[PATCH] drm/i915: Flip guc_id allocation partition

[Matthew Brost]

Move the multi-lrc guc_id from the lower allocation partition (0 to
number of multi-lrc guc_ids) to upper allocation partition (number of
single-lrc to max guc_ids).

This will help when a native driver transitions to a PF after driver
load time. If the perma-pin guc_ids (kernel contexts) are in a low range
it is easy reduce total number of guc_ids as the allocated slrc are in a
valid range the mlrc range moves to an unused range. Assuming no mlrc
are allocated and few slrc are used the native to PF transition is
seamless for the guc_id resource.

v2:
 (Michal / Tvrtko)
  - Add an explaination to commit message of why this patch is needed
 (Michal / Piotr)
  - Replace marcos with functions
 (Michal)
  - Rework logic flow in new_mlrc_guc_id
  - Unconditionally call bitmap_free

Signed-off-by: Matthew Brost <matthew.brost at intel.com>
---
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 88 +++++++++++++------
 1 file changed, 63 insertions(+), 25 deletions(-)

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 23a40f10d376d..3ae92260f8224 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -138,17 +138,6 @@ guc_create_parallel(struct intel_engine_cs **engines,
 
 #define GUC_REQUEST_SIZE 64 /* bytes */
 
-/*
- * We reserve 1/16 of the guc_ids for multi-lrc as these need to be contiguous
- * per the GuC submission interface. A different allocation algorithm is used
- * (bitmap vs. ida) between multi-lrc and single-lrc hence the reason to
- * partition the guc_id space. We believe the number of multi-lrc contexts in
- * use should be low and 1/16 should be sufficient. Minimum of 32 guc_ids for
- * multi-lrc.
- */
-#define NUMBER_MULTI_LRC_GUC_ID(guc)	\
-	((guc)->submission_state.num_guc_ids / 16)
-
 /*
  * Below is a set of functions which control the GuC scheduling state which
  * require a lock.
@@ -1777,11 +1766,6 @@ int intel_guc_submission_init(struct intel_guc *guc)
 	INIT_WORK(&guc->submission_state.destroyed_worker,
 		  destroyed_worker_func);
 
-	guc->submission_state.guc_ids_bitmap =
-		bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID(guc), GFP_KERNEL);
-	if (!guc->submission_state.guc_ids_bitmap)
-		return -ENOMEM;
-
 	spin_lock_init(&guc->timestamp.lock);
 	INIT_DELAYED_WORK(&guc->timestamp.work, guc_timestamp_ping);
 	guc->timestamp.ping_delay = (POLL_TIME_CLKS / gt->clock_frequency + 1) * HZ;
@@ -1864,6 +1848,57 @@ static void guc_submit_request(struct i915_request *rq)
 	spin_unlock_irqrestore(&sched_engine->lock, flags);
 }
 
+/*
+ * We reserve 1/16 of the guc_ids for multi-lrc as these need to be contiguous
+ * per the GuC submission interface. A different allocation algorithm is used
+ * (bitmap vs. ida) between multi-lrc and single-lrc hence the reason to
+ * partition the guc_id space. We believe the number of multi-lrc contexts in
+ * use should be low and 1/16 should be sufficient.
+ */
+#define MLRC_GUC_ID_RATIO	16
+
+static int number_mlrc_guc_id(struct intel_guc *guc)
+{
+	return guc->submission_state.num_guc_ids / MLRC_GUC_ID_RATIO;
+}
+
+static int number_slrc_guc_id(struct intel_guc *guc)
+{
+	return guc->submission_state.num_guc_ids - number_mlrc_guc_id(guc);
+}
+
+static int mlrc_guc_id_base(struct intel_guc *guc)
+{
+	return number_slrc_guc_id(guc);
+}
+
+static int new_mlrc_guc_id(struct intel_guc *guc, struct intel_context *ce)
+{
+	int ret;
+
+	GEM_BUG_ON(!intel_context_is_parent(ce));
+	GEM_BUG_ON(!guc->submission_state.guc_ids_bitmap);
+
+	ret =  bitmap_find_free_region(guc->submission_state.guc_ids_bitmap,
+				       number_mlrc_guc_id(guc),
+				       order_base_2(ce->parallel.number_children
+						    + 1));
+	if (unlikely(ret < 0))
+		return ret;
+
+	return ret + mlrc_guc_id_base(guc);
+}
+
+static int new_slrc_guc_id(struct intel_guc *guc, struct intel_context *ce)
+{
+	GEM_BUG_ON(intel_context_is_parent(ce));
+
+	return ida_simple_get(&guc->submission_state.guc_ids,
+			      0, number_slrc_guc_id(guc),
+			      GFP_KERNEL | __GFP_RETRY_MAYFAIL |
+			      __GFP_NOWARN);
+}
+
 static int new_guc_id(struct intel_guc *guc, struct intel_context *ce)
 {
 	int ret;
@@ -1871,16 +1906,10 @@ static int new_guc_id(struct intel_guc *guc, struct intel_context *ce)
 	GEM_BUG_ON(intel_context_is_child(ce));
 
 	if (intel_context_is_parent(ce))
-		ret = bitmap_find_free_region(guc->submission_state.guc_ids_bitmap,
-					      NUMBER_MULTI_LRC_GUC_ID(guc),
-					      order_base_2(ce->parallel.number_children
-							   + 1));
+		ret = new_mlrc_guc_id(guc, ce);
 	else
-		ret = ida_simple_get(&guc->submission_state.guc_ids,
-				     NUMBER_MULTI_LRC_GUC_ID(guc),
-				     guc->submission_state.num_guc_ids,
-				     GFP_KERNEL | __GFP_RETRY_MAYFAIL |
-				     __GFP_NOWARN);
+		ret = new_slrc_guc_id(guc, ce);
+
 	if (unlikely(ret < 0))
 		return ret;
 
@@ -1990,6 +2019,15 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
 
 	GEM_BUG_ON(atomic_read(&ce->guc_id.ref));
 
+	/* Outside spin lock so we can sleep on alloc */
+	if (unlikely(intel_context_is_parent(ce) &&
+		     !guc->submission_state.guc_ids_bitmap)) {
+		guc->submission_state.guc_ids_bitmap =
+			bitmap_zalloc(number_mlrc_guc_id(guc), GFP_KERNEL);
+		if (!guc->submission_state.guc_ids_bitmap)
+			return -ENOMEM;
+	}
+
 try_again:
 	spin_lock_irqsave(&guc->submission_state.lock, flags);
 
-- 
2.34.1