Re: [PATCH 08/26] drm/i915/guc: Add multi-lrc context registration

[John Harrison <john.c.harrison@intel.com>]

On 10/4/2021 15:06, Matthew Brost wrote:
> Add multi-lrc context registration H2G. In addition a workqueue and
> process descriptor are setup during multi-lrc context registration as
> these data structures are needed for multi-lrc submission.
>
> v2:
>   (John Harrison)
>    - Move GuC specific fields into sub-struct
>    - Clean up WQ defines
>    - Add comment explaining math to derive WQ / PD address
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/i915/gt/intel_context_types.h |  12 ++
>   drivers/gpu/drm/i915/gt/intel_lrc.c           |   5 +
>   .../gpu/drm/i915/gt/uc/abi/guc_actions_abi.h  |   1 +
>   drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   |   2 -
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 114 +++++++++++++++++-
>   5 files changed, 131 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 76dfca57cb45..48decb5ee954 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -239,6 +239,18 @@ struct intel_context {
>   		struct intel_context *parent;
>   		/** @number_children: number of children if parent */
>   		u8 number_children;
> +		/** @guc: GuC specific members for parallel submission */
> +		struct {
> +			/** @wqi_head: head pointer in work queue */
> +			u16 wqi_head;
> +			/** @wqi_tail: tail pointer in work queue */
> +			u16 wqi_tail;
> +			/**
> +			 * @parent_page: page in context state (ce->state) used
> +			 * by parent for work queue, process descriptor
> +			 */
> +			u8 parent_page;
> +		} guc;
>   	} parallel;
>   
>   #ifdef CONFIG_DRM_I915_SELFTEST
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 3ef9eaf8c50e..57339d5c1fc8 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -942,6 +942,11 @@ __lrc_alloc_state(struct intel_context *ce, struct intel_engine_cs *engine)
>   		context_size += PAGE_SIZE;
>   	}
>   
> +	if (intel_context_is_parent(ce) && intel_engine_uses_guc(engine)) {
> +		ce->parallel.guc.parent_page = context_size / PAGE_SIZE;
> +		context_size += PAGE_SIZE;
> +	}
> +
>   	obj = i915_gem_object_create_lmem(engine->i915, context_size,
>   					  I915_BO_ALLOC_PM_VOLATILE);
>   	if (IS_ERR(obj))
> diff --git a/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h b/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> index 8ff582222aff..ba10bd374cee 100644
> --- a/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> +++ b/drivers/gpu/drm/i915/gt/uc/abi/guc_actions_abi.h
> @@ -142,6 +142,7 @@ enum intel_guc_action {
>   	INTEL_GUC_ACTION_REGISTER_COMMAND_TRANSPORT_BUFFER = 0x4505,
>   	INTEL_GUC_ACTION_DEREGISTER_COMMAND_TRANSPORT_BUFFER = 0x4506,
>   	INTEL_GUC_ACTION_DEREGISTER_CONTEXT_DONE = 0x4600,
> +	INTEL_GUC_ACTION_REGISTER_CONTEXT_MULTI_LRC = 0x4601,
>   	INTEL_GUC_ACTION_RESET_CLIENT = 0x5507,
>   	INTEL_GUC_ACTION_LIMIT
>   };
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> index fa4be13c8854..0eeb2a9feeed 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> @@ -52,8 +52,6 @@
>   
>   #define GUC_DOORBELL_INVALID		256
>   
> -#define GUC_WQ_SIZE			(PAGE_SIZE * 2)
> -
>   /* Work queue item header definitions */
>   #define WQ_STATUS_ACTIVE		1
>   #define WQ_STATUS_SUSPENDED		2
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 451d9ae861a6..ab6d7fc1b0b1 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -344,6 +344,45 @@ static inline struct i915_priolist *to_priolist(struct rb_node *rb)
>   	return rb_entry(rb, struct i915_priolist, node);
>   }
>   
> +/*
> + * When using multi-lrc submission an extra page in the context state is
> + * reserved for the process descriptor and work queue.
> + *
> + * The layout of this page is below:
> + * 0						guc_process_desc
> + * ...						unused
> + * PAGE_SIZE / 2				work queue start
> + * ...						work queue
> + * PAGE_SIZE - 1				work queue end
> + */
> +#define WQ_SIZE			(PAGE_SIZE / 2)
> +#define WQ_OFFSET		(PAGE_SIZE - WQ_SIZE)
I thought you were going with '#define PARENT_SCRATCH SIZE PAGE_SIZE' 
and then using that everywhere else? Unless there is a fundamental 
reason why the above must be exactly a page in size then I think the 
size should be defined once and re-used rather than assumed in multiple 
places (including in the description comment).

