drm/msm: Utilize gpu scheduler priorities

The drm/scheduler provides additional prioritization on top of that
provided by however many number of ringbuffers (each with their own
priority level) is supported on a given generation.  Expose the
additional levels of priority to userspace and map the userspace
priority back to ring (first level of priority) and schedular priority
(additional priority levels within the ring).

Signed-off-by: Rob Clark <robdclark@chromium.org>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20210728010632.2633470-13-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 56 insertions, 2 deletions

diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
index b912cacaecc0..0e4b45bff2e6 100644
--- a/drivers/gpu/drm/msm/msm_gpu.h
+++ b/drivers/gpu/drm/msm/msm_gpu.h
@@ -250,6 +250,59 @@ struct msm_gpu_perfcntr {
 	const char *name;
 };
 
+/*
+ * The number of priority levels provided by drm gpu scheduler.  The
+ * DRM_SCHED_PRIORITY_KERNEL priority level is treated specially in some
+ * cases, so we don't use it (no need for kernel generated jobs).
+ */
+#define NR_SCHED_PRIORITIES (1 + DRM_SCHED_PRIORITY_HIGH - DRM_SCHED_PRIORITY_MIN)
+
+/**
+ * msm_gpu_convert_priority - Map userspace priority to ring # and sched priority
+ *
+ * @gpu:        the gpu instance
+ * @prio:       the userspace priority level
+ * @ring_nr:    [out] the ringbuffer the userspace priority maps to
+ * @sched_prio: [out] the gpu scheduler priority level which the userspace
+ *              priority maps to
+ *
+ * With drm/scheduler providing it's own level of prioritization, our total
+ * number of available priority levels is (nr_rings * NR_SCHED_PRIORITIES).
+ * Each ring is associated with it's own scheduler instance.  However, our
+ * UABI is that lower numerical values are higher priority.  So mapping the
+ * single userspace priority level into ring_nr and sched_prio takes some
+ * care.  The userspace provided priority (when a submitqueue is created)
+ * is mapped to ring nr and scheduler priority as such:
+ *
+ *   ring_nr    = userspace_prio / NR_SCHED_PRIORITIES
+ *   sched_prio = NR_SCHED_PRIORITIES -
+ *                (userspace_prio % NR_SCHED_PRIORITIES) - 1
+ *
+ * This allows generations without preemption (nr_rings==1) to have some
+ * amount of prioritization, and provides more priority levels for gens
+ * that do have preemption.
+ */
+static inline int msm_gpu_convert_priority(struct msm_gpu *gpu, int prio,
+		unsigned *ring_nr, enum drm_sched_priority *sched_prio)
+{
+	unsigned rn, sp;
+
+	rn = div_u64_rem(prio, NR_SCHED_PRIORITIES, &sp);
+
+	/* invert sched priority to map to higher-numeric-is-higher-
+	 * priority convention
+	 */
+	sp = NR_SCHED_PRIORITIES - sp - 1;
+
+	if (rn >= gpu->nr_rings)
+		return -EINVAL;
+
+	*ring_nr = rn;
+	*sched_prio = sp;
+
+	return 0;
+}
+
 /**
  * A submitqueue is associated with a gl context or vk queue (or equiv)
  * in userspace.
@@ -257,7 +310,8 @@ struct msm_gpu_perfcntr {
  * @id:        userspace id for the submitqueue, unique within the drm_file
  * @flags:     userspace flags for the submitqueue, specified at creation
  *             (currently unusued)
- * @prio:      the submitqueue priority
+ * @ring_nr:   the ringbuffer used by this submitqueue, which is determined
+ *             by the submitqueue's priority
  * @faults:    the number of GPU hangs associated with this submitqueue
  * @ctx:       the per-drm_file context associated with the submitqueue (ie.
  *             which set of pgtables do submits jobs associated with the
@@ -272,7 +326,7 @@ struct msm_gpu_perfcntr {
 struct msm_gpu_submitqueue {
 	int id;
 	u32 flags;
-	u32 prio;
+	u32 ring_nr;
 	int faults;
 	struct msm_file_private *ctx;
 	struct list_head node;