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

[Daniele Ceraolo Spurio]

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?
> -Chris
> 

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);
}

Daniele