[Intel-gfx] [PATCH] drm/i915/uc: don't enable communication twice on resume

[Chris Wilson]

Quoting Daniele Ceraolo Spurio (2019-07-30 17:05:19)
> 
> 
> On 7/30/19 1:14 AM, Chris Wilson wrote:
> > Quoting Daniele Ceraolo Spurio (2019-07-29 23:28:00)
> >> When coming out of S3/S4 we sanitize and re-init the HW, which includes
> >> enabling communication during uc_init_hw. We therefore don't want to do
> >> that again in uc_resume and can just tell GuC to reload its state.
> >>
> >> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> >> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> >> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> >> ---
> >>   drivers/gpu/drm/i915/gt/uc/intel_uc.c | 16 +++++++++++++++-
> >>   1 file changed, 15 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_uc.c b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> >> index fafa9be1e12a..34706a753793 100644
> >> --- a/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> >> +++ b/drivers/gpu/drm/i915/gt/uc/intel_uc.c
> >> @@ -233,11 +233,18 @@ static void guc_disable_interrupts(struct intel_guc *guc)
> >>          guc->interrupts.disable(guc);
> >>   }
> >>   
> >> +static bool guc_communication_enabled(struct intel_guc *guc)
> >> +{
> >> +       return guc->send != intel_guc_send_nop;
> >> +}
> >> +
> >>   static int guc_enable_communication(struct intel_guc *guc)
> >>   {
> >>          struct drm_i915_private *i915 = guc_to_gt(guc)->i915;
> >>          int ret;
> >>   
> >> +       GEM_BUG_ON(guc_communication_enabled(guc));
> >> +
> >>          ret = intel_guc_ct_enable(&guc->ct);
> >>          if (ret)
> >>                  return ret;
> >> @@ -558,7 +565,14 @@ int intel_uc_resume(struct intel_uc *uc)
> >>          if (!intel_guc_is_running(guc))
> >>                  return 0;
> >>   
> >> -       guc_enable_communication(guc);
> >> +       /*
> >> +        * When coming out of S3/S4 we sanitize and re-init the HW, so
> >> +        * communication is already re-enabled at this point and we just need
> >> +        * to tell GuC to reload its internal state. During runtime resume we
> >> +        * instead want to re-init everything.
> >> +        */
> >> +       if (!guc_communication_enabled(guc))
> >> +               guc_enable_communication(guc);
> > 
> > We distinguish runtime_suspend from suspend, but not runtime_resume from
> > resume. Is that distinction worthwhile, could we use it be more strict
> > over the expected state?
> 
> The actual actions we want to perform in both cases are the same, apart 
> from the communication side. What about:
> 
> static int __uc_resume(struct intel_uc *uc, bool enable_comm)
> {
>         if (!intel_guc_is_running())
>                 return 0;
> 
>         GEM_BUG_ON(enable comm == guc_communication_enabled());
> 
>         if (enable_comm)
>                 guc_enable_communication();
> 
>         err = intel_guc_resume();
> }
> 
> intel_uc_runtime_resume()
> {
>         __uc_resume(uc, true);
> }
> 
> intel_uc_resume()
> {
>         __uc_resume(uc, false);
> }

That works for me. Having uc->suspend unnerved me worrying about what
happens if gets out of sync. I like having the link from drm_resume ->
uc_resume and drm_runtime_resume -> uc_runtime_resume.
-Chris