@@ -560,6 +560,27 @@ Some of these date from the very introdu
Level: Intermediate
+Remove automatic page mapping from dma-buf importing
+----------------------------------------------------
+
+When importing dma-bufs, the dma-buf and PRIME frameworks automatically map
+imported pages into the importer's DMA area. drm_gem_prime_fd_to_handle() and
+drm_gem_prime_handle_to_fd() require that importers call dma_buf_attach()
+even if they never do actual device DMA, but only CPU access through
+dma_buf_vmap(). This is a problem for USB devices, which do not support DMA
+operations.
+
+To fix the issue, automatic page mappings should be removed from the
+buffer-sharing code. Fixing this is a bit more involved, since the import/export
+cache is also tied to &drm_gem_object.import_attach. Meanwhile we paper over
+this problem for USB devices by fishing out the USB host controller device, as
+long as that supports DMA. Otherwise importing can still needlessly fail.
+
+Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter
+
+Level: Advanced
+
+
Better Testing
==============
@@ -83,6 +83,7 @@ MODULE_PARM_DESC(eco_mode, "Turn on Eco
struct gm12u320_device {
struct drm_device dev;
+ struct device *dmadev;
struct drm_simple_display_pipe pipe;
struct drm_connector conn;
struct usb_device *udev;
@@ -598,6 +599,22 @@ static const uint64_t gm12u320_pipe_modi
DRM_FORMAT_MOD_INVALID
};
+/*
+ * 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 *gm12u320_gem_prime_import(struct drm_device *dev,
+ struct dma_buf *dma_buf)
+{
+ struct gm12u320_device *gm12u320 = to_gm12u320(dev);
+
+ if (!gm12u320->dmadev)
+ return ERR_PTR(-ENODEV);
+
+ return drm_gem_prime_import_dev(dev, dma_buf, gm12u320->dmadev);
+}
+
DEFINE_DRM_GEM_FOPS(gm12u320_fops);
static struct drm_driver gm12u320_drm_driver = {
@@ -611,6 +628,7 @@ static struct drm_driver gm12u320_drm_dr
.fops = &gm12u320_fops,
DRM_GEM_SHMEM_DRIVER_OPS,
+ .gem_prime_import = gm12u320_gem_prime_import,
};
static const struct drm_mode_config_funcs gm12u320_mode_config_funcs = {
@@ -637,16 +655,19 @@ static int gm12u320_usb_probe(struct usb
struct gm12u320_device, dev);
if (IS_ERR(gm12u320))
return PTR_ERR(gm12u320);
+ dev = &gm12u320->dev;
+
+ gm12u320->dmadev = usb_intf_get_dma_device(to_usb_interface(dev->dev));
+ if (!gm12u320->dmadev)
+ drm_warn(dev, "buffer sharing not supported"); /* not an error */
gm12u320->udev = interface_to_usbdev(interface);
INIT_DELAYED_WORK(&gm12u320->fb_update.work, gm12u320_fb_update_work);
mutex_init(&gm12u320->fb_update.lock);
- dev = &gm12u320->dev;
-
ret = drmm_mode_config_init(dev);
if (ret)
- return ret;
+ goto err_put_device;
dev->mode_config.min_width = GM12U320_USER_WIDTH;
dev->mode_config.max_width = GM12U320_USER_WIDTH;
@@ -656,15 +677,15 @@ static int gm12u320_usb_probe(struct usb
ret = gm12u320_usb_alloc(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = gm12u320_set_ecomode(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = gm12u320_conn_init(gm12u320);
if (ret)
- return ret;
+ goto err_put_device;
ret = drm_simple_display_pipe_init(&gm12u320->dev,
&gm12u320->pipe,
@@ -674,24 +695,31 @@ static int gm12u320_usb_probe(struct usb
gm12u320_pipe_modifiers,
&gm12u320->conn);
if (ret)
- return ret;
+ goto err_put_device;
drm_mode_config_reset(dev);
usb_set_intfdata(interface, dev);
ret = drm_dev_register(dev, 0);
if (ret)
- return ret;
+ goto err_put_device;
drm_fbdev_generic_setup(dev, 0);
return 0;
+
+err_put_device:
+ put_device(gm12u320->dmadev);
+ return ret;
}
static void gm12u320_usb_disconnect(struct usb_interface *interface)
{
struct drm_device *dev = usb_get_intfdata(interface);
+ struct gm12u320_device *gm12u320 = to_gm12u320(dev);
+ put_device(gm12u320->dmadev);
+ gm12u320->dmadev = NULL;
drm_dev_unplug(dev);
drm_atomic_helper_shutdown(dev);
}
@@ -32,6 +32,22 @@ static int udl_usb_resume(struct usb_int
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 struct drm_driver driver = {
@@ -42,6 +58,7 @@ static struct drm_driver driver = {
.fops = &udl_driver_fops,
DRM_GEM_SHMEM_DRIVER_OPS,
+ .gem_prime_import = udl_driver_gem_prime_import,
.name = DRIVER_NAME,
.desc = DRIVER_DESC,
@@ -50,6 +50,7 @@ struct urb_list {
struct udl_device {
struct drm_device drm;
struct device *dev;
+ struct device *dmadev;
struct usb_device *udev;
struct drm_simple_display_pipe display_pipe;
@@ -314,6 +314,10 @@ 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(dev, udl->udev)) {
@@ -342,12 +346,18 @@ 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;
}
@@ -748,6 +748,38 @@ void usb_put_intf(struct usb_interface *
}
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
@@ -746,6 +746,8 @@ extern int usb_lock_device_for_reset(str
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);