[Intel-gfx] [PATCH 2/3] drm/i915/guc: drop cached copy of 'wq_head'

[Tvrtko Ursulin]

On 19/04/16 16:08, Dave Gordon wrote:
> From: Alex Dai <yu.dai at intel.com>
>
> Now that we keep the GuC client process descriptor permanently mapped,
> we don't really need to keep a local copy of the GuC's work-queue-head.
> So we can simplify the code a little by not doing this.
>
> Signed-off-by: Alex Dai <yu.dai at intel.com>
> Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_guc_submission.c | 16 ++++------------
>   drivers/gpu/drm/i915/intel_guc.h           |  2 +-
>   2 files changed, 5 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index d251699..4718b7a 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -238,9 +238,6 @@ static int guc_ring_doorbell(struct i915_guc_client *gc)
>   			db_exc.cookie = 1;
>   	}
>
> -	/* Finally, update the cached copy of the GuC's WQ head */
> -	gc->wq_head = desc->head;
> -
>   	return ret;
>   }
>
> @@ -465,17 +462,10 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
>   	if (!gc)
>   		return 0;
>
> -	/* Quickly return if wq space is available since last time we cache the
> -	 * head position. */
> -	if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size)
> -		return 0;
> -
>   	desc = gc->client_base + gc->proc_desc_offset;
>
>   	while (timeout_counter-- > 0) {
> -		gc->wq_head = desc->head;
> -
> -		if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size) {
> +		if (CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size) >= size) {
>   			ret = 0;
>   			break;
>   		}
> @@ -490,11 +480,13 @@ int i915_guc_wq_check_space(struct i915_guc_client *gc)
>   static int guc_add_workqueue_item(struct i915_guc_client *gc,
>   				  struct drm_i915_gem_request *rq)
>   {
> +	struct guc_process_desc *desc;
>   	struct guc_wq_item *wqi;
>   	void *base;
>   	u32 tail, wq_len, wq_off, space;
>
> -	space = CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size);
> +	desc = gc->client_base + gc->proc_desc_offset;
> +	space = CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size);
>   	if (WARN_ON(space < sizeof(struct guc_wq_item)))
>   		return -ENOSPC; /* shouldn't happen */
>
> diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
> index 06050c241a..19ca593 100644
> --- a/drivers/gpu/drm/i915/intel_guc.h
> +++ b/drivers/gpu/drm/i915/intel_guc.h
> @@ -46,7 +46,7 @@ struct i915_guc_client {
>   	uint32_t wq_offset;
>   	uint32_t wq_size;
>   	uint32_t wq_tail;
> -	uint32_t wq_head;
> +	uint32_t unused;		/* Was 'wq_head'		*/
>
>   	/* GuC submission statistics & status */
>   	uint64_t submissions[GUC_MAX_ENGINES_NUM];
>

Looks OK to me, only with a disclaimer that I am not a GuC expert:

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Regards,

Tvrtko