drm/msm/a6xx: Add a flag to allow preemption to submitqueue_create

Some userspace changes are necessary so add a flag for userspace to
advertise support for preemption when creating the submitqueue.

When this flag is not set preemption will not be allowed in the middle
of the submitted IBs therefore mantaining compatibility with older
userspace.

The flag is rejected if preemption is not supported on the target, this
allows userspace to know whether preemption is supported.

Tested-by: Rob Clark <[e-mail]>
Tested-by: Neil Armstrong <[e-mail]> # on SM8650-QRD
Tested-by: Neil Armstrong <[e-mail]> # on SM8550-QRD
Tested-by: Neil Armstrong <[e-mail]> # on SM8450-HDK
Signed-off-by: Antonino Maniscalco <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/618028/
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

···
 	OUT_PKT7(ring, CP_SET_MARKER, 1);
 	OUT_RING(ring, 0x101); /* IFPC disable */
 
-	OUT_PKT7(ring, CP_SET_MARKER, 1);
-	OUT_RING(ring, 0x00d); /* IB1LIST start */
+	if (submit->queue->flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT) {
+		OUT_PKT7(ring, CP_SET_MARKER, 1);
+		OUT_RING(ring, 0x00d); /* IB1LIST start */
+	}
 
 	/* Submit the commands */
 	for (i = 0; i < submit->nr_cmds; i++) {
···
 			update_shadow_rptr(gpu, ring);
 	}
 
-	OUT_PKT7(ring, CP_SET_MARKER, 1);
-	OUT_RING(ring, 0x00e); /* IB1LIST end */
+	if (submit->queue->flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT) {
+		OUT_PKT7(ring, CP_SET_MARKER, 1);
+		OUT_RING(ring, 0x00e); /* IB1LIST end */
+	}
 
 	get_stats_counter(ring, REG_A7XX_RBBM_PERFCTR_CP(0),
 		rbmemptr_stats(ring, index, cpcycles_end));

drivers/gpu/drm/msm/msm_submitqueue.c

···
 	if (!priv->gpu)
 		return -ENODEV;
 
+	if (flags & MSM_SUBMITQUEUE_ALLOW_PREEMPT && priv->gpu->nr_rings == 1)
+		return -EINVAL;
+
 	ret = msm_gpu_convert_priority(priv->gpu, prio, &ring_nr, &sched_prio);
 	if (ret)
 		return ret;

include/uapi/drm/msm_drm.h

···
  * backwards compatibility as a "default" submitqueue
  */
 
-#define MSM_SUBMITQUEUE_FLAGS (0)
+#define MSM_SUBMITQUEUE_ALLOW_PREEMPT	0x00000001
+#define MSM_SUBMITQUEUE_FLAGS		    ( \
+		MSM_SUBMITQUEUE_ALLOW_PREEMPT | \
+		0)
 
 /*
  * The submitqueue priority should be between 0 and MSM_PARAM_PRIORITIES-1,