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authorThomas Zimmermann <tzimmermann@suse.de>2021-03-03 16:32:29 +0300
committerMaarten Lankhorst <maarten.lankhorst@linux.intel.com>2021-03-11 13:11:33 +0300
commit659ab7a49cbebe0deffcbe1f9560e82006b21817 (patch)
tree6a74286e56b6257f68e6bbee23389469acd25408 /drivers/usb
parent301469c121bfe4a243460ed0b6abf391139c6bb1 (diff)
downloadlinux-659ab7a49cbebe0deffcbe1f9560e82006b21817.tar.xz
drm: Use USB controller's DMA mask when importing dmabufs
USB devices cannot perform DMA and hence have no dma_mask set in their device structure. Therefore importing dmabuf into a USB-based driver fails, which breaks joining and mirroring of display in X11. For USB devices, pick the associated USB controller as attachment device. This allows the DRM import helpers to perform the DMA setup. If the DMA controller does not support DMA transfers, we're out of luck and cannot import. Our current USB-based DRM drivers don't use DMA, so the actual DMA device is not important. Tested by joining/mirroring displays of udl and radeon under Gnome/X11. v8: * release dmadev if device initialization fails (Noralf) * fix commit description (Noralf) v7: * fix use-before-init bug in gm12u320 (Dan) v6: * implement workaround in DRM drivers and hold reference to DMA device while USB device is in use * remove dev_is_usb() (Greg) * collapse USB helper into usb_intf_get_dma_device() (Alan) * integrate Daniel's TODO statement (Daniel) * fix typos (Greg) v5: * provide a helper for USB interfaces (Alan) * add FIXME item to documentation and TODO list (Daniel) v4: * implement workaround with USB helper functions (Greg) * use struct usb_device->bus->sysdev as DMA device (Takashi) v3: * drop gem_create_object * use DMA mask of USB controller, if any (Daniel, Christian, Noralf) v2: * move fix to importer side (Christian, Daniel) * update SHMEM and CMA helpers for new PRIME callbacks Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Fixes: 6eb0233ec2d0 ("usb: don't inherity DMA properties for USB devices") Tested-by: Pavel Machek <pavel@ucw.cz> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Christian König <christian.koenig@amd.com> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Noralf Trønnes <noralf@tronnes.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <stable@vger.kernel.org> # v5.10+ Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Link: https://patchwork.freedesktop.org/patch/msgid/20210303133229.3288-1-tzimmermann@suse.de Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/core/usb.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 8f07b0516100..a566bb494e24 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -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