drm: Use USB controller's DMA mask when importing dmabufs

108 lines not on this page · raw message

index 9269092697d8..5703277c6f52 100644
@@ -32,6 +32,22 @@ static int udl_usb_resume(struct usb_interface *interface)
 	return drm_mode_config_helper_resume(dev);
 }
 
+/*
+ * FIXME: Dma-buf sharing requires DMA support by the importing device.
+ *        This function is a workaround to make USB devices work as well.
+ *        See todo.rst for how to fix the issue in the dma-buf framework.
+ */
+static struct drm_gem_object *udl_driver_gem_prime_import(struct drm_device *dev,
+							  struct dma_buf *dma_buf)
+{
+	struct udl_device *udl = to_udl(dev);
+
+	if (!udl->dmadev)
+		return ERR_PTR(-ENODEV);
+
+	return drm_gem_prime_import_dev(dev, dma_buf, udl->dmadev);
+}
+
 DEFINE_DRM_GEM_FOPS(udl_driver_fops);
 
 static const struct drm_driver driver = {

@@ -40,6 +56,7 @@ static const struct drm_driver driver = {
 	/* GEM hooks */
 	.fops = &udl_driver_fops,
 	DRM_GEM_SHMEM_DRIVER_OPS,
+	.gem_prime_import = udl_driver_gem_prime_import,
 
 	.name = DRIVER_NAME,
 	.desc = DRIVER_DESC,

index 875e73551ae9..cc16a13316e4 100644
@@ -50,6 +50,7 @@ struct urb_list {
 struct udl_device {
 	struct drm_device drm;
 	struct device *dev;
+	struct device *dmadev;
 
 	struct drm_simple_display_pipe display_pipe;
 

index 0e2a376cb075..853f147036f6 100644
@@ -315,6 +315,10 @@ int udl_init(struct udl_device *udl)
 
 	DRM_DEBUG("\n");
 
+	udl->dmadev = usb_intf_get_dma_device(to_usb_interface(dev->dev));
+	if (!udl->dmadev)
+		drm_warn(dev, "buffer sharing not supported"); /* not an error */
+
 	mutex_init(&udl->gem_lock);
 
 	if (!udl_parse_vendor_descriptor(udl)) {

@@ -343,12 +347,18 @@ int udl_init(struct udl_device *udl)
 err:
 	if (udl->urbs.count)
 		udl_free_urb_list(dev);
+	put_device(udl->dmadev);
 	DRM_ERROR("%d\n", ret);
 	return ret;
 }
 
 int udl_drop_usb(struct drm_device *dev)
 {
+	struct udl_device *udl = to_udl(dev);
+
 	udl_free_urb_list(dev);
+	put_device(udl->dmadev);
+	udl->dmadev = NULL;
+
 	return 0;
 }

index 8f07b0516100..a566bb494e24 100644
@@ -748,6 +748,38 @@ void usb_put_intf(struct usb_interface *intf)
 }
 EXPORT_SYMBOL_GPL(usb_put_intf);
 
+/**
+ * usb_intf_get_dma_device - acquire a reference on the usb interface's DMA endpoint
+ * @intf: the usb interface
+ *
+ * While a USB device cannot perform DMA operations by itself, many USB
+ * controllers can. A call to usb_intf_get_dma_device() returns the DMA endpoint
+ * for the given USB interface, if any. The returned device structure must be
+ * released with put_device().
+ *
+ * See also usb_get_dma_device().
+ *
+ * Returns: A reference to the usb interface's DMA endpoint; or NULL if none
+ *          exists.
+ */
+struct device *usb_intf_get_dma_device(struct usb_interface *intf)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct device *dmadev;
+
+	if (!udev->bus)
+		return NULL;
+
+	dmadev = get_device(udev->bus->sysdev);
+	if (!dmadev || !dmadev->dma_mask) {
+		put_device(dmadev);
+		return NULL;
+	}
+
+	return dmadev;
+}
+EXPORT_SYMBOL_GPL(usb_intf_get_dma_device);
+
 /*			USB device locking
  *
  * USB devices and interfaces are locked using the semaphore in their

index 7d72c4e0713c..d6a41841b93e 100644
@@ -746,6 +746,8 @@ extern int usb_lock_device_for_reset(struct usb_device *udev,
 extern int usb_reset_device(struct usb_device *dev);
 extern void usb_queue_reset_device(struct usb_interface *dev);
 
+extern struct device *usb_intf_get_dma_device(struct usb_interface *intf);
+
 #ifdef CONFIG_ACPI
 extern int usb_acpi_set_power_state(struct usb_device *hdev, int index,
 	bool enable);