> +static u32 __get_process_desc_offset(struct intel_context *ce)
> +{
> +	GEM_BUG_ON(!ce->parallel.guc.parent_page);
> +
> +	return ce->parallel.guc.parent_page * PAGE_SIZE;
> +}
> +
> +static u32 __get_wq_offset(struct intel_context *ce)
> +{
> +	return __get_process_desc_offset(ce) + WQ_OFFSET;
> +}
> +
> +static struct guc_process_desc *
> +__get_process_desc(struct intel_context *ce)
> +{
> +	/*
> +	 * Need to subtract LRC_STATE_OFFSET here as the
> +	 * parallel.guc.parent_page is the offset into ce->state while
> +	 * ce->lrc_reg_reg is ce->state + LRC_STATE_OFFSET.
> +	 */
> +	return (struct guc_process_desc *)
> +		(ce->lrc_reg_state +
> +		 ((__get_process_desc_offset(ce) -
> +		   LRC_STATE_OFFSET) / sizeof(u32)));
> +}
> +
>   static struct guc_lrc_desc *__get_lrc_desc(struct intel_guc *guc, u32 index)
>   {
>   	struct guc_lrc_desc *base = guc->lrc_desc_pool_vaddr;
> @@ -1365,6 +1404,30 @@ static void unpin_guc_id(struct intel_guc *guc, struct intel_context *ce)
>   	spin_unlock_irqrestore(&guc->submission_state.lock, flags);
>   }
>   
> +static int __guc_action_register_multi_lrc(struct intel_guc *guc,
> +					   struct intel_context *ce,
> +					   u32 guc_id,
> +					   u32 offset,
> +					   bool loop)
> +{
> +	struct intel_context *child;
> +	u32 action[4 + MAX_ENGINE_INSTANCE];
> +	int len = 0;
> +
> +	GEM_BUG_ON(ce->parallel.number_children > MAX_ENGINE_INSTANCE);
> +
> +	action[len++] = INTEL_GUC_ACTION_REGISTER_CONTEXT_MULTI_LRC;
> +	action[len++] = guc_id;
> +	action[len++] = ce->parallel.number_children + 1;
> +	action[len++] = offset;
> +	for_each_child(ce, child) {
> +		offset += sizeof(struct guc_lrc_desc);
> +		action[len++] = offset;
> +	}
> +
> +	return guc_submission_send_busy_loop(guc, action, len, 0, loop);
> +}
> +
>   static int __guc_action_register_context(struct intel_guc *guc,
>   					 u32 guc_id,
>   					 u32 offset,
> @@ -1387,9 +1450,15 @@ static int register_context(struct intel_context *ce, bool loop)
>   		ce->guc_id.id * sizeof(struct guc_lrc_desc);
>   	int ret;
>   
> +	GEM_BUG_ON(intel_context_is_child(ce));
>   	trace_intel_context_register(ce);
>   
> -	ret = __guc_action_register_context(guc, ce->guc_id.id, offset, loop);
> +	if (intel_context_is_parent(ce))
> +		ret = __guc_action_register_multi_lrc(guc, ce, ce->guc_id.id,
> +						      offset, loop);
> +	else
> +		ret = __guc_action_register_context(guc, ce->guc_id.id, offset,
> +						    loop);
>   	if (likely(!ret)) {
>   		unsigned long flags;
>   
> @@ -1418,6 +1487,7 @@ static int deregister_context(struct intel_context *ce, u32 guc_id)
>   {
>   	struct intel_guc *guc = ce_to_guc(ce);
>   
> +	GEM_BUG_ON(intel_context_is_child(ce));
>   	trace_intel_context_deregister(ce);
>   
>   	return __guc_action_deregister_context(guc, guc_id);
> @@ -1445,6 +1515,7 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
>   	struct guc_lrc_desc *desc;
>   	bool context_registered;
>   	intel_wakeref_t wakeref;
> +	struct intel_context *child;
>   	int ret = 0;
>   
>   	GEM_BUG_ON(!engine->mask);
> @@ -1470,6 +1541,41 @@ static int guc_lrc_desc_pin(struct intel_context *ce, bool loop)
>   	desc->context_flags = CONTEXT_REGISTRATION_FLAG_KMD;
>   	guc_context_policy_init(engine, desc);
>   
> +	/*
> +	 * Context is a parent, we need to register a process descriptor
> +	 * describing a work queue and register all child contexts.
> +	 */
This was now meant to say 'If the context is a parent...'?

John.

> +	if (intel_context_is_parent(ce)) {
> +		struct guc_process_desc *pdesc;
> +
> +		ce->parallel.guc.wqi_tail = 0;
> +		ce->parallel.guc.wqi_head = 0;
> +
> +		desc->process_desc = i915_ggtt_offset(ce->state) +
> +			__get_process_desc_offset(ce);
> +		desc->wq_addr = i915_ggtt_offset(ce->state) +
> +			__get_wq_offset(ce);
> +		desc->wq_size = WQ_SIZE;
> +
> +		pdesc = __get_process_desc(ce);
> +		memset(pdesc, 0, sizeof(*(pdesc)));
> +		pdesc->stage_id = ce->guc_id.id;
> +		pdesc->wq_base_addr = desc->wq_addr;
> +		pdesc->wq_size_bytes = desc->wq_size;
> +		pdesc->wq_status = WQ_STATUS_ACTIVE;
> +
> +		for_each_child(ce, child) {
> +			desc = __get_lrc_desc(guc, child->guc_id.id);
> +
> +			desc->engine_class =
> +				engine_class_to_guc_class(engine->class);
> +			desc->hw_context_desc = child->lrc.lrca;
> +			desc->priority = ce->guc_state.prio;
> +			desc->context_flags = CONTEXT_REGISTRATION_FLAG_KMD;
> +			guc_context_policy_init(engine, desc);
> +		}
> +	}
> +
>   	/*
>   	 * The context_lookup xarray is used to determine if the hardware
>   	 * context is currently registered. There are two cases in which it
> @@ -2804,6 +2910,12 @@ g2h_context_lookup(struct intel_guc *guc, u32 desc_idx)
>   		return NULL;
>   	}
>   
> +	if (unlikely(intel_context_is_child(ce))) {
> +		drm_err(&guc_to_gt(guc)->i915->drm,
> +			"Context is child, desc_idx %u", desc_idx);
> +		return NULL;
> +	}
> +
>   	return ce;
>   }
>