[Intel-gfx] [PATCH] drm/i915/guc: Skip suspend/resume GuC action on platforms w/o GuC submission

[Hiatt, Don]

> From: Wajdeczko, Michal <Michal.Wajdeczko at intel.com>
> Sent: Tuesday, October 29, 2019 5:33 AM
> To: intel-gfx at lists.freedesktop.org; Hiatt, Don <don.hiatt at intel.com>
> Subject: Re: [Intel-gfx] [PATCH] drm/i915/guc: Skip suspend/resume GuC action
> on platforms w/o GuC submission
> 
> On Mon, 28 Oct 2019 22:25:27 +0100, <don.hiatt at intel.com> wrote:
> 
> > From: Don Hiatt <don.hiatt at intel.com>
> >
> > On some platforms (e.g. KBL) that do not support GuC submission, but
> > the user enabled the GuC communication (e.g for HuC authentication)
> > calling the GuC EXIT_S_STATE action results in lose of ability to
> > enter RC6. We can remove the GuC suspend/remove entirely as we do
> > not need to save the GuC submission status.
> >
> > v2: Do not suspend/resume the GuC on platforms that do not support
> >     Guc Submission.
> >
> > Signed-off-by: Don Hiatt <don.hiatt at intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/uc/intel_uc.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > index 3fdbc935d155..04031564f0b1 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> > @@ -572,10 +572,19 @@ void intel_uc_runtime_suspend(struct intel_uc *uc)
> >  	if (!intel_guc_is_running(guc))
> >  		return;
> > +	/*
> > +	 * If GuC communciation is enabled but submission is not supported,
> 
> typo
> 
> > +	 * we do not need to suspend the GuC but we do need to disable the
> > +	 * GuC communication on suspend.
> > +	 */
> > +	if (!guc->submission_supported)
> 
> Using submission_supported flag directly can be tricky, as today it
> is always set to false, but in the future it may indicate either that
> submission is supported by the driver/fw and/or enabled by modparam.
> 
> There is no guarantee that it will reflect actual runtime status,
> as even supported/unblocked guc submission may fallback to execlists.
> 
> We may need something like intel_guc_submission_is_active() that will
> reflect actual mode of submission currently used by the driver.

Hi Michal,

I looked at your patch wrt checking the set_default_submission vfunc but
as that is for the engine, and here I only have access to the intel_guc struct.
I'm not sure just where I can know what the default submission is and then
flag it somewhere that I can then check here in the suspend/resume. I'll keep
looking (sorry, I'm very new to this code). 😊

Thanks,

don






> 
> > +		goto guc_disable_comm;
> 
> and maybe we can move above logic to intel_guc_suspend()
> to do not introduce extra goto's ?
> 
> > +
> >  	err = intel_guc_suspend(guc);
> >  	if (err)
> >  		DRM_DEBUG_DRIVER("Failed to suspend GuC, err=%d", err);
> > +guc_disable_comm:
> >  	guc_disable_communication(guc);
> >  }
> > @@ -605,6 +614,14 @@ static int __uc_resume(struct intel_uc *uc, bool
> > enable_communication)
> >  	if (enable_communication)
> >  		guc_enable_communication(guc);
> > +	/*
> > +	 * If GuC communciation is enabled but submission is not supported,
> 
> typo
> 
> > +	 * we do not need to resume the GuC but we do need to enable the
> > +	 * GuC communication on resume (above).
> > +	 */
> > +	if (!guc->submission_supported)
> > +		return 0;
> 
> see suspend case comment
> 
> > +
> >  	err = intel_guc_resume(guc);
> >  	if (err) {
> >  		DRM_DEBUG_DRIVER("Failed to resume GuC, err=%d", err);
> 
> Thanks,
> Michal