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Commit 551aaecd authored by Dave Gordon's avatar Dave Gordon Committed by Tvrtko Ursulin
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drm/i915/guc: don't spinwait if the GuC's workqueue is full 



Rather than wait to see whether more space becomes available in the GuC
submission workqueue, we can just return -EAGAIN and let the caller try
again in a little while. This gets rid of an uninterruptable sleep in
the polling code :)

We'll also add a counter to the GuC client statistics, to see how often
we find the WQ full.

v2:
    Flag the likely() code path (Tvtrko Ursulin).

v4:
    Add/update comments about failure counters (Tvtrko Ursulin).

Signed-off-by: default avatarDave Gordon <david.s.gordon@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
parent 7c2c270d

drivers/gpu/drm/i915/i915_debugfs.c

+1 −0
Original line number Diff line number Diff line
@@ -2515,6 +2515,7 @@ static void i915_guc_client_info(struct seq_file *m, 
	seq_printf(m, "\tWQ size %d, offset: 0x%x, tail %d\n",

		client->wq_size, client->wq_offset, client->wq_tail);



	seq_printf(m, "\tWork queue full: %u\n", client->no_wq_space);

	seq_printf(m, "\tFailed to queue: %u\n", client->q_fail);

	seq_printf(m, "\tFailed doorbell: %u\n", client->b_fail);

	seq_printf(m, "\tLast submission result: %d\n", client->retcode);

drivers/gpu/drm/i915/i915_guc_submission.c

+7 −11
Original line number Diff line number Diff line
@@ -468,26 +468,22 @@ static void guc_fini_ctx_desc(struct intel_guc *guc, 
 */

int i915_guc_wq_check_space(struct drm_i915_gem_request *request)

{

	const size_t size = sizeof(struct guc_wq_item);

	const size_t wqi_size = sizeof(struct guc_wq_item);

	struct i915_guc_client *gc = request->i915->guc.execbuf_client;

	struct guc_process_desc *desc;

	int ret = -ETIMEDOUT, timeout_counter = 200;

	u32 freespace;



	GEM_BUG_ON(gc == NULL);



	desc = gc->client_base + gc->proc_desc_offset;



	while (timeout_counter-- > 0) {

		if (CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size) >= size) {

			ret = 0;

			break;

		}

	freespace = CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size);

	if (likely(freespace >= wqi_size))

		return 0;



		if (timeout_counter)

			usleep_range(1000, 2000);

	};

	gc->no_wq_space += 1;



	return ret;

	return -EAGAIN;

}



static int guc_add_workqueue_item(struct i915_guc_client *gc,

drivers/gpu/drm/i915/intel_guc.h

+16 −6
Original line number Diff line number Diff line
@@ -48,9 +48,18 @@ struct drm_i915_gem_request; 
 * queue (a circular array of work items), again described in the process

 * descriptor. Work queue pages are mapped momentarily as required.

 *

 * Finally, we also keep a few statistics here, including the number of

 * submissions to each engine, and a record of the last submission failure

 * (if any).

 * We also keep a few statistics on failures. Ideally, these should all

 * be zero!

 *   no_wq_space: times that the submission pre-check found no space was

 *                available in the work queue (note, the queue is shared,

 *                not per-engine). It is OK for this to be nonzero, but

 *                it should not be huge!

 *   q_fail: failed to enqueue a work item. This should never happen,

 *           because we check for space beforehand.

 *   b_fail: failed to ring the doorbell. This should never happen, unless

 *           somehow the hardware misbehaves, or maybe if the GuC firmware

 *           crashes? We probably need to reset the GPU to recover.

 *   retcode: errno from last guc_submit()

 */

struct i915_guc_client {

	struct drm_i915_gem_object *client_obj;
@@ -71,12 +80,13 @@ struct i915_guc_client { 
	uint32_t wq_tail;

	uint32_t unused;		/* Was 'wq_head'		*/



	/* GuC submission statistics & status */

	uint64_t submissions[GUC_MAX_ENGINES_NUM];

	uint32_t no_wq_space;

	uint32_t q_fail;

	uint32_t b_fail;

	int retcode;

	int spare;			/* pad to 32 DWords		*/



	/* Per-engine counts of GuC submissions */

	uint64_t submissions[GUC_MAX_ENGINES_NUM];

};



enum intel_guc_fw_status {