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From:   Ricardo Ribalda <ribalda@chromium.org>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Ricardo Ribalda <ribalda@chromium.org>
Subject: [PATCH v2] media: uvcvideo: Do power management granularly
Date:   Mon, 24 Jan 2022 17:00:16 +0100
Message-Id: <20220124160016.192081-1-ribalda@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---

v2: Kudos to Laurent!

We cannot suspend if we can read events from the video device.

 drivers/media/usb/uvc/uvc_v4l2.c | 202 +++++++++++++++++++++++++------
 drivers/media/usb/uvc/uvcvideo.h |   1 +
 2 files changed, 169 insertions(+), 34 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 711556d13d03..f557ba0daa46 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -25,6 +25,55 @@
 
 #include "uvcvideo.h"
 
+/* ------------------------------------------------------------------------
+ * UVC power management
+ */
+
+static int uvc_pm_get(struct uvc_streaming *stream)
+{
+	int ret = 0;
+
+	if (!video_is_registered(&stream->vdev))
+		return -ENODEV;
+
+	/*
+	 * We cannot hold dev->lock when calling autopm_get_interface.
+	 */
+	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);
+	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)
+{
+	if (!video_is_registered(&stream->vdev))
+		return;
+
+	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
  */
@@ -251,8 +300,14 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream,
 			stream->ctrl.dwMaxVideoFrameSize;
 
 	/* Probe the device. */
+	ret = uvc_pm_get(stream);
+	if (ret) {
+		mutex_unlock(&stream->mutex);
+		goto done;
+	}
 	ret = uvc_probe_video(stream, probe);
 	mutex_unlock(&stream->mutex);
+	uvc_pm_put(stream);
 	if (ret < 0)
 		goto done;
 
@@ -464,7 +519,13 @@ 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;
@@ -555,35 +616,25 @@ 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);
-			kfree(handle);
-			return ret;
-		}
+	/*
+	 * If the uvc evdev exists we cannot suspend when the device
+	 * is idle. Otherwise we will miss button actions.
+	 */
+#ifdef CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV
+	if (uvc_pm_get(stream)) {
+		kfree(handle);
+		return -ENODEV;
 	}
-
-	stream->dev->users++;
-	mutex_unlock(&stream->dev->lock);
+#endif
 
 	v4l2_fh_init(&handle->vfh, &stream->vdev);
 	v4l2_fh_add(&handle->vfh);
@@ -606,6 +657,13 @@ 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);
+
+#ifdef CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV
+	uvc_pm_put(stream);
+#endif
+
 	/* Release the file handle. */
 	uvc_dismiss_privileges(handle);
 	v4l2_fh_del(&handle->vfh);
@@ -613,12 +671,6 @@ 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;
 }
 
@@ -842,7 +894,21 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
 		return -EBUSY;
 
 	mutex_lock(&stream->mutex);
+	if (!handle->is_streaming) {
+		ret = uvc_pm_get(stream);
+		if (ret)
+			goto unlock;
+	}
+
 	ret = uvc_queue_streamon(&stream->queue, type);
+
+	if (ret && !handle->is_streaming)
+		uvc_pm_put(stream);
+
+	if (!ret)
+		handle->is_streaming = true;
+
+unlock:
 	mutex_unlock(&stream->mutex);
 
 	return ret;
@@ -859,6 +925,10 @@ static int uvc_ioctl_streamoff(struct file *file, void *fh,
 
 	mutex_lock(&stream->mutex);
 	uvc_queue_streamoff(&stream->queue, type);
+	if (handle->is_streaming) {
+		handle->is_streaming = false;
+		uvc_pm_put(stream);
+	}
 	mutex_unlock(&stream->mutex);
 
 	return 0;
@@ -909,6 +979,7 @@ 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;
 
@@ -922,9 +993,16 @@ 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;
 
@@ -937,6 +1015,7 @@ 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;
 
@@ -958,10 +1037,17 @@ 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;
@@ -972,8 +1058,15 @@ 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,
@@ -981,10 +1074,15 @@ 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;
 
@@ -1030,6 +1128,7 @@ 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;
@@ -1054,22 +1153,30 @@ 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;
+			uvc_pm_put(stream);
 			return ret;
 		}
 	}
 
 	ctrls->error_idx = 0;
 
-	return uvc_ctrl_rollback(handle);
+	ret = uvc_ctrl_rollback(handle);
+	uvc_pm_put(stream);
+	return ret;
 }
 
 static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
@@ -1078,6 +1185,7 @@ 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;
 
@@ -1085,9 +1193,15 @@ 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);
@@ -1095,6 +1209,7 @@ 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;
+			uvc_pm_put(stream);
 			return ret;
 		}
 	}
@@ -1102,9 +1217,12 @@ static int uvc_ioctl_s_try_ext_ctrls(struct uvc_fh *handle,
 	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);
+
+	uvc_pm_put(stream);
+	return ret;
 }
 
 static int uvc_ioctl_s_ext_ctrls(struct file *file, void *fh,
@@ -1119,8 +1237,16 @@ static int uvc_ioctl_try_ext_ctrls(struct file *file, void *fh,
 				   struct v4l2_ext_controls *ctrls)
 {
 	struct uvc_fh *handle = fh;
+	struct uvc_streaming *stream = handle->stream;
+	int ret;
+
+	ret = uvc_pm_get(stream);
+	if (ret)
+		return ret;
+	ret = uvc_ioctl_s_try_ext_ctrls(handle, ctrls, VIDIOC_TRY_EXT_CTRLS);
+	uvc_pm_put(stream);
 
-	return uvc_ioctl_s_try_ext_ctrls(handle, ctrls, VIDIOC_TRY_EXT_CTRLS);
+	return ret;
 }
 
 static int uvc_ioctl_querymenu(struct file *file, void *fh,
@@ -1128,8 +1254,16 @@ 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;
 
-	return uvc_query_v4l2_menu(chain, qm);
+	ret = uvc_pm_get(stream);
+	if (ret)
+		return ret;
+	ret = uvc_query_v4l2_menu(chain, qm);
+	uvc_pm_put(stream);
+
+	return ret;
 }
 
 static int uvc_ioctl_g_selection(struct file *file, void *fh,
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 143230b3275b..5958b2a54dab 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -720,6 +720,7 @@ enum uvc_handle_state {
 
 struct uvc_fh {
 	struct v4l2_fh vfh;
+	bool is_streaming;
 	struct uvc_video_chain *chain;
 	struct uvc_streaming *stream;
 	enum uvc_handle_state state;
-- 
2.35.0.rc0.227.g00780c9af4-goog