Re: [PATCH v2 06/14] drm/i915/guc: Add a second client, to be used for preemption

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On Thu, 19 Oct 2017 20:36:11 +0200, Michał Winiarski <michal.winiarski@xxxxxxxxx> wrote:

From: Dave Gordon <david.s.gordon@xxxxxxxxx>

This second client is created with priority KMD_HIGH, and marked
as preemptive. This will allow us to request preemption using GuC actions.

v2: Extract clients creation into a helper, debugfs fixups. (Michał)
Recreate doorbell on init. (Daniele)
Move clients into an array.

Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
Signed-off-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>
Cc: Jeff McGee <jeff.mcgee@xxxxxxxxx>
Cc: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
Cc: Oscar Mateo <oscar.mateo@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_debugfs.c        |  11 +--
drivers/gpu/drm/i915/i915_guc_submission.c | 107 ++++++++++++++++++++---------
 drivers/gpu/drm/i915/intel_guc.h           |   9 ++-
 drivers/gpu/drm/i915/intel_uncore.c        |   2 +-
 4 files changed, 91 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index c65e381b85f3..daf7a16a4ee2 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2459,7 +2459,7 @@ static bool check_guc_submission(struct seq_file *m)
 	struct drm_i915_private *dev_priv = node_to_i915(m->private);
 	const struct intel_guc *guc = &dev_priv->guc;
-	if (!guc->execbuf_client) {
+	if (!guc->client[SUBMIT]) {
 		seq_printf(m, "GuC submission %s\n",
 			   HAS_GUC_SCHED(dev_priv) ?
 			   "disabled" :
@@ -2474,6 +2474,7 @@ static int i915_guc_info(struct seq_file *m, void *data)
 {
 	struct drm_i915_private *dev_priv = node_to_i915(m->private);
 	const struct intel_guc *guc = &dev_priv->guc;
+	u32 i;
	if (!check_guc_submission(m))
 		return 0;
@@ -2482,8 +2483,10 @@ static int i915_guc_info(struct seq_file *m, void *data)
 	seq_printf(m, "\t%*pb\n", GUC_NUM_DOORBELLS, guc->doorbell_bitmap);
 	seq_printf(m, "Doorbell next cacheline: 0x%x\n\n", guc->db_cacheline);
-	seq_printf(m, "\nGuC execbuf client @ %p:\n", guc->execbuf_client);
-	i915_guc_client_info(m, dev_priv, guc->execbuf_client);
+	for (i = 0; i < I915_GUC_NUM_CLIENTS; i++) {
+		seq_printf(m, "\nGuC client @ %p:\n", guc->client[i]);
+		i915_guc_client_info(m, dev_priv, guc->client[i]);
+	}
	i915_guc_log_info(m, dev_priv);
@@ -2497,7 +2500,7 @@ static int i915_guc_stage_pool(struct seq_file *m, void *data)
 	struct drm_i915_private *dev_priv = node_to_i915(m->private);
 	const struct intel_guc *guc = &dev_priv->guc;
 	struct guc_stage_desc *desc = guc->stage_desc_pool_vaddr;
-	struct i915_guc_client *client = guc->execbuf_client;
+	struct i915_guc_client *client = guc->client[SUBMIT];
 	unsigned int tmp;
 	int index;
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 0bd1fcffa78d..d8b8125aa4cc 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -33,10 +33,11 @@
  *
  * GuC client:
* A i915_guc_client refers to a submission path through GuC. Currently, there - * is only one of these (the execbuf_client) and this one is charged with all - * submissions to the GuC. This struct is the owner of a doorbell, a process - * descriptor and a workqueue (all of them inside a single gem object that
- * contains all required pages for these elements).
+ * are two clients. One of them (SUBMIT) is charged with all submissions to the + * GuC, the other one (PREEMPT) is responsible for preempting the SUBMIT one. + * This struct is the owner of a doorbell, a process descriptor and a workqueue + * (all of them inside a single gem object that contains all required pages for
+ * these elements).

