On Mon, Apr 8, 2013 at 8:43 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: > On Mon, Apr 8, 2013 at 2:28 PM, Alex Deucher <alexdeucher at gmail.com> wrote: >> On Sat, Apr 6, 2013 at 12:05 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote: >>> When inlining the actual hpd output probing in >>> >>> commit 69787f7da6b2adc4054357a661aaa1701a9ca76f >>> Author: Daniel Vetter <daniel.vetter at ffwll.ch> >>> Date: Tue Oct 23 18:23:34 2012 +0000 >>> >>> drm: run the hpd irq event code directly >>> >>> the check for the drm_kms_hlper.poll module option was lost. This >>> regressed systems where this option is used to work-around output >>> probing issues (like irq storms). Restore the old behaviour. >> >> NAK. It's been a while since I looked at it, but the whole point of >> this patch set was to be able to disabling polling independently of >> hpd. If you add this check back, setting poll=0 disables both polling >> and hpd. I'd suggest we add a separate hpd option to disable hpd. > > The point for me was that the _driver_ can separate hpd handling from > polling. Which it still can with this patch applied. > > The issue at hand is that the old poll=0 also managed to paper over > some hpd handling irq storms and so breaking that is a regression. To > fix that we should imo apply this patch. > > We can revert this again once i915 has the hpd irq storm rate-limiting > stuff applied (presuming there's no other bug report for other > drivers). Also in 3.9 we have the reworked kms locking, so the usual > reason that polling causes cursor/pageflip stalls to set poll=0 > evaporated. So imo the only people who should still set poll=0 on 3.9 > are those with irq storms. And we've just broken that part ... There are also a lot of people that have non-HPD capable ports (usually old analog stuff like VGA) that they aren't using and they don't want to waste the CPU cycles polling them, but they still want hpd. I expect we'll get regression reports about the poll option getting broken again (hpd stops working with polling disabled, or monitor detection no longer works) if this patch is applied. Alex
