drm/nouveau: prevent all channel creation if accel not available

Previously, if there was no firmware available, the DRM would just
disable channel creation from userspace, but still use a single
channel for its own purposes.

With a bit of care it should actually be possible to do this, due
to the DRM's very limited use of the engine.  It currently doesn't
work correctly however, resulting in corrupted fbcon and hangs on
a number of cards.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -461,11 +461,8 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict, int no_wait,
 	int ret;
 
 	chan = nvbo->channel;
-	if (!chan || nvbo->tile_flags || nvbo->no_vm) {
+	if (!chan || nvbo->tile_flags || nvbo->no_vm)
 		chan = dev_priv->channel;
-		if (!chan)
-			return -EINVAL;
-	}
 
 	src_offset = old_mem->mm_node->start << PAGE_SHIFT;
 	dst_offset = new_mem->mm_node->start << PAGE_SHIFT;
@@ -631,7 +628,8 @@ nouveau_bo_move(struct ttm_buffer_object *bo, bool evict, bool intr,
 			return ret;
 	}
 
-	if (dev_priv->init_state != NOUVEAU_CARD_INIT_DONE)
+	if (dev_priv->init_state != NOUVEAU_CARD_INIT_DONE ||
+	    !dev_priv->channel)
 		return ttm_bo_move_memcpy(bo, evict, no_wait, new_mem);
 
 	if (old_mem->mem_type == TTM_PL_SYSTEM && !bo->ttm) {

drivers/gpu/drm/nouveau/nouveau_fbcon.c

@@ -58,7 +58,7 @@ nouveau_fbcon_sync(struct fb_info *info)
 	struct nouveau_channel *chan = dev_priv->channel;
 	int ret, i;
 
-	if (!chan->accel_done ||
+	if (!chan || !chan->accel_done ||
 	    info->state != FBINFO_STATE_RUNNING ||
 	    info->flags & FBINFO_HWACCEL_DISABLED)
 		return 0;
@@ -318,6 +318,7 @@ nouveau_fbcon_create(struct drm_device *dev, uint32_t fb_width,
 	par->nouveau_fb = nouveau_fb;
 	par->dev = dev;
 
+	if (dev_priv->channel) {
 		switch (dev_priv->card_type) {
 		case NV_50:
 			nv50_fbcon_accel_init(info);
@@ -326,6 +327,7 @@ nouveau_fbcon_create(struct drm_device *dev, uint32_t fb_width,
 			nv04_fbcon_accel_init(info);
 			break;
 		};
+	}
 
 	nouveau_fbcon_zfill(dev);
 

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -299,12 +299,57 @@ nouveau_vga_set_decode(void *priv, bool state)
 		return VGA_RSRC_NORMAL_IO | VGA_RSRC_NORMAL_MEM;
 }
 
+static int
+nouveau_card_init_channel(struct drm_device *dev)
+{
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	struct nouveau_gpuobj *gpuobj;
+	int ret;
+
+	ret = nouveau_channel_alloc(dev, &dev_priv->channel,
+				    (struct drm_file *)-2,
+				    NvDmaFB, NvDmaTT);
+	if (ret)
+		return ret;
+
+	gpuobj = NULL;
+	ret = nouveau_gpuobj_dma_new(dev_priv->channel, NV_CLASS_DMA_IN_MEMORY,
+				     0, nouveau_mem_fb_amount(dev),
+				     NV_DMA_ACCESS_RW, NV_DMA_TARGET_VIDMEM,
+				     &gpuobj);
+	if (ret)
+		goto out_err;
+
+	ret = nouveau_gpuobj_ref_add(dev, dev_priv->channel, NvDmaVRAM,
+				     gpuobj, NULL);
+	if (ret)
+		goto out_err;
+
+	gpuobj = NULL;
+	ret = nouveau_gpuobj_gart_dma_new(dev_priv->channel, 0,
+					  dev_priv->gart_info.aper_size,
+					  NV_DMA_ACCESS_RW, &gpuobj, NULL);
+	if (ret)
+		goto out_err;
+
+	ret = nouveau_gpuobj_ref_add(dev, dev_priv->channel, NvDmaGART,
+				     gpuobj, NULL);
+	if (ret)
+		goto out_err;
+
+	return 0;
+out_err:
+	nouveau_gpuobj_del(dev, &gpuobj);
+	nouveau_channel_free(dev_priv->channel);
+	dev_priv->channel = NULL;
+	return ret;
+}
+
 int
 nouveau_card_init(struct drm_device *dev)
 {
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_engine *engine;
-	struct nouveau_gpuobj *gpuobj;
 	int ret;
 
 	NV_DEBUG(dev, "prev state = %d\n", dev_priv->init_state);
@@ -387,39 +432,10 @@ nouveau_card_init(struct drm_device *dev)
 
 	/* what about PVIDEO/PCRTC/PRAMDAC etc? */
 
-	ret = nouveau_channel_alloc(dev, &dev_priv->channel,
-				    (struct drm_file *)-2,
-				    NvDmaFB, NvDmaTT);
-	if (ret)
-		goto out_irq;
-
-	gpuobj = NULL;
-	ret = nouveau_gpuobj_dma_new(dev_priv->channel, NV_CLASS_DMA_IN_MEMORY,
-				     0, nouveau_mem_fb_amount(dev),
-				     NV_DMA_ACCESS_RW, NV_DMA_TARGET_VIDMEM,
-				     &gpuobj);
-	if (ret)
-		goto out_irq;
-
-	ret = nouveau_gpuobj_ref_add(dev, dev_priv->channel, NvDmaVRAM,
-				     gpuobj, NULL);
-	if (ret) {
-		nouveau_gpuobj_del(dev, &gpuobj);
-		goto out_irq;
-	}
-
-	gpuobj = NULL;
-	ret = nouveau_gpuobj_gart_dma_new(dev_priv->channel, 0,
-					  dev_priv->gart_info.aper_size,
-					  NV_DMA_ACCESS_RW, &gpuobj, NULL);
+	if (!engine->graph.accel_blocked) {
+		ret = nouveau_card_init_channel(dev);
 		if (ret)
 			goto out_irq;
-
-	ret = nouveau_gpuobj_ref_add(dev, dev_priv->channel, NvDmaGART,
-				     gpuobj, NULL);
-	if (ret) {
-		nouveau_gpuobj_del(dev, &gpuobj);
-		goto out_irq;
 	}
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {