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

[Gupta, Anshuman]

> -----Original Message-----
> From: Lyude Paul <lyude at redhat.com>
> Sent: Wednesday, February 10, 2021 1:34 AM
> To: Deak, Imre <imre.deak at intel.com>; Surendrakumar Upadhyay, TejaskumarX
> <tejaskumarx.surendrakumar.upadhyay at intel.com>; Gupta, Anshuman
> <anshuman.gupta at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; Pandey, Hariom
> <hariom.pandey at intel.com>
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/gen9bc: Handle TGP PCH during
> suspend/resume
> 
> ..snip.. (comments down below)
> 
> 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.

Thanks,
Anshuman Gupta
> 
> > --Imre
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
> 
> --
> Sincerely,
>    Lyude Paul (she/her)
>    Software Engineer at Red Hat
> 
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