Re: [PATCH v3 6/6] usb: gadget: uvc: add configfs option for sg support
From: Dan Scally
Date: Tue Oct 18 2022 - 10:09:38 EST
Hi Michael
On 18/10/2022 15:04, Michael Grzeschik wrote:
Hi Dan!
Hi Dan!
On Tue, Oct 18, 2022 at 02:27:13PM +0100, Dan Scally wrote:
Hi Dan
On 17/10/2022 21:54, Dan Vacura wrote:
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.
Signed-off-by: Dan Vacura <w36195@xxxxxxxxxxxx>
Nitpick: I would call it use_sg everywhere, but either way:
Or even only "scatter_gather". How does that sound?
Reviewed-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
Tested-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
---
V1 -> V2:
- no change, new patch in serie
V2 -> V3:
- default on, same as baseline
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 e40ca26b9c55..d08ebe3ffeb2 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->config_skip_int_div = opts->req_int_skip_div;
+ uvc->video.queue.use_sg = opts->sg_supported;
Why do you set this here?
/* 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 = 4;
+ opts->sg_supported = 1;
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 02559906a55a..3c7aa5c4bba2 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;
I am unsure, but can you actually not always use vb2_dma_sg_memops.
We have problems with this on the imx8mp EVK, because it doesn't account
for dma-range properties in device tree and so will attempt to allocate
memory outside the 4GB range that a DWC3 can access. The allocation
attempts to fall back on the swiotlb, but that's slow even if it
works...and it can fail and return -ENOMEM if the swiotlb is too small.
Probably some future work needs to fix the vb2_dma_sg_memops to take
those dma constraints into account, but for now I wouldn't force its use.
With my last patch we always set buf->mem to vb2_plane_vaddr(vb, 0);
https://lore.kernel.org/linux-usb/20221017221141.3134818-1-m.grzeschik@xxxxxxxxxxxxxx/T/#u
The condition to decide if encode_isoc_sg or encode_isoc should then
remain the last place to switch between sg or not. I would hook the
userspace decision in here.
You can also directly get to opts->scatter_gather by using
struct f_uvc_opts *opts = fi_to_f_uvc_opts(uvc->func.fi);
in the function uvcg_video_enable.
}
queue->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY
Thanks,
Michael