[Intel-gfx] [PATCH] drm/i914/guc: Fix resume on platforms w/o GuC submission but enabled

[Hiatt, Don]

> From: Ceraolo Spurio, Daniele <daniele.ceraolospurio at intel.com>
> Sent: Monday, October 28, 2019 9:44 AM
> To: Hiatt, Don <don.hiatt at intel.com>; intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i914/guc: Fix resume on platforms w/o GuC
> submission but enabled
> 
> 
> 
> On 10/24/19 9:29 AM, don.hiatt at intel.com wrote:
> > From: Don Hiatt <don.hiatt at intel.com>
> >
> > Check to see if GuC submission is enabled before requesting the
> > EXIT_S_STATE action.
> >
> 
> You're only skipping the resume, but does it make any sense to do the
> suspend action if we're not going to call the resume one? Does guc do
> anything in the suspend action that we still require? I thought it only
> saved the submission status, which we don't care about if guc submission
> is disabled.
> 
> Daniele
> 

Hi Daniele,

I tried skipping the suspend all together but then the HuC gets timeouts
waiting for the GuC to acknowledge the authentication request which leads to a
wedged GPU. ☹ 

BTW, I made a typo in the patch, should be 'drm/i915' not '914', I'll fix that
up.

Thanks,

don


> > 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. Guard against this by only requesting the GuC action on
> > platforms that support GuC submission.
> >
> > I've verfied that intel_guc_resume() only gets called when driver
> > is loaded with: guc_enable={1,2,3}, all other cases (no args,
> > guc_enable={0,-1} the intel_guc_resume() is not called.
> >
> > Signed-off-by: Don Hiatt <don.hiatt at intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/uc/intel_guc.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> > index 37f7bcbf7dac..33318ed135c0 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> > @@ -565,7 +565,10 @@ int intel_guc_resume(struct intel_guc *guc)
> >   		GUC_POWER_D0,
> >   	};
> >
> > -	return intel_guc_send(guc, action, ARRAY_SIZE(action));
> > +	if (guc->submission_supported)
> > +		return intel_guc_send(guc, action, ARRAY_SIZE(action));
> > +
> > +	return 0;
> >   }
> >
> >   /**
> >