Hi Eugen,
On 10/03/2022 10:51, Eugen Hristev wrote:
> The AWB workqueue runs in a kernel thread and needs to be synchronized
> w.r.t. the streaming status.
> It is possible that streaming is stopped while the AWB workq is running.
> In this case it is likely that the check for vb2_start_streaming_called is done
> at one point in time, but the AWB computations are done later, including a call
> to isc_update_profile, which requires streaming to be started.
> Thus , isc_update_profile will fail if during this operation sequence the
> streaming was stopped.
> To solve this issue, a mutex is added, that will serialize the awb work and
> streaming stopping, with the mention that either streaming is stopped
> completely including termination of the last frame is done, and after that
> the AWB work can check stream status and stop; either first AWB work is
> completed and after that the streaming can stop correctly.
> The awb spin lock cannot be used since this spinlock is taken in the same
> context and using it in the stop streaming will result in a recursion BUG.
Please keep the line length in a commit log to no more than 75.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx>
> Reviewed-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> ---
> drivers/media/platform/atmel/atmel-isc-base.c | 29 ++++++++++++++++---
> drivers/media/platform/atmel/atmel-isc.h | 2 ++
> 2 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
<snip>
> @@ -1548,6 +1564,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
> */
> v4l2_ctrl_activate(isc->do_wb_ctrl, false);
> }
> + mutex_unlock(&isc->awb_mutex);
Huh? What is this unlock doing here? Am I missing something?
Regards,
Hans
>
> /* if we have autowhitebalance on, start histogram procedure */
> if (ctrls->awb == ISC_WB_AUTO &&
> @@ -1740,6 +1757,7 @@ static void isc_async_unbind(struct v4l2_async_notifier *notifier,
> {
> struct isc_device *isc = container_of(notifier->v4l2_dev,
> struct isc_device, v4l2_dev);
> + mutex_destroy(&isc->awb_mutex);
> cancel_work_sync(&isc->awb_work);
> video_unregister_device(&isc->video_dev);
> v4l2_ctrl_handler_free(&isc->ctrls.handler);
> @@ -1850,6 +1868,8 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
> isc->current_subdev = container_of(notifier,
> struct isc_subdev_entity, notifier);
> mutex_init(&isc->lock);
> + mutex_init(&isc->awb_mutex);
> +
> init_completion(&isc->comp);
>
> /* Initialize videobuf2 queue */
> @@ -1930,6 +1950,7 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
> video_unregister_device(vdev);
>
> isc_async_complete_err:
> + mutex_destroy(&isc->awb_mutex);
> mutex_destroy(&isc->lock);
> return ret;
> }
> diff --git a/drivers/media/platform/atmel/atmel-isc.h b/drivers/media/platform/atmel/atmel-isc.h
> index 9cc69c3ae26d..f98f25a55e73 100644
> --- a/drivers/media/platform/atmel/atmel-isc.h
> +++ b/drivers/media/platform/atmel/atmel-isc.h
> @@ -229,6 +229,7 @@ enum isc_scaler_pads {
> *
> * @lock: lock for serializing userspace file operations
> * with ISC operations
> + * @awb_mutex: serialize access to streaming status from awb work queue
> * @awb_lock: lock for serializing awb work queue operations
> * with DMA/buffer operations
> *
> @@ -307,6 +308,7 @@ struct isc_device {
> struct work_struct awb_work;
>
> struct mutex lock;
> + struct mutex awb_mutex;
> spinlock_t awb_lock;
>
> struct regmap_field *pipeline[ISC_PIPE_LINE_NODE_NUM];
