drm/nouveau: protect channel create/destroy and irq handler with a spinlock

The nv50 pgraph handler (for example) could reenable pgraph fifo access
and that would be bad when pgraph context is being unloaded (we need the
guarantee a ctxprog isn't running).
Signed-off-by: Maarten Maathuis <madman2003@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_channel.c

@@ -275,9 +275,18 @@ nouveau_channel_free(struct nouveau_channel *chan)
 	 */
 	nouveau_fence_fini(chan);
 
-	/* Ensure the channel is no longer active on the GPU */
+	/* This will prevent pfifo from switching channels. */
 	pfifo->reassign(dev, false);
 
+	/* We want to give pgraph a chance to idle and get rid of all potential
+	 * errors. We need to do this before the lock, otherwise the irq handler
+	 * is unable to process them.
+	 */
+	if (pgraph->channel(dev) == chan)
+		nouveau_wait_for_idle(dev);
+
+	spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
+
 	pgraph->fifo_access(dev, false);
 	if (pgraph->channel(dev) == chan)
 		pgraph->unload_context(dev);
@@ -293,6 +302,8 @@ nouveau_channel_free(struct nouveau_channel *chan)
 
 	pfifo->reassign(dev, true);
 
+	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
+
 	/* Release the channel's resources */
 	nouveau_gpuobj_ref_del(dev, &chan->pushbuf);
 	if (chan->pushbuf_bo) {

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -533,6 +533,9 @@ struct drm_nouveau_private {
 	struct nouveau_engine engine;
 	struct nouveau_channel *channel;
 
+	/* For PFIFO and PGRAPH. */
+	spinlock_t context_switch_lock;
+
 	/* RAMIN configuration, RAMFC, RAMHT and RAMRO offsets */
 	struct nouveau_gpuobj *ramht;
 	uint32_t ramin_rsvd_vram;

drivers/gpu/drm/nouveau/nouveau_irq.c

@@ -691,11 +691,14 @@ nouveau_irq_handler(DRM_IRQ_ARGS)
 	struct drm_device *dev = (struct drm_device *)arg;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	uint32_t status, fbdev_flags = 0;
+	unsigned long flags;
 
 	status = nv_rd32(dev, NV03_PMC_INTR_0);
 	if (!status)
 		return IRQ_NONE;
 
+	spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
+
 	if (dev_priv->fbdev_info) {
 		fbdev_flags = dev_priv->fbdev_info->flags;
 		dev_priv->fbdev_info->flags |= FBINFO_HWACCEL_DISABLED;
@@ -733,5 +736,7 @@ nouveau_irq_handler(DRM_IRQ_ARGS)
 	if (dev_priv->fbdev_info)
 		dev_priv->fbdev_info->flags = fbdev_flags;
 
+	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
+
 	return IRQ_HANDLED;
 }

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -391,6 +391,7 @@ nouveau_card_init(struct drm_device *dev)
 		goto out;
 	engine = &dev_priv->engine;
 	dev_priv->init_state = NOUVEAU_CARD_INIT_FAILED;
+	spin_lock_init(&dev_priv->context_switch_lock);
 
 	/* Parse BIOS tables / Run init tables if card not POSTed */
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {

drivers/gpu/drm/nouveau/nv04_fifo.c

@@ -117,6 +117,7 @@ nv04_fifo_create_context(struct nouveau_channel *chan)
 {
 	struct drm_device *dev = chan->dev;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
+	unsigned long flags;
 	int ret;
 
 	ret = nouveau_gpuobj_new_fake(dev, NV04_RAMFC(chan->id), ~0,
@@ -127,6 +128,8 @@ nv04_fifo_create_context(struct nouveau_channel *chan)
 	if (ret)
 		return ret;
 
+	spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
+
 	/* Setup initial state */
 	dev_priv->engine.instmem.prepare_access(dev, true);
 	RAMFC_WR(DMA_PUT, chan->pushbuf_base);
@@ -144,6 +147,8 @@ nv04_fifo_create_context(struct nouveau_channel *chan)
 	/* enable the fifo dma operation */
 	nv_wr32(dev, NV04_PFIFO_MODE,
 		nv_rd32(dev, NV04_PFIFO_MODE) | (1 << chan->id));
+
+	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 	return 0;
 }
 

drivers/gpu/drm/nouveau/nv40_fifo.c

@@ -37,6 +37,7 @@ nv40_fifo_create_context(struct nouveau_channel *chan)
 	struct drm_device *dev = chan->dev;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	uint32_t fc = NV40_RAMFC(chan->id);
+	unsigned long flags;
 	int ret;
 
 	ret = nouveau_gpuobj_new_fake(dev, NV40_RAMFC(chan->id), ~0,
@@ -45,6 +46,8 @@ nv40_fifo_create_context(struct nouveau_channel *chan)
 	if (ret)
 		return ret;
 
+	spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
+
 	dev_priv->engine.instmem.prepare_access(dev, true);
 	nv_wi32(dev, fc +  0, chan->pushbuf_base);
 	nv_wi32(dev, fc +  4, chan->pushbuf_base);
@@ -63,6 +66,8 @@ nv40_fifo_create_context(struct nouveau_channel *chan)
 	/* enable the fifo dma operation */
 	nv_wr32(dev, NV04_PFIFO_MODE,
 		nv_rd32(dev, NV04_PFIFO_MODE) | (1 << chan->id));
+
+	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 	return 0;
 }
 

drivers/gpu/drm/nouveau/nv50_fifo.c

@@ -243,6 +243,7 @@ nv50_fifo_create_context(struct nouveau_channel *chan)
 	struct drm_device *dev = chan->dev;
 	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_gpuobj *ramfc = NULL;
+	unsigned long flags;
 	int ret;
 
 	NV_DEBUG(dev, "ch%d\n", chan->id);
@@ -278,6 +279,8 @@ nv50_fifo_create_context(struct nouveau_channel *chan)
 			return ret;
 	}
 
+	spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
+
 	dev_priv->engine.instmem.prepare_access(dev, true);
 
 	nv_wo32(dev, ramfc, 0x08/4, chan->pushbuf_base);
@@ -306,10 +309,12 @@ nv50_fifo_create_context(struct nouveau_channel *chan)
 	ret = nv50_fifo_channel_enable(dev, chan->id, false);
 	if (ret) {
 		NV_ERROR(dev, "error enabling ch%d: %d\n", chan->id, ret);
+		spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 		nouveau_gpuobj_ref_del(dev, &chan->ramfc);
 		return ret;
 	}
 
+	spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
 	return 0;
 }