[PATCH 6.0 019/240] usb: gadget: uvc: limit isoc_sg to super speed gadgets

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>

commit 19905240aef0181d1e6944070eb85fce75f75bcd upstream.

The overhead of preparing sg data is high for transfers with limited
payload. When transferring isoc over high-speed usb the maximum payload
is rather small which is a good argument no to use sg. This patch is
changing the uvc_video_encode_isoc_sg encode function only to be used
for super speed gadgets.

Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221017221141.3134818-1-m.grzeschik@xxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/gadget/function/uvc_queue.c |    9 +++------
 drivers/usb/gadget/function/uvc_video.c |    9 +++++++--
 2 files changed, 10 insertions(+), 8 deletions(-)

--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -84,12 +84,9 @@ static int uvc_buffer_prepare(struct vb2
 		return -ENODEV;
 
 	buf->state = UVC_BUF_STATE_QUEUED;
-	if (queue->use_sg) {
-		buf->sgt = vb2_dma_sg_plane_desc(vb, 0);
-		buf->sg = buf->sgt->sgl;
-	} else {
-		buf->mem = vb2_plane_vaddr(vb, 0);
-	}
+	buf->sgt = vb2_dma_sg_plane_desc(vb, 0);
+	buf->sg = buf->sgt->sgl;
+	buf->mem = vb2_plane_vaddr(vb, 0);
 	buf->length = vb2_plane_size(vb, 0);
 	if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
 		buf->bytesused = 0;
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -448,6 +448,9 @@ static void uvcg_video_pump(struct work_
  */
 int uvcg_video_enable(struct uvc_video *video, int enable)
 {
+	struct uvc_device *uvc = video->uvc;
+	struct usb_composite_dev *cdev = uvc->func.config->cdev;
+	struct usb_gadget *gadget = cdev->gadget;
 	unsigned int i;
 	int ret;
 
@@ -479,9 +482,11 @@ int uvcg_video_enable(struct uvc_video *
 	if (video->max_payload_size) {
 		video->encode = uvc_video_encode_bulk;
 		video->payload_size = 0;
-	} else
-		video->encode = video->queue.use_sg ?
+	} else {
+		video->encode = (video->queue.use_sg &&
+				 !(gadget->speed <= USB_SPEED_HIGH)) ?
 			uvc_video_encode_isoc_sg : uvc_video_encode_isoc;
+	}
 
 	video->req_int_count = 0;