drm/nve0: allow specification of channel engine type in abi16 call

Previously, if either vram/gart handles were specified as ~0, the ioctl
call would fail.  In order to hack engine selection into the ioctl for
kepler, we now define (fb_ctxdma_handle == ~0) to mean "engine mask is
in tt_ctxdma_handle".

This approach also allows new userspace to detect lack of support for
non-PGRAPH channels on older kernels.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_abi16.c

@@ -242,14 +242,26 @@ nouveau_abi16_ioctl_channel_alloc(ABI16_IOCTL_ARGS)
 	if (unlikely(!abi16))
 		return -ENOMEM;
 	client = nv_client(abi16->client);
-
-	if (init->fb_ctxdma_handle == ~0 || init->tt_ctxdma_handle == ~0)
-		return nouveau_abi16_put(abi16, -EINVAL);
-
 	device = nv_device(abi16->device);
 	imem   = nouveau_instmem(device);
 	pfb    = nouveau_fb(device);
 
+	/* hack to allow channel engine type specification on kepler */
+	if (device->card_type >= NV_E0) {
+		if (init->fb_ctxdma_handle != ~0)
+			init->fb_ctxdma_handle = NVE0_CHANNEL_IND_ENGINE_GR;
+		else
+			init->fb_ctxdma_handle = init->tt_ctxdma_handle;
+
+		/* allow flips to be executed if this is a graphics channel */
+		init->tt_ctxdma_handle = 0;
+		if (init->fb_ctxdma_handle == NVE0_CHANNEL_IND_ENGINE_GR)
+			init->tt_ctxdma_handle = 1;
+	}
+
+	if (init->fb_ctxdma_handle == ~0 || init->tt_ctxdma_handle == ~0)
+		return nouveau_abi16_put(abi16, -EINVAL);
+
 	/* allocate "abi16 channel" data and make up a handle for it */
 	init->channel = ffsll(~abi16->handles);
 	if (!init->channel--)
@@ -264,11 +276,6 @@ nouveau_abi16_ioctl_channel_alloc(ABI16_IOCTL_ARGS)
 	abi16->handles |= (1 << init->channel);
 
 	/* create channel object and initialise dma and fence management */
-	if (device->card_type >= NV_E0) {
-		init->fb_ctxdma_handle = NVE0_CHANNEL_IND_ENGINE_GR;
-		init->tt_ctxdma_handle = 0;
-	}
-
 	ret = nouveau_channel_new(drm, cli, NVDRM_DEVICE, NVDRM_CHAN |
 				  init->channel, init->fb_ctxdma_handle,
 				  init->tt_ctxdma_handle, &chan->chan);

drivers/gpu/drm/nouveau/nouveau_chan.c

@@ -346,7 +346,7 @@ nouveau_channel_init(struct nouveau_channel *chan, u32 vram, u32 gart)
 	/* allocate software object class (used for fences on <= nv05, and
 	 * to signal flip completion), bind it to a subchannel.
 	 */
-	if (chan != chan->drm->cechan) {
+	if ((device->card_type < NV_E0) || gart /* nve0: want_nvsw */) {
 		ret = nouveau_object_new(nv_object(client), chan->handle,
 					 NvSw, nouveau_abi16_swclass(chan->drm),
 					 NULL, 0, &object);

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -148,7 +148,7 @@ nouveau_accel_init(struct nouveau_drm *drm)
 			NV_ERROR(drm, "failed to create ce channel, %d\n", ret);
 
 		arg0 = NVE0_CHANNEL_IND_ENGINE_GR;
-		arg1 = 0;
+		arg1 = 1;
 	} else {
 		arg0 = NvDmaFB;
 		arg1 = NvDmaTT;