Hmm, it's little unfortunate that SUBMIT and PREEMPT enums are defined
in intel_guc.h while mostly used in guc_submission.c

  *
  * GuC stage descriptor:
* During initialization, the driver allocates a static pool of 1024 such @@ -363,6 +364,8 @@ static void guc_stage_desc_init(struct intel_guc *guc,
 	memset(desc, 0, sizeof(*desc));
desc->attribute = GUC_STAGE_DESC_ATTR_ACTIVE | GUC_STAGE_DESC_ATTR_KERNEL;
+	if (client->priority <= GUC_CLIENT_PRIORITY_HIGH)
+		desc->attribute |= GUC_STAGE_DESC_ATTR_PREEMPT;
 	desc->stage_id = client->stage_id;
 	desc->priority = client->priority;
 	desc->db_id = client->doorbell_id;
@@ -553,7 +556,7 @@ static void i915_guc_submit(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
 	struct intel_guc *guc = &dev_priv->guc;
-	struct i915_guc_client *client = guc->execbuf_client;
+	struct i915_guc_client *client = guc->client[SUBMIT];

what about using helpers like:

static inline
struct i915_guc_client *guc_exec_client(struct intel_guc *guc)
{
	return guc->client[SUBMIT];
}

+	struct i915_guc_client *client = guc->client[SUBMIT];

