nouveau/firmware: using dma non-coherent interfaces for fw loading. (v2)

Currently, enabling SG_DEBUG in the kernel will cause nouveau to hit a
BUG() on startup, when the iommu is enabled:

kernel BUG at include/linux/scatterlist.h:187!
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 7 PID: 930 Comm: (udev-worker) Not tainted 6.9.0-rc3Lyude-Test+ torvalds#30
Hardware name: MSI MS-7A39/A320M GAMING PRO (MS-7A39), BIOS 1.I0 01/22/2019
RIP: 0010:sg_init_one+0x85/0xa0
Code: 69 88 32 01 83 e1 03 f6 c3 03 75 20 a8 01 75 1e 48 09 cb 41 89 54
24 08 49 89 1c 24 41 89 6c 24 0c 5b 5d 41 5c e9 7b b9 88 00 <0f> 0b 0f 0b
0f 0b 48 8b 05 5e 46 9a 01 eb b2 66 66 2e 0f 1f 84 00
RSP: 0018:ffffa776017bf6a0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffa77600d87000 RCX: 000000000000002b
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffa77680d87000
RBP: 000000000000e000 R08: 0000000000000000 R09: 0000000000000000
R10: ffff98f4c46aa508 R11: 0000000000000000 R12: ffff98f4c46aa508
R13: ffff98f4c46aa008 R14: ffffa77600d4a000 R15: ffffa77600d4a018
FS:  00007feeb5aae980(0000) GS:ffff98f5c4dc0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f22cb9a4520 CR3: 00000001043ba000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 ? die+0x36/0x90
 ? do_trap+0xdd/0x100
 ? sg_init_one+0x85/0xa0
 ? do_error_trap+0x65/0x80
 ? sg_init_one+0x85/0xa0
 ? exc_invalid_op+0x50/0x70
 ? sg_init_one+0x85/0xa0
 ? asm_exc_invalid_op+0x1a/0x20
 ? sg_init_one+0x85/0xa0
 nvkm_firmware_ctor+0x14a/0x250 [nouveau]
 nvkm_falcon_fw_ctor+0x42/0x70 [nouveau]
 ga102_gsp_booter_ctor+0xb4/0x1a0 [nouveau]
 r535_gsp_oneinit+0xb3/0x15f0 [nouveau]
 ? srso_return_thunk+0x5/0x5f
 ? srso_return_thunk+0x5/0x5f
 ? nvkm_udevice_new+0x95/0x140 [nouveau]
 ? srso_return_thunk+0x5/0x5f
 ? srso_return_thunk+0x5/0x5f
 ? ktime_get+0x47/0xb0

Fix this by using the non-coherent allocator instead, I think there
might be a better answer to this, but it involve ripping up some of
APIs using sg lists.

v2: fix build warning

Signed-off-by: Dave Airlie <airlied@redhat.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/nouveau/nvkm/core/firmware.c

@@ -205,7 +205,8 @@ nvkm_firmware_dtor(struct nvkm_firmware *fw)
 		break;
 	case NVKM_FIRMWARE_IMG_DMA:
 		nvkm_memory_unref(&memory);
-		dma_free_coherent(fw->device->dev, sg_dma_len(&fw->mem.sgl), fw->img, fw->phys);
+		dma_free_noncoherent(fw->device->dev, sg_dma_len(&fw->mem.sgl),
+				     fw->img, fw->phys, DMA_TO_DEVICE);
 		break;
 	case NVKM_FIRMWARE_IMG_SGT:
 		nvkm_memory_unref(&memory);
@@ -236,10 +237,12 @@ nvkm_firmware_ctor(const struct nvkm_firmware_func *func, const char *name,
 		break;
 	case NVKM_FIRMWARE_IMG_DMA: {
 		dma_addr_t addr;
-
 		len = ALIGN(fw->len, PAGE_SIZE);
 
-		fw->img = dma_alloc_coherent(fw->device->dev, len, &addr, GFP_KERNEL);
+		fw->img = dma_alloc_noncoherent(fw->device->dev,
+						len, &addr,
+						DMA_TO_DEVICE,
+						GFP_KERNEL);
 		if (fw->img) {
 			memcpy(fw->img, src, fw->len);
 			fw->phys = addr;

drivers/gpu/drm/nouveau/nvkm/falcon/fw.c

@@ -89,6 +89,12 @@ nvkm_falcon_fw_boot(struct nvkm_falcon_fw *fw, struct nvkm_subdev *user,
 		nvkm_falcon_fw_dtor_sigs(fw);
 	}
 
+	/* after last write to the img, sync dma mappings */
+	dma_sync_single_for_device(fw->fw.device->dev,
+				   fw->fw.phys,
+				   sg_dma_len(&fw->fw.mem.sgl),
+				   DMA_TO_DEVICE);
+
 	FLCNFW_DBG(fw, "resetting");
 	fw->func->reset(fw);