On Mon, May 23, 2016 at 05:09:43PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > On SNB (at least) it's dangeruopus to hang the GPU with an infinite > batch buffer loop while RPS is disabled. The only thing that keeps > the system going in such circumstances are the internal RPS timers, > so we should never feed the GPU with RPS disabled unless we want to > risk a total system hang. > > Previously we didn't fully disable RPS, but that changes in > commit 2030d684f7b3 ("drm/i915/bxt: Explicitly clear the Turbo control register") > so we probably didn't see the problem so often previously. But > even before that we were at the mercy of the BIOS for the initial > RPS state, so if the BIOS didn't enable RPS a GPU hang immediately > upon boot could have been fatal. > > To avoid the problems let's just make the RPS enable immediate. > This renders the delayed_resume_work useless actually. We could perhaps > just move the ring freq table initialization to the work and do the > other stull synchronously? > > Fixes: 2030d684f7b3 ("drm/i915/bxt: Explicitly clear the Turbo control register") > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > --- > This is more and RFC at this point. Perhaps we might want to keep the delayed > work but just for the ring freq table update (which is the main reson this whole > thing exists in the first place). Another factor is that wait_for() is not > exactly optiomal currently, so it makes the operation slower than it needs to > be. Would need some hard numbers to see if it's worth keeping the delayed work > or not I suppose. Loading the ring freq tables takes forever, so definitely want to keep that. I'd just split rps setup in two parts and push the schedule_work down a bit. Long term we can go overboard with async (and maybey only stall for all the GT setup in the very first batchbuffer). -Daniel > > drivers/gpu/drm/i915/intel_pm.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c > index 817c84c22782..e65c5c2b9b4e 100644 > --- a/drivers/gpu/drm/i915/intel_pm.c > +++ b/drivers/gpu/drm/i915/intel_pm.c > @@ -6505,6 +6505,7 @@ void intel_enable_gt_powersave(struct drm_i915_private *dev_priv) > if (schedule_delayed_work(&dev_priv->rps.delayed_resume_work, > round_jiffies_up_relative(HZ))) > intel_runtime_pm_get_noresume(dev_priv); > + flush_delayed_work(&dev_priv->rps.delayed_resume_work); > } > } > > -- > 2.7.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx