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

[Summers, Stuart]

On Thu, 2019-10-24 at 09:29 -0700, 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.
> 
> 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)

Hey Don,

I might be missing something here, but glancing over the code for
submission_supported, it looks like this relies on the availability of
the firmware for the intended platform. Looking at the GuC table for
KBL, I do see this present (using KBL per your commit above). So
wouldn't this return true here if enable_guc is set to 1 or 3?

Thanks,
Stuart

> +		return intel_guc_send(guc, action, ARRAY_SIZE(action));
> +
> +	return 0;
>  }
>  
>  /**
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