[PATCH 4.4 17/58] drm/nouveau/fifo/gf100-: protect channel preempt with subdev mutex

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Skeggs <bskeggs@redhat.com>

commit b27add13f500469127afdf011dbcc9c649e16e54 upstream.

This avoids an issue that occurs when we're attempting to preempt multiple
channels simultaneously.  HW seems to ignore preempt requests while it's
still processing a previous one, which, well, makes sense.

Fixes random "fifo: SCHED_ERROR 0d []" + GPCCS page faults during parallel
piglit runs on (at least) GM107.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogf100.c |    9 ++++++---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogk104.c |    8 +++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogf100.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogf100.c
@@ -59,6 +59,7 @@ gf100_fifo_gpfifo_engine_fini(struct nvk
 	struct nvkm_gpuobj *inst = chan->base.inst;
 	int ret = 0;
 
+	mutex_lock(&subdev->mutex);
 	nvkm_wr32(device, 0x002634, chan->base.chid);
 	if (nvkm_msec(device, 2000,
 		if (nvkm_rd32(device, 0x002634) == chan->base.chid)
@@ -66,10 +67,12 @@ gf100_fifo_gpfifo_engine_fini(struct nvk
 	) < 0) {
 		nvkm_error(subdev, "channel %d [%s] kick timeout\n",
 			   chan->base.chid, chan->base.object.client->name);
-		ret = -EBUSY;
-		if (suspend)
-			return ret;
+		ret = -ETIMEDOUT;
 	}
+	mutex_unlock(&subdev->mutex);
+
+	if (ret && suspend)
+		return ret;
 
 	if (offset) {
 		nvkm_kmap(inst);
--- a/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogk104.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogk104.c
@@ -39,7 +39,9 @@ gk104_fifo_gpfifo_kick(struct gk104_fifo
 	struct nvkm_subdev *subdev = &fifo->base.engine.subdev;
 	struct nvkm_device *device = subdev->device;
 	struct nvkm_client *client = chan->base.object.client;
+	int ret = 0;
 
+	mutex_lock(&subdev->mutex);
 	nvkm_wr32(device, 0x002634, chan->base.chid);
 	if (nvkm_msec(device, 2000,
 		if (!(nvkm_rd32(device, 0x002634) & 0x00100000))
@@ -47,10 +49,10 @@ gk104_fifo_gpfifo_kick(struct gk104_fifo
 	) < 0) {
 		nvkm_error(subdev, "channel %d [%s] kick timeout\n",
 			   chan->base.chid, client->name);
-		return -EBUSY;
+		ret = -ETIMEDOUT;
 	}
-
-	return 0;
+	mutex_unlock(&subdev->mutex);
+	return ret;
 }
 
 static u32