Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220920-resend-powersave-v1-0-123aa2ba3836@chromium.org>
 <20220920-resend-powersave-v1-3-123aa2ba3836@chromium.org> <Y1facEGMo+N1v0RU@pendragon.ideasonboard.com>
In-Reply-To: <Y1facEGMo+N1v0RU@pendragon.ideasonboard.com>
From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Tue, 25 Oct 2022 14:55:17 +0200
Message-ID: <CANiDSCv3WPH+BYgWEONQK2AsVgEdSvXE6_5JSXRrYVa0j=cBNg@mail.gmail.com>
Subject: Re: [PATCH v1 3/3] media: uvcvideo: Do power management granularly
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-kernel@vger.kernel.org, Tomasz Figa <tfiga@chromium.org>,
        linux-media@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Laurent

Thanks for the review!

On Tue, 25 Oct 2022 at 14:46, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> 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@chromium.org>
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> >
> > 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() ?


I do not think that we can call uvc_status_start without calling
usb_autopm_get_interface()

We could add a flag on the device, and do something like:

if (!stream->dev->users && stream->dev->has_ststatus_enpoint)
            ret = uvc_status_start(stream->dev, GFP_KERNEL);

But I am not sure what is cleaner...


>
> 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


--
Ricardo Ribalda