drm/i915/guc: replace assign_doorbell() with select_doorbell_register()

This version doesn't update the doorbell bitmap, as that will
be done when the selected doorbell is associated with a client.

The call is now slightly earlier, just on the general principle
that potentially-failing operations should be done as early as
possible, to eliminate late failures and simplify recovery.

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 62bf4bd..a252505 100644 (file)
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -232,6 +232,32 @@ static void guc_disable_doorbell(struct intel_guc *guc,
        /* XXX: wait for workqueue to drain */
 }
 
+static uint16_t
+select_doorbell_register(struct intel_guc *guc, uint32_t priority)
+{
+       /*
+        * The bitmap tracks which doorbell registers are currently in use.
+        * It is split into two halves; the first half is used for normal
+        * priority contexts, the second half for high-priority ones.
+        * Note that logically higher priorities are numerically less than
+        * normal ones, so the test below means "is it high-priority?"
+        */
+       const bool hi_pri = (priority <= GUC_CTX_PRIORITY_HIGH);
+       const uint16_t half = GUC_MAX_DOORBELLS / 2;
+       const uint16_t start = hi_pri ? half : 0;
+       const uint16_t end = start + half;
+       uint16_t id;
+
+       id = find_next_zero_bit(guc->doorbell_bitmap, end, start);
+       if (id == end)
+               id = GUC_INVALID_DOORBELL_ID;
+
+       DRM_DEBUG_DRIVER("assigned %s priority doorbell id 0x%x\n",
+                       hi_pri ? "high" : "normal", id);
+
+       return id;
+}
+
 /*
  * Select, assign and relase doorbell cachelines
  *
@@ -256,32 +282,6 @@ static uint32_t select_doorbell_cacheline(struct intel_guc *guc)
        return offset;
 }
 
-static uint16_t assign_doorbell(struct intel_guc *guc, uint32_t priority)
-{
-       /*
-        * The bitmap is split into two halves; the first half is used for
-        * normal priority contexts, the second half for high-priority ones.
-        * Note that logically higher priorities are numerically less than
-        * normal ones, so the test below means "is it high-priority?"
-        */
-       const bool hi_pri = (priority <= GUC_CTX_PRIORITY_HIGH);
-       const uint16_t half = GUC_MAX_DOORBELLS / 2;
-       const uint16_t start = hi_pri ? half : 0;
-       const uint16_t end = start + half;
-       uint16_t id;
-
-       id = find_next_zero_bit(guc->doorbell_bitmap, end, start);
-       if (id == end)
-               id = GUC_INVALID_DOORBELL_ID;
-       else
-               __set_bit(id, guc->doorbell_bitmap);
-
-       DRM_DEBUG_DRIVER("assigned %s priority doorbell id 0x%x\n",
-                       hi_pri ? "high" : "normal", id);
-
-       return id;
-}
-
 /*
  * Initialise the process descriptor shared with the GuC firmware.
  */
@@ -742,6 +742,11 @@ guc_client_alloc(struct drm_i915_private *dev_priv,
        client->wq_offset = GUC_DB_SIZE;
        client->wq_size = GUC_WQ_SIZE;
 
+       db_id = select_doorbell_register(guc, client->priority);
+       if (db_id == GUC_INVALID_DOORBELL_ID)
+               /* XXX: evict a doorbell instead? */
+               goto err;
+
        client->doorbell_offset = select_doorbell_cacheline(guc);
 
        /*
@@ -754,11 +759,6 @@ guc_client_alloc(struct drm_i915_private *dev_priv,
        else
                client->proc_desc_offset = (GUC_DB_SIZE / 2);
 
-       db_id = assign_doorbell(guc, client->priority);
-       if (db_id == GUC_INVALID_DOORBELL_ID)
-               /* XXX: evict a doorbell instead */
-               goto err;
-
        guc_init_proc_desc(guc, client);
        guc_init_ctx_desc(guc, client);
        if (guc_init_doorbell(guc, client, db_id))