[PATCH v2 3/3] usb: gadget: uvc: add configfs option for sg support

[Dan Vacura]

The scatter gather support doesn't appear to work well with some UDC hw.
Add the ability to turn on the feature depending on the controller in
use. Default the feature off since there are transmission problems with
at least one controller, dwc3.

Fixes: e81e7f9a0eb9 ("usb: gadget: uvc: add scatter gather support")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Vacura <w36195@xxxxxxxxxxxx>
---
V1 -> V2:
- no change, new patch in series

 Documentation/ABI/testing/configfs-usb-gadget-uvc | 1 +
 Documentation/usb/gadget-testing.rst              | 2 ++
 drivers/usb/gadget/function/f_uvc.c               | 2 ++
 drivers/usb/gadget/function/u_uvc.h               | 1 +
 drivers/usb/gadget/function/uvc_configfs.c        | 2 ++
 drivers/usb/gadget/function/uvc_queue.c           | 4 ++--
 6 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
index 5dfaa3f7f6a4..839a75fc28ee 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
@@ -9,6 +9,7 @@ Description:	UVC function directory
 		streaming_interval	1..16
 		function_name		string [32]
 		req_int_skip_div	unsigned int
+		sg_supported		0..1
 		===================	=============================
 
 What:		/config/usb-gadget/gadget/functions/uvc.name/control
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index f9b5a09be1f4..8e3072d6a590 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -796,6 +796,8 @@ The uvc function provides these attributes in its function directory:
 	function_name       name of the interface
 	req_int_skip_div    divisor of total requests to aid in calculating
 			    interrupt frequency, 0 indicates all interrupt
+	sg_supported        allow for scatter gather to be used if the UDC
+			    hw supports it
 	=================== ================================================
 
 There are also "control" and "streaming" subdirectories, each of which contain
diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index 75f524c83996..965cf5b48094 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -656,6 +656,7 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
 			    (opts->streaming_maxburst + 1));
 
 	uvc->video.req_int_skip_div = opts->req_int_skip_div;
+	uvc->video.queue.use_sg = opts->sg_supported;
 
 	/* Allocate endpoints. */
 	ep = usb_ep_autoconfig(cdev->gadget, &uvc_control_ep);
@@ -875,6 +876,7 @@ static struct usb_function_instance *uvc_alloc_inst(void)
 	opts->streaming_interval = 1;
 	opts->streaming_maxpacket = 1024;
 	opts->req_int_skip_div = 0;
+	opts->sg_supported = 0;
 	snprintf(opts->function_name, sizeof(opts->function_name), "UVC Camera");
 
 	ret = uvcg_attach_configfs(opts);
diff --git a/drivers/usb/gadget/function/u_uvc.h b/drivers/usb/gadget/function/u_uvc.h
index 6f73bd5638ed..5ccced629925 100644
--- a/drivers/usb/gadget/function/u_uvc.h
+++ b/drivers/usb/gadget/function/u_uvc.h
@@ -25,6 +25,7 @@ struct f_uvc_opts {
 	unsigned int					streaming_maxpacket;
 	unsigned int					streaming_maxburst;
 	unsigned int					req_int_skip_div;
+	unsigned int					sg_supported;
 
 	unsigned int					control_interface;
 	unsigned int					streaming_interface;
diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 419e926ab57e..3784c0e02d01 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -2351,6 +2351,7 @@ UVCG_OPTS_ATTR(streaming_interval, streaming_interval, 16);
 UVCG_OPTS_ATTR(streaming_maxpacket, streaming_maxpacket, 3072);
 UVCG_OPTS_ATTR(streaming_maxburst, streaming_maxburst, 15);
 UVCG_OPTS_ATTR(req_int_skip_div, req_int_skip_div, UINT_MAX);
+UVCG_OPTS_ATTR(sg_supported, sg_supported, 1);
 
 #undef UVCG_OPTS_ATTR
 
@@ -2401,6 +2402,7 @@ static struct configfs_attribute *uvc_attrs[] = {
 	&f_uvc_opts_attr_streaming_maxpacket,
 	&f_uvc_opts_attr_streaming_maxburst,
 	&f_uvc_opts_attr_req_int_skip_div,
+	&f_uvc_opts_attr_sg_supported,
 	&f_uvc_opts_string_attr_function_name,
 	NULL,
 };
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index fc65f8e73732..b11b1e4cfed6 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -149,11 +149,11 @@ int uvcg_queue_init(struct uvc_video_queue *queue, struct device *dev, enum v4l2
 	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
 	queue->queue.ops = &uvc_queue_qops;
 	queue->queue.lock = lock;
-	if (cdev->gadget->sg_supported) {
+	if (queue->use_sg && cdev->gadget->sg_supported) {
 		queue->queue.mem_ops = &vb2_dma_sg_memops;
-		queue->use_sg = 1;
 	} else {
 		queue->queue.mem_ops = &vb2_vmalloc_memops;
+		queue->use_sg = false;
 	}
 
 	queue->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY
-- 
2.34.1