[Intel-gfx] [PATCH] drm/i915/gen9bc: Handle TGP PCH during suspend/resume

[Imre Deak]

On Wed, Feb 10, 2021 at 06:33:20AM +0200, Gupta, Anshuman wrote:
> > On Tue, 2021-02-02 at 18:14 +0200, Imre Deak wrote:
> > >
> > > BSpec says about this WA for both ICL and TGL:
> > > """
> > > Display driver should set and clear register offset 0xC2000 bit #7 as
> > > last step in programming south display registers in preparation for
> > > entering S0ix state, or set 0xC2000 bit #7 on S0ix entry and clear it
> > > on S0ix exit.
> > >
> > > """
> > >
> > > This means to me the WA is only relevant for S0ix and we can implement
> > > it by setting/clearing 0xC2000 bit #7 right before entering/right
> > > after exiting S0ix. This is done atm on PCH_ICP..PCH_MCC in
> > > intel_display_power_suspend_late()/intel_display_power_resume_early(),
> > > so I'd move the WA for all platforms there.
> > >
> > > I assume the current code in irq_reset() was the first alternative to
> > > implement the WA, but it wasn't enough. Not sure why, maybe there is a
> > > south display register access after irq_reset() during suspend. Adding
> > > Anshuman for an idea on that.
> > >
> > 
> > Poking Anshuman here, is there any update on this? I'm looking to push these
> > patches forward as some of Red Hat's hardware partners are very eager for this
> > to get upstream asap as we're running out of time from our end. If you can
> > answer this, I can handle respinning this patch as needed.
>
> My sincere apology, I had missed this thread.  We have decided to keep
> the alternative WA i.e  setting/clearing 0xC2000 bit #7 before
> entering after exiting s0ix to fix the deeper s0ix power consumption
> issues on ICL_PCH families platforms. This alternative WA  was added
> to B.Spec on our request.  But on TGL_PCH first alternative WA logic
> i.e  in irq_reset() was working to attain deeper s0ix residencies so
> we haven't changed that.

Ok, thanks for the explanation. For now I'd just ask to add a TODO: in
this patch to check if the WA can be applied in the s0ix suspend/resume
handlers as on earlier platforms and whether the WA is also needed for
runtime s/r.

--Imre