On Wed, 2019-05-15 at 06:43 +0100, Tvrtko Ursulin wrote: > On 15/05/2019 01:06, Rodrigo Vivi wrote: > > On Tue, May 14, 2019 at 06:32:01PM +0000, Summers, Stuart wrote: > > > On Tue, 2019-05-14 at 17:53 +0100, Chris Wilson wrote: > > > > Quoting Stuart Summers (2019-05-14 17:46:52) > > > > > To allow easier debug of platforms which do not fully support > > > > > power-saving render C-state 6, add back the module parameter > > > > > to allow RC6 flows to be disabled. Instead of directly > > > > > affecting > > > > > the RC6 states via a bitmask as done previously, use this > > > > > module > > > > > parameter to clear the has_rc6 field for these platforms. > > > > > > > > If you know which platforms don't support rc6, don't enable > > > > rc6. > > > > > > I'd really prefer to have this parameter in place for debug > > > purposes. > > > It seems more useful to allow quick testing by reloading i915 > > > than by > > > requiring a rebuild. > > > > > > Of course, once debug is complete and the platform is known to > > > either > > > not support the feature or has some cripling bug around this, I > > > agree, > > > rc6 shouldn't be enabled on that platform and i915 should be > > > updated. > > > > Exactly. We need the flexibility for debug that. > > unfortunately using debugfs doesn't look a solution. > > > > One possibility that just came to my mind now is, what if we make > > this only for platforms that are still protected by > > is_alpha_support=1 > > (soon becoming require_force_probe=1) > > > > But this is just one side of the coin... when product is out there > > and we want the user to debug the issue to see if it is a RC6 bug > > we have no way to verify that. :/ > > > > Please let's add this back one way or another. > > To throw a compromise option out there - add the modparam for debug > builds only (CONFIG_DRM_I915_DEBUG)? No issues here, and makes sense. If we have concensus, I'd be happy to add this and repost. -Stuart > > Regards, > > Tvrtko
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