Re: [PATCH v2 2/2] drm/i915/gt: Enable only one CCS for compute workload

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

On 20/02/2024 14:35, Andi Shyti wrote:
> Enable only one CCS engine by default with all the compute sices

slices

> allocated to it.
> 
> While generating the list of UABI engines to be exposed to the
> user, exclude any additional CCS engines beyond the first
> instance.
> 
> This change can be tested with igt i915_query.
> 
> Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: <stable@vger.kernel.org> # v6.2+
> ---
>   drivers/gpu/drm/i915/gt/intel_engine_user.c |  9 +++++++++
>   drivers/gpu/drm/i915/gt/intel_gt.c          | 11 +++++++++++
>   drivers/gpu/drm/i915/gt/intel_gt_regs.h     |  2 ++
>   drivers/gpu/drm/i915/i915_query.c           |  1 +
>   4 files changed, 23 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> index 833987015b8b..7041acc77810 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_user.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c
> @@ -243,6 +243,15 @@ void intel_engines_driver_register(struct drm_i915_private *i915)
>   		if (engine->uabi_class == I915_NO_UABI_CLASS)
>   			continue;
>   
> +		/*
> +		 * Do not list and do not count CCS engines other than the first
> +		 */
> +		if (engine->uabi_class == I915_ENGINE_CLASS_COMPUTE &&
> +		    engine->uabi_instance > 0) {
> +			i915->engine_uabi_class_count[engine->uabi_class]--;
> +			continue;
> +		}

It's a bit ugly to decrement after increment, instead of somehow 
restructuring the loop to satisfy both cases more elegantly. And I 
wonder if internally (in dmesg when engine name is logged) we don't end 
up with ccs0 ccs0 ccs0 ccs0.. for all instances.

> +
>   		rb_link_node(&engine->uabi_node, prev, p);
>   		rb_insert_color(&engine->uabi_node, &i915->uabi_engines);
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index a425db5ed3a2..e19df4ef47f6 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -168,6 +168,14 @@ static void init_unused_rings(struct intel_gt *gt)
>   	}
>   }
>   
> +static void intel_gt_apply_ccs_mode(struct intel_gt *gt)
> +{
> +	if (!IS_DG2(gt->i915))
> +		return;
> +
> +	intel_uncore_write(gt->uncore, XEHP_CCS_MODE, 0);
> +}
> +
>   int intel_gt_init_hw(struct intel_gt *gt)
>   {
>   	struct drm_i915_private *i915 = gt->i915;
> @@ -195,6 +203,9 @@ int intel_gt_init_hw(struct intel_gt *gt)
>   
>   	intel_gt_init_swizzling(gt);
>   
> +	/* Configure CCS mode */
> +	intel_gt_apply_ccs_mode(gt);
> +
>   	/*
>   	 * At least 830 can leave some of the unused rings
>   	 * "active" (ie. head != tail) after resume which
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> index cf709f6c05ae..c148113770ea 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> @@ -1605,6 +1605,8 @@
>   #define   GEN12_VOLTAGE_MASK			REG_GENMASK(10, 0)
>   #define   GEN12_CAGF_MASK			REG_GENMASK(19, 11)
>   
> +#define XEHP_CCS_MODE                          _MMIO(0x14804)
> +
>   #define GEN11_GT_INTR_DW(x)			_MMIO(0x190018 + ((x) * 4))
>   #define   GEN11_CSME				(31)
>   #define   GEN12_HECI_2				(30)
> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> index 3baa2f54a86e..d5a5143971f5 100644
> --- a/drivers/gpu/drm/i915/i915_query.c
> +++ b/drivers/gpu/drm/i915/i915_query.c
> @@ -124,6 +124,7 @@ static int query_geometry_subslices(struct drm_i915_private *i915,
>   	return fill_topology_info(sseu, query_item, sseu->geometry_subslice_mask);
>   }
>   
> +

Zap please.

>   static int
>   query_engine_info(struct drm_i915_private *i915,
>   		  struct drm_i915_query_item *query_item)

Regards,

Tvrtko