 	struct intel_engine_execlists * const execlists = &engine->execlists;
 	struct execlist_port *port = execlists->port;
 	const unsigned int engine_id = engine->id;
@@ -750,10 +753,11 @@ static int __reset_doorbell(struct i915_guc_client* client, u16 db_id)
  */
 static int guc_init_doorbell_hw(struct intel_guc *guc)
 {
-	struct i915_guc_client *client = guc->execbuf_client;
+	struct i915_guc_client *client = guc->client[SUBMIT];
 	bool recreate_first_client = false;
 	u16 db_id;
 	int ret;
+	u32 i;
	/* For unused doorbells, make sure they are disabled */
 	for_each_clear_bit(db_id, guc->doorbell_bitmap, GUC_NUM_DOORBELLS) {
@@ -761,7 +765,7 @@ static int guc_init_doorbell_hw(struct intel_guc *guc)
 			continue;
		if (has_doorbell(client)) {
-			/* Borrow execbuf_client (we will recreate it later) */
+			/* Borrow submit client (we will recreate it later) */
 			destroy_doorbell(client);
 			recreate_first_client = true;
 		}
@@ -780,14 +784,14 @@ static int guc_init_doorbell_hw(struct intel_guc *guc)
 		__update_doorbell_desc(client, client->doorbell_id);
 	}
-	/* Now for every client (and not only execbuf_client) make sure their
+	/* Now for every client (not only submission client) make sure their
 	 * doorbells are known by the GuC */
-	//for (client = client_list; client != NULL; client = client->next)
+	for (i = 0; i < I915_GUC_NUM_CLIENTS; i++)
 	{
-		ret = __create_doorbell(client);
+		ret = __create_doorbell(guc->client[i]);
 		if (ret) {
 			DRM_ERROR("Couldn't recreate client %u doorbell: %d\n",
-				client->stage_id, ret);
+				  guc->client[i]->stage_id, ret);
 			return ret;
 		}
 	}
@@ -914,6 +918,47 @@ static void guc_client_free(struct i915_guc_client *client)
 	kfree(client);
 }
+static int guc_clients_create(struct intel_guc *guc)
+{
+	struct drm_i915_private *dev_priv = guc_to_i915(guc);
+	struct i915_guc_client *client;
+
+	client = guc_client_alloc(dev_priv,
+				  INTEL_INFO(dev_priv)->ring_mask,
+				  GUC_CLIENT_PRIORITY_KMD_NORMAL,
+				  dev_priv->kernel_context);
+	if (IS_ERR(client)) {
+		DRM_ERROR("Failed to create GuC client for submission!\n");
+		return PTR_ERR(client);
+	}
+	guc->client[SUBMIT] = client;
+
+	client = guc_client_alloc(dev_priv,
+				  INTEL_INFO(dev_priv)->ring_mask,
+				  GUC_CLIENT_PRIORITY_KMD_HIGH,
+				  dev_priv->preempt_context);
+	if (IS_ERR(client)) {
+		DRM_ERROR("Failed to create GuC client for preemption!\n");
+		guc_client_free(guc->client[SUBMIT]);
+		guc->client[SUBMIT] = NULL;
+		return PTR_ERR(client);
+	}
+	guc->client[PREEMPT] = client;
+
+	return 0;
+}
+
+static void guc_clients_destroy(struct intel_guc *guc)
+{
+	struct i915_guc_client *client;
+	u32 i;
+
+	for (i = 0; i < I915_GUC_NUM_CLIENTS; i++) {
+		client = fetch_and_zero(&guc->client[i]);
+		guc_client_free(client);
+	}
+}
+
 static void guc_policy_init(struct guc_policy *policy)
 {
 	policy->execution_quantum = POLICY_DEFAULT_EXECUTION_QUANTUM_US;
@@ -1143,7 +1188,6 @@ static void guc_interrupts_release(struct drm_i915_private *dev_priv)
 int i915_guc_submission_enable(struct drm_i915_private *dev_priv)
 {
 	struct intel_guc *guc = &dev_priv->guc;
-	struct i915_guc_client *client = guc->execbuf_client;
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 	int err;
@@ -1161,28 +1205,29 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv)
 		     sizeof(struct guc_wq_item) *
 		     I915_NUM_ENGINES > GUC_WQ_SIZE);
-	if (!client) {
-		client = guc_client_alloc(dev_priv,
-					  INTEL_INFO(dev_priv)->ring_mask,
-					  GUC_CLIENT_PRIORITY_KMD_NORMAL,
-					  dev_priv->kernel_context);
-		if (IS_ERR(client)) {
-			DRM_ERROR("Failed to create GuC client for execbuf!\n");
-			return PTR_ERR(client);
-		}
-
-		guc->execbuf_client = client;
+	/*
+	 * We're being called on both module initialization and on reset,
+	 * until this flow is changed, we're using regular client presence to
+	 * determine which case are we in, and whether we should allocate new
+	 * clients or just reset their workqueues.
+	 */
+	if (!guc->client[SUBMIT]) {
+		GEM_BUG_ON(guc->client[PREEMPT]);
+		err = guc_clients_create(guc);
+		if (err)
+			return err;
+	} else {
+		guc_reset_wq(guc->client[SUBMIT]);
+		guc_reset_wq(guc->client[PREEMPT]);
 	}
	err = intel_guc_sample_forcewake(guc);
 	if (err)
-		goto err_execbuf_client;
-
-	guc_reset_wq(client);
+		goto err_free_clients;
	err = guc_init_doorbell_hw(guc);
 	if (err)
-		goto err_execbuf_client;
+		goto err_free_clients;
	/* Take over from manual control of ELSP (execlists) */
 	guc_interrupts_capture(dev_priv);
@@ -1194,9 +1239,8 @@ int i915_guc_submission_enable(struct drm_i915_private *dev_priv)
	return 0;
-err_execbuf_client:
-	guc_client_free(guc->execbuf_client);
-	guc->execbuf_client = NULL;
+err_free_clients:
+	guc_clients_destroy(guc);
 	return err;
 }
@@ -1209,6 +1253,5 @@ void i915_guc_submission_disable(struct drm_i915_private *dev_priv)
 	/* Revert back to manual ELSP submission */
 	intel_engines_reset_default_submission(dev_priv);
-	guc_client_free(guc->execbuf_client);
-	guc->execbuf_client = NULL;
+	guc_clients_destroy(guc);
 }
diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index aa1583167b0a..15eadf27b7ae 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -39,6 +39,13 @@
* pool and doorbells. intel_guc owns a i915_guc_client to replace the legacy
  * ExecList submission.
  */
+
+#define I915_GUC_NUM_CLIENTS 2
+enum i915_guc_client_id {
+	SUBMIT = 0,
+	PREEMPT
+};
+
 struct intel_guc {
 	struct intel_uc_fw fw;
 	struct intel_guc_log log;
@@ -57,7 +64,7 @@ struct intel_guc {
 	struct i915_vma *shared_data;
 	void *shared_data_vaddr;
-	struct i915_guc_client *execbuf_client;
+	struct i915_guc_client *client[I915_GUC_NUM_CLIENTS];
	DECLARE_BITMAP(doorbell_bitmap, GUC_NUM_DOORBELLS);
 	/* Cyclic counter mod pagesize	*/
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 20e3c65c0999..3d91d8a28d9f 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1795,7 +1795,7 @@ bool intel_has_gpu_reset(struct drm_i915_private *dev_priv)
 bool intel_has_reset_engine(struct drm_i915_private *dev_priv)
 {
 	return (dev_priv->info.has_reset_engine &&
-		!dev_priv->guc.execbuf_client &&
+		!dev_priv->guc.client[SUBMIT] &&
 		i915_modparams.reset >= 2);
 }
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