drm/nouveau/pmu: serialise send() with private mutex

nvkm_subdev.mutex is going away.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/pmu.h

@@ -18,6 +18,7 @@ struct nvkm_pmu {
 	struct completion wpr_ready;
 
 	struct {
+		struct mutex mutex;
 		u32 base;
 		u32 size;
 	} send;

drivers/gpu/drm/nouveau/nvkm/subdev/pmu/base.c

@@ -148,6 +148,7 @@ nvkm_pmu_dtor(struct nvkm_subdev *subdev)
 	nvkm_falcon_cmdq_del(&pmu->hpq);
 	nvkm_falcon_qmgr_del(&pmu->qmgr);
 	nvkm_falcon_dtor(&pmu->falcon);
+	mutex_destroy(&pmu->send.mutex);
 	return nvkm_pmu(subdev);
 }
 
@@ -168,6 +169,8 @@ nvkm_pmu_ctor(const struct nvkm_pmu_fwif *fwif, struct nvkm_device *device,
 
 	nvkm_subdev_ctor(&nvkm_pmu, device, index, &pmu->subdev);
 
+	mutex_init(&pmu->send.mutex);
+
 	INIT_WORK(&pmu->recv.work, nvkm_pmu_recv);
 	init_waitqueue_head(&pmu->recv.wait);
 

drivers/gpu/drm/nouveau/nvkm/subdev/pmu/gt215.c

@@ -34,7 +34,7 @@ gt215_pmu_send(struct nvkm_pmu *pmu, u32 reply[2],
 	struct nvkm_device *device = subdev->device;
 	u32 addr;
 
-	mutex_lock(&subdev->mutex);
+	mutex_lock(&pmu->send.mutex);
 	/* wait for a free slot in the fifo */
 	addr  = nvkm_rd32(device, 0x10a4a0);
 	if (nvkm_msec(device, 2000,
@@ -42,7 +42,7 @@ gt215_pmu_send(struct nvkm_pmu *pmu, u32 reply[2],
 		if (tmp != (addr ^ 8))
 			break;
 	) < 0) {
-		mutex_unlock(&subdev->mutex);
+		mutex_unlock(&pmu->send.mutex);
 		return -EBUSY;
 	}
 
@@ -79,7 +79,7 @@ gt215_pmu_send(struct nvkm_pmu *pmu, u32 reply[2],
 		reply[1] = pmu->recv.data[1];
 	}
 
-	mutex_unlock(&subdev->mutex);
+	mutex_unlock(&pmu->send.mutex);
 	return 0;
 }