linux-kernel - Re: [PATCH 08/21] media: atmel: atmel-isc-base: use streaming status when queueing buffers

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Message-ID: <20211105091843.wl3le2lvo2unxfoe@uno.localdomain>
Date:   Fri, 5 Nov 2021 10:18:43 +0100
From:   Jacopo Mondi <jacopo@...ndi.org>
To:     Eugen Hristev <eugen.hristev@...rochip.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        laurent.pinchart@...asonboard.com, sakari.ailus@....fi,
        robh+dt@...nel.org, nicolas.ferre@...rochip.com
Subject: Re: [PATCH 08/21] media: atmel: atmel-isc-base: use streaming status
 when queueing buffers

Hi Eugen

On Fri, Oct 22, 2021 at 10:52:34AM +0300, Eugen Hristev wrote:
> During experiments with libcamera, it looks like vb2_is_streaming returns
> true before our start streaming is called.
> Order of operations is streamon -> queue -> start_streaming
> ISC would have started the DMA immediately when a buffer is being added
> to the vbqueue if the queue is streaming.
> It is more safe to start the DMA after the start streaming of the driver is
> called.
> Thus, even if vb2queue is streaming, add the buffer to the dma queue of the
> driver instead of actually starting the DMA process, if the start streaming
> has not been called yet.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>

I cannot really comment on the issue itself, but seeing that isc->stop
is mostly used in negated form (!isc->stop) I suggest to make it
isc->streaming ?

Thanks
   j

> ---
>  drivers/media/platform/atmel/atmel-isc-base.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
> index f3e89a892373..6f14cc549543 100644
> --- a/drivers/media/platform/atmel/atmel-isc-base.c
> +++ b/drivers/media/platform/atmel/atmel-isc-base.c
> @@ -442,12 +442,14 @@ static void isc_buffer_queue(struct vb2_buffer *vb)
>  	unsigned long flags;
>
>  	spin_lock_irqsave(&isc->dma_queue_lock, flags);
> -	if (!isc->cur_frm && list_empty(&isc->dma_queue) &&
> -		vb2_is_streaming(vb->vb2_queue)) {
> +
> +	if (!isc->cur_frm && list_empty(&isc->dma_queue) && !isc->stop) {
>  		isc->cur_frm = buf;
>  		isc_start_dma(isc);
> -	} else
> +	} else {
>  		list_add_tail(&buf->list, &isc->dma_queue);
> +	}
> +
>  	spin_unlock_irqrestore(&isc->dma_queue_lock, flags);
>  }
>
> @@ -1015,7 +1017,7 @@ static int isc_s_fmt_vid_cap(struct file *file, void *priv,
>  {
>  	struct isc_device *isc = video_drvdata(file);
>
> -	if (vb2_is_streaming(&isc->vb2_vidq))
> +	if (!isc->stop)
>  		return -EBUSY;
>
>  	return isc_set_fmt(isc, f);
> @@ -1537,7 +1539,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
>
>  		isc_update_awb_ctrls(isc);
>
> -		if (vb2_is_streaming(&isc->vb2_vidq)) {
> +		if (!isc->stop) {
>  			/*
>  			 * If we are streaming, we can update profile to
>  			 * have the new settings in place.
> @@ -1553,8 +1555,7 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
>  		}
>
>  		/* if we have autowhitebalance on, start histogram procedure */
> -		if (ctrls->awb == ISC_WB_AUTO &&
> -		    vb2_is_streaming(&isc->vb2_vidq) &&
> +		if (ctrls->awb == ISC_WB_AUTO && !isc->stop &&
>  		    ISC_IS_FORMAT_RAW(isc->config.sd_format->mbus_code))
>  			isc_set_histogram(isc, true);
>
> @@ -1830,6 +1831,8 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
>  	struct vb2_queue *q = &isc->vb2_vidq;
>  	int ret = 0;
>
> +	isc->stop = true;
> +
>  	INIT_WORK(&isc->awb_work, isc_awb_work);
>
>  	ret = v4l2_device_register_subdev_nodes(&isc->v4l2_dev);
> --
> 2.25.1
>