Re: [PATCH 6/6] drm/i915/icl: Support co-existence between per-context SSEU and OA

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

Hi,

One final unreviewed patch on this series. Hopefully uncontroversial 
enough for a quick review?

Thanks,

Tvrtko

On 17/09/2018 12:30, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> 
> When OA is active we want to lock the powergating configuration, but on
> Icelake, users like the media stack will have issues if we lock to the
> full device configuration.
> 
> Instead lock to a subset of (sub)slices which are currently a known
> working configuration for all users.
> 
> v2:
>   * Fix commit message spelling.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> ---
>   drivers/gpu/drm/i915/intel_lrc.c | 25 ++++++++++++++++++++-----
>   1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index b5603e977a3f..cded1f1d9ec2 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -2521,13 +2521,28 @@ u32 gen8_make_rpcs(struct drm_i915_private *i915, struct intel_sseu *req_sseu)
>   
>   	/*
>   	 * If i915/perf is active, we want a stable powergating configuration
> -	 * on the system. The most natural configuration to take in that case
> -	 * is the default (i.e maximum the hardware can do).
> +	 * on the system.
> +	 *
> +	 * We could choose full enablement, but on ICL we know there are use
> +	 * cases which disable slices for functional, apart for performance
> +	 * reasons. So in this case we select a known stable subset.
>   	 */
> -	if (unlikely(i915->perf.oa.exclusive_stream))
> -		ctx_sseu = intel_device_default_sseu(i915);
> -	else
> +	if (!i915->perf.oa.exclusive_stream) {
>   		ctx_sseu = *req_sseu;
> +	} else {
> +		ctx_sseu = intel_device_default_sseu(i915);
> +
> +		if (IS_GEN11(i915)) {
> +			/*
> +			 * We only need subslice count so it doesn't matter
> +			 * which ones we select - just turn of low bits in the
> +			 * amount of half of all available subslices per slice.
> +			 */
> +			ctx_sseu.subslice_mask =
> +				~(~0 << (hweight8(ctx_sseu.subslice_mask) / 2));
> +			ctx_sseu.slice_mask = 0x1;
> +		}
> +	}
>   
>   	slices = hweight8(ctx_sseu.slice_mask);
>   	subslices = hweight8(ctx_sseu.subslice_mask);
> 
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