > > > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93439 > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > > Cc: Imre Deak <imre.deak@xxxxxxxxx> > > > > The original idea here was that doing this will paper over bugs in our rpm > > refcounting. There's also the problem that for modeset stuff we have all > > the power wells still to take care of. > > > > For the referenced bug we should add a power domain check in the get hw > > state function instead, which is what we've been doing with all the other > > similar hw state readout functions too. > > Agreed that there is another bug, but in the long term, we do want a > "prolonged" wakeref here. In the next evolution of the wakeref assertions, > we should be able to differentiate between the two (i.e. when we have > fine grained wakerefs around the hw access, we need to assert we hold one > of that type in the mmio accessor, rather than the prolonged version). Why? If we enforce that I fear we lose implicit coverage. Currently if you touch any piece of modeset hw and don't have the corresponding long-time rpm/power well ref there's a good chance something will spot this. If we have a short-term rpm reference for everything we won't noticed these problems around the long-term rpm references any more. Imo the only thing short-term references are useful for is lockdep annotations to detect deadlocks, since lockdep requires that we drop a lock in the same process again. Long-term ones would simply do a might_lock in the get function to annotate the deadlock with rpm resume functions. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
