Re: [PATCH v1 3/3] media: uvcvideo: Do power management granularly

From: Laurent Pinchart
Date: Tue Oct 25 2022 - 08:48:33 EST

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Hi Ricardo,

Thank you for the patch.

On Tue, Sep 20, 2022 at 04:09:52PM +0200, Ricardo Ribalda wrote:
> Instead of suspending/resume the USB device at open()/close(), do it
> when the device is actually used.
>
> This way we can reduce the power consumption when a service is holding
> the video device and leaving it in an idle state.
>
> Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 8d5002543e2c..b9642afabd9b 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -25,6 +25,46 @@
>
> #include "uvcvideo.h"
>
> +/* ------------------------------------------------------------------------
> + * UVC power management
> + */
> +
> +static int uvc_pm_get(struct uvc_streaming *stream)
> +{
> + int ret = 0;

No need to initialize ret to 0.

> +
> + ret = usb_autopm_get_interface(stream->dev->intf);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&stream->dev->lock);
> + if (!stream->dev->users)
> + ret = uvc_status_start(stream->dev, GFP_KERNEL);

For devices that don't have a status endpoint, we will end up calling
uvc_status_start() and uvc_status_stop() around most ioctl calls (all
call sites of uvc_pm_get() and uvc_pm_put() below). uvc_status_start()
and uvc_status_stop() are no-op in that case, but conceptually I don't
think that's very nice. Could we instead keep the status start/stop
calls to open()/release() ?

If you don't mind, I'll give this a try and post a new version of the
patch, that should be faster than going through another review round.

