make RAM device optional

Having a RAM device does not make sense for chips like GK20A which have
no dedicated video memory. The dummy RAM device that we used so far
works as a temporary band-aid, but in the longer term it is desirable
for the driver to be able to work without any kind of VRAM.

This patch adds a few conditionals in places where a RAM device was
assumed to be present and allows some more objects to be allocated from
the TT domain, allowing Nouveau to handle GPUs for which
pfb->ram == NULL.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_display.c

@@ -869,13 +869,20 @@ nouveau_display_dumb_create(struct drm_file *file_priv, struct drm_device *dev,
 			    struct drm_mode_create_dumb *args)
 {
 	struct nouveau_bo *bo;
+	uint32_t domain;
 	int ret;
 
 	args->pitch = roundup(args->width * (args->bpp / 8), 256);
 	args->size = args->pitch * args->height;
 	args->size = roundup(args->size, PAGE_SIZE);
 
-	ret = nouveau_gem_new(dev, args->size, 0, NOUVEAU_GEM_DOMAIN_VRAM, 0, 0, &bo);
+	/* Use VRAM if there is any ; otherwise fallback to system memory */
+	if (nouveau_drm(dev)->device.info.ram_size != 0)
+		domain = NOUVEAU_GEM_DOMAIN_VRAM;
+	else
+		domain = NOUVEAU_GEM_DOMAIN_GART;
+
+	ret = nouveau_gem_new(dev, args->size, 0, domain, 0, 0, &bo);
 	if (ret)
 		return ret;
 

drivers/gpu/drm/nouveau/nouveau_ttm.c

@@ -82,6 +82,9 @@ nouveau_vram_manager_new(struct ttm_mem_type_manager *man,
 	u32 size_nc = 0;
 	int ret;
 
+	if (drm->device.info.ram_size == 0)
+		return -ENOMEM;
+
 	if (nvbo->tile_flags & NOUVEAU_GEM_TILE_NONCONTIG)
 		size_nc = 1 << nvbo->page_shift;
 

drivers/gpu/drm/nouveau/nv84_fence.c

@@ -215,6 +215,7 @@ nv84_fence_create(struct nouveau_drm *drm)
 {
 	struct nvkm_fifo *pfifo = nvxx_fifo(&drm->device);
 	struct nv84_fence_priv *priv;
+	u32 domain;
 	int ret;
 
 	priv = drm->fence = kzalloc(sizeof(*priv), GFP_KERNEL);
@@ -231,10 +232,17 @@ nv84_fence_create(struct nouveau_drm *drm)
 	priv->base.context_base = fence_context_alloc(priv->base.contexts);
 	priv->base.uevent = true;
 
-	ret = nouveau_bo_new(drm->dev, 16 * priv->base.contexts, 0,
-			     TTM_PL_FLAG_VRAM, 0, 0, NULL, NULL, &priv->bo);
+	/* Use VRAM if there is any ; otherwise fallback to system memory */
+	domain = drm->device.info.ram_size != 0 ? TTM_PL_FLAG_VRAM :
+			 /*
+			  * fences created in sysmem must be non-cached or we
+			  * will lose CPU/GPU coherency!
+			  */
+			 TTM_PL_FLAG_TT | TTM_PL_FLAG_UNCACHED;
+	ret = nouveau_bo_new(drm->dev, 16 * priv->base.contexts, 0, domain, 0,
+			     0, NULL, NULL, &priv->bo);
 	if (ret == 0) {
-		ret = nouveau_bo_pin(priv->bo, TTM_PL_FLAG_VRAM, false);
+		ret = nouveau_bo_pin(priv->bo, domain, false);
 		if (ret == 0) {
 			ret = nouveau_bo_map(priv->bo);
 			if (ret)

drivers/gpu/drm/nouveau/nvkm/engine/device/base.c

@@ -139,9 +139,13 @@ nvkm_devobj_info(struct nvkm_object *object, void *data, u32 size)
 
 	args->v0.chipset  = device->chipset;
 	args->v0.revision = device->chiprev;
-	if (pfb)  args->v0.ram_size = args->v0.ram_user = pfb->ram->size;
-	else      args->v0.ram_size = args->v0.ram_user = 0;
-	if (imem) args->v0.ram_user = args->v0.ram_user - imem->reserved;
+	if (pfb && pfb->ram)
+		args->v0.ram_size = args->v0.ram_user = pfb->ram->size;
+	else
+		args->v0.ram_size = args->v0.ram_user = 0;
+	if (imem && args->v0.ram_size > 0)
+		args->v0.ram_user = args->v0.ram_user - imem->reserved;
+
 	return 0;
 }
 

