drm/v3d: Set the correct DMA mask according to the MMU's limits.

On 7278, we've got 40 bits to work with.
Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190419001014.23579-2-eric@anholt.netReviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

drivers/gpu/drm/v3d/v3d_debugfs.c

@@ -30,6 +30,7 @@ static const struct v3d_reg_def v3d_hub_reg_defs[] = {
 	REGDEF(V3D_MMU_CTL),
 	REGDEF(V3D_MMU_VIO_ADDR),
 	REGDEF(V3D_MMU_VIO_ID),
+	REGDEF(V3D_MMU_DEBUG_INFO),
 };
 
 static const struct v3d_reg_def v3d_gca_reg_defs[] = {

drivers/gpu/drm/v3d/v3d_drv.c

@@ -239,9 +239,9 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
 	struct drm_device *drm;
 	struct v3d_dev *v3d;
 	int ret;
+	u32 mmu_debug;
 	u32 ident1;
 
-	dev->coherent_dma_mask = DMA_BIT_MASK(36);
 
 	v3d = kzalloc(sizeof(*v3d), GFP_KERNEL);
 	if (!v3d)
@@ -258,6 +258,10 @@ static int v3d_platform_drm_probe(struct platform_device *pdev)
 	if (ret)
 		goto dev_free;
 
+	mmu_debug = V3D_READ(V3D_MMU_DEBUG_INFO);
+	dev->coherent_dma_mask =
+		DMA_BIT_MASK(30 + V3D_GET_FIELD(mmu_debug, V3D_MMU_PA_WIDTH));
+
 	ident1 = V3D_READ(V3D_HUB_IDENT1);
 	v3d->ver = (V3D_GET_FIELD(ident1, V3D_HUB_IDENT1_TVER) * 10 +
 		    V3D_GET_FIELD(ident1, V3D_HUB_IDENT1_REV));

drivers/gpu/drm/v3d/v3d_regs.h

@@ -191,6 +191,14 @@
 /* Address that faulted */
 #define V3D_MMU_VIO_ADDR                               0x01234
 
+#define V3D_MMU_DEBUG_INFO                             0x01238
+# define V3D_MMU_PA_WIDTH_MASK                         V3D_MASK(11, 8)
+# define V3D_MMU_PA_WIDTH_SHIFT                        8
+# define V3D_MMU_VA_WIDTH_MASK                         V3D_MASK(7, 4)
+# define V3D_MMU_VA_WIDTH_SHIFT                        4
+# define V3D_MMU_VERSION_MASK                          V3D_MASK(3, 0)
+# define V3D_MMU_VERSION_SHIFT                         0
+
 /* Per-V3D-core registers */
 
 #define V3D_CTL_IDENT0                                 0x00000