> + if (!ret)
> + stream->dev->users++;
> + mutex_unlock(&stream->dev->lock);
> +
> + if (ret)
> + usb_autopm_put_interface(stream->dev->intf);
> +
> + return ret;
> +}
> +
> +static void uvc_pm_put(struct uvc_streaming *stream)
> +{
> + mutex_lock(&stream->dev->lock);
> + if (WARN_ON(!stream->dev->users)) {
> + mutex_unlock(&stream->dev->lock);
> + return;
> + }
> + stream->dev->users--;
> + if (!stream->dev->users)
> + uvc_status_stop(stream->dev);
> + mutex_unlock(&stream->dev->lock);
> +
> + usb_autopm_put_interface(stream->dev->intf);
> +}
> +
> /* ------------------------------------------------------------------------
> * UVC ioctls
> */
> @@ -249,6 +289,9 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
> * developers test their webcams with the Linux driver as well as with
> * the Windows driver).
> */
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> mutex_lock(&stream->mutex);
> if (stream->dev->quirks & UVC_QUIRK_PROBE_EXTRAFIELDS)
> probe->dwMaxVideoFrameSize =
> @@ -257,6 +300,7 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
> /* Probe the device. */
> ret = uvc_probe_video(stream, probe);
> mutex_unlock(&stream->mutex);
> + uvc_pm_put(stream);
> if (ret < 0)
> return ret;
>
> @@ -468,7 +512,13 @@ static int uvc_v4l2_set_streamparm(struct uvc_streaming *stream,
> }
>
> /* Probe the device with the new settings. */
> + ret = uvc_pm_get(stream);
> + if (ret) {
> + mutex_unlock(&stream->mutex);
> + return ret;
> + }
> ret = uvc_probe_video(stream, &probe);
> + uvc_pm_put(stream);
> if (ret < 0) {
> mutex_unlock(&stream->mutex);
> return ret;
> @@ -559,36 +609,29 @@ static int uvc_v4l2_open(struct file *file)
> {
> struct uvc_streaming *stream;
> struct uvc_fh *handle;
> - int ret = 0;
>
> stream = video_drvdata(file);
> uvc_dbg(stream->dev, CALLS, "%s\n", __func__);
>
> - ret = usb_autopm_get_interface(stream->dev->intf);
> - if (ret < 0)
> - return ret;
> -
> /* Create the device handle. */
> handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> - if (handle == NULL) {
> - usb_autopm_put_interface(stream->dev->intf);
> + if (!handle)
> return -ENOMEM;
> - }
>
> - mutex_lock(&stream->dev->lock);
> - if (stream->dev->users == 0) {
> - ret = uvc_status_start(stream->dev, GFP_KERNEL);
> - if (ret < 0) {
> - mutex_unlock(&stream->dev->lock);
> - usb_autopm_put_interface(stream->dev->intf);
> + /*
> + * If the uvc evdev exists we cannot suspend when the device
> + * is idle. Otherwise we will miss button actions.
> + */
> + if (stream->dev->input) {
> + int ret;
> +
> + ret = uvc_pm_get(stream);
> + if (ret) {
> kfree(handle);
> return ret;
> }
> }
>
> - stream->dev->users++;
> - mutex_unlock(&stream->dev->lock);
> -
> v4l2_fh_init(&handle->vfh, &stream->vdev);
> v4l2_fh_add(&handle->vfh);
> handle->chain = stream->chain;
> @@ -610,6 +653,12 @@ static int uvc_v4l2_release(struct file *file)
> if (uvc_has_privileges(handle))
> uvc_queue_release(&stream->queue);
>
> + if (handle->is_streaming)
> + uvc_pm_put(stream);
> +
> + if (stream->dev->input)
> + uvc_pm_put(stream);
> +
> /* Release the file handle. */
> uvc_dismiss_privileges(handle);
> v4l2_fh_del(&handle->vfh);
> @@ -617,12 +666,6 @@ static int uvc_v4l2_release(struct file *file)
> kfree(handle);
> file->private_data = NULL;
>
> - mutex_lock(&stream->dev->lock);
> - if (--stream->dev->users == 0)
> - uvc_status_stop(stream->dev);
> - mutex_unlock(&stream->dev->lock);
> -
> - usb_autopm_put_interface(stream->dev->intf);
> return 0;
> }
>
> @@ -849,9 +892,17 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
>
> if (handle->is_streaming)
> goto unlock;
> +
> + ret = uvc_pm_get(stream);
> + if (ret)
> + goto unlock;
> +
> ret = uvc_queue_streamon(&stream->queue, type);
> handle->is_streaming = !ret;
>
> + if (!handle->is_streaming)
> + uvc_pm_put(stream);
> +
> unlock:
> mutex_unlock(&stream->mutex);
>
> @@ -875,6 +926,9 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
> ret = uvc_queue_streamoff(&stream->queue, type);
> handle->is_streaming = !!ret;
>
> + if (!handle->is_streaming)
> + uvc_pm_put(stream);
> +
> unlock:
> mutex_unlock(&stream->mutex);
>
> @@ -928,6 +982,7 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> u8 *buf;
> int ret;
>
> @@ -941,9 +996,16 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
> if (!buf)
> return -ENOMEM;
>
> + ret = uvc_pm_get(stream);
> + if (ret) {
> + kfree(buf);
> + return ret;
> + }
> +
> ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id,
> chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
> buf, 1);
> + uvc_pm_put(stream);
> if (!ret)
> *input = *buf - 1;
>
> @@ -956,6 +1018,7 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> u8 *buf;
> int ret;
>
> @@ -977,10 +1040,17 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
> if (!buf)
> return -ENOMEM;
>
> + ret = uvc_pm_get(stream);
> + if (ret) {
> + kfree(buf);
> + return ret;
> + }
> +
> *buf = input + 1;
> ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
> chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
> buf, 1);
> + uvc_pm_put(stream);
> kfree(buf);
>
> return ret;
> @@ -991,8 +1061,15 @@ static int uvc_ioctl_queryctrl(struct file *file, void *fh,
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> + int ret;
>
> - return uvc_query_v4l2_ctrl(chain, qc);
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> + ret = uvc_query_v4l2_ctrl(chain, qc);
> + uvc_pm_put(stream);
> + return ret;
> }
>
> static int uvc_ioctl_query_ext_ctrl(struct file *file, void *fh,
> @@ -1000,10 +1077,15 @@ static int uvc_ioctl_query_ext_ctrl(struct file *file, void *fh,
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> struct v4l2_queryctrl qc = { qec->id };
> int ret;
>
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> ret = uvc_query_v4l2_ctrl(chain, &qc);
> + uvc_pm_put(stream);
> if (ret)
> return ret;
>
> @@ -1049,6 +1131,7 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> struct v4l2_ext_control *ctrl = ctrls->controls;
> unsigned int i;
> int ret;
> @@ -1073,22 +1156,30 @@ static int uvc_ioctl_g_ext_ctrls(struct file *file, void *fh,
> return 0;
> }
>
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> ret = uvc_ctrl_begin(chain);
> - if (ret < 0)
> + if (ret < 0) {
> + uvc_pm_put(stream);
> return ret;
> + }
>
> for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> ret = uvc_ctrl_get(chain, ctrl);
> if (ret < 0) {
> uvc_ctrl_rollback(handle);
> ctrls->error_idx = i;
> - return ret;
> + goto done;
> }
> }
>
> ctrls->error_idx = 0;
>
> - return uvc_ctrl_rollback(handle);
> + ret = uvc_ctrl_rollback(handle);
> +done:
> + uvc_pm_put(stream);
> + return ret;
> }
>
> static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> @@ -1097,6 +1188,7 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> {
> struct v4l2_ext_control *ctrl = ctrls->controls;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> unsigned int i;
> int ret;
>
> @@ -1104,9 +1196,15 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> if (ret < 0)
> return ret;
>
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> +
> ret = uvc_ctrl_begin(chain);
> - if (ret < 0)
> + if (ret < 0) {
> + uvc_pm_put(stream);
> return ret;
> + }
>
> for (i = 0; i < ctrls->count; ++ctrl, ++i) {
> ret = uvc_ctrl_set(handle, ctrl);
> @@ -1114,16 +1212,20 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
> uvc_ctrl_rollback(handle);
> ctrls->error_idx = ioctl == VIDIOC_S_EXT_CTRLS ?
> ctrls->count : i;
> - return ret;
> + goto done;
> }
> }
>
> ctrls->error_idx = 0;
>
> if (ioctl == VIDIOC_S_EXT_CTRLS)
> - return uvc_ctrl_commit(handle, ctrls);
> + ret = uvc_ctrl_commit(handle, ctrls);
> else
> - return uvc_ctrl_rollback(handle);
> + ret = uvc_ctrl_rollback(handle);
> +
> +done:
> + uvc_pm_put(stream);
> + return ret;
> }
>
> static int uvc_ioctl_s_ext_ctrls(struct file *file, void *fh,
> @@ -1147,8 +1249,16 @@ static int uvc_ioctl_querymenu(struct file *file, void *fh,
> {
> struct uvc_fh *handle = fh;
> struct uvc_video_chain *chain = handle->chain;
> + struct uvc_streaming *stream = handle->stream;
> + int ret;
> +
> + ret = uvc_pm_get(stream);
> + if (ret)
> + return ret;
> + ret = uvc_query_v4l2_menu(chain, qm);
> + uvc_pm_put(stream);
>
> - return uvc_query_v4l2_menu(chain, qm);
> + return ret;
> }
>
> static int uvc_ioctl_g_selection(struct file *file, void *fh,
>

--
Regards,

Laurent Pinchart

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