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

@@ -184,7 +184,7 @@ nvkm_pstate_prog(struct nvkm_clk *clk, int pstatei)
 	nv_debug(clk, "setting performance state %d\n", pstatei);
 	clk->pstate = pstatei;
 
-	if (pfb->ram->calc) {
+	if (pfb->ram && pfb->ram->calc) {
 		int khz = pstate->base.domain[nv_clk_src_mem];
 		do {
 			ret = pfb->ram->calc(pfb, khz);

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

@@ -55,9 +55,11 @@ _nvkm_fb_fini(struct nvkm_object *object, bool suspend)
 	struct nvkm_fb *pfb = (void *)object;
 	int ret;
 
-	ret = nv_ofuncs(pfb->ram)->fini(nv_object(pfb->ram), suspend);
-	if (ret && suspend)
-		return ret;
+	if (pfb->ram) {
+		ret = nv_ofuncs(pfb->ram)->fini(nv_object(pfb->ram), suspend);
+		if (ret && suspend)
+			return ret;
+	}
 
 	return nvkm_subdev_fini(&pfb->base, suspend);
 }
@@ -72,9 +74,11 @@ _nvkm_fb_init(struct nvkm_object *object)
 	if (ret)
 		return ret;
 
-	ret = nv_ofuncs(pfb->ram)->init(nv_object(pfb->ram));
-	if (ret)
-		return ret;
+	if (pfb->ram) {
+		ret = nv_ofuncs(pfb->ram)->init(nv_object(pfb->ram));
+		if (ret)
+			return ret;
+	}
 
 	for (i = 0; i < pfb->tile.regions; i++)
 		pfb->tile.prog(pfb, i, &pfb->tile.region[i]);
@@ -91,9 +95,12 @@ _nvkm_fb_dtor(struct nvkm_object *object)
 	for (i = 0; i < pfb->tile.regions; i++)
 		pfb->tile.fini(pfb, i, &pfb->tile.region[i]);
 	nvkm_mm_fini(&pfb->tags);
-	nvkm_mm_fini(&pfb->vram);
 
-	nvkm_object_ref(NULL, (struct nvkm_object **)&pfb->ram);
+	if (pfb->ram) {
+		nvkm_mm_fini(&pfb->vram);
+		nvkm_object_ref(NULL, (struct nvkm_object **)&pfb->ram);
+	}
+
 	nvkm_subdev_destroy(&pfb->base);
 }
 
@@ -127,6 +134,9 @@ nvkm_fb_create_(struct nvkm_object *parent, struct nvkm_object *engine,
 
 	pfb->memtype_valid = impl->memtype;
 
+	if (!impl->ram)
+		return 0;
+
 	ret = nvkm_object_ctor(nv_object(pfb), NULL, impl->ram, NULL, 0, &ram);
 	if (ret) {
 		nv_fatal(pfb, "error detecting memory configuration!!\n");

drivers/gpu/drm/nouveau/nvkm/subdev/ltc/gf100.c

@@ -136,7 +136,8 @@ gf100_ltc_dtor(struct nvkm_object *object)
 	struct nvkm_ltc_priv *priv = (void *)object;
 
 	nvkm_mm_fini(&priv->tags);
-	nvkm_mm_free(&pfb->vram, &priv->tag_ram);
+	if (pfb->ram)
+		nvkm_mm_free(&pfb->vram, &priv->tag_ram);
 
 	nvkm_ltc_destroy(priv);
 }
@@ -149,6 +150,12 @@ gf100_ltc_init_tag_ram(struct nvkm_fb *pfb, struct nvkm_ltc_priv *priv)
 	u32 tag_size, tag_margin, tag_align;
 	int ret;
 
+	/* No VRAM, no tags for now. */
+	if (!pfb->ram) {
+		priv->num_tags = 0;
+		goto mm_init;
+	}
+
 	/* tags for 1/4 of VRAM should be enough (8192/4 per GiB of VRAM) */
 	priv->num_tags = (pfb->ram->size >> 17) / 4;
 	if (priv->num_tags > (1 << 17))
@@ -183,6 +190,7 @@ gf100_ltc_init_tag_ram(struct nvkm_fb *pfb, struct nvkm_ltc_priv *priv)
 		priv->tag_base = tag_base;
 	}
 
+mm_init:
 	ret = nvkm_mm_init(&priv->tags, 0, priv->num_tags, 1);
 	return ret;
 }