From mboxrd@z Thu Jan  1 00:00:00 1970
From: laurent.pinchart@ideasonboard.com (Laurent Pinchart)
Date: Thu, 05 Mar 2015 12:39:42 +0200
Subject: [PATCH 1/3] media: atmel-isi: move the peripheral clock to
 start/stop_stream() function
In-Reply-To: <1425531661-20040-2-git-send-email-josh.wu@atmel.com>
References: <1425531661-20040-1-git-send-email-josh.wu@atmel.com>
 <1425531661-20040-2-git-send-email-josh.wu@atmel.com>
Message-ID: <16387779.aQaQKCyNOp@avalon>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi Josh,

Thank you for the patch.

On Thursday 05 March 2015 13:00:59 Josh Wu wrote:
> As the clock_start/stop() use to control the mclk for the sensor not the
> ISI peripheral clock.
> So we move them to start/stop_stream() function.

Then the driver will access registers with the peripheral clock disabled, for 
instance in isi_camera_set_fmt() (calling configure_geometry), 
isi_camera_set_bus_param() or atmel_isi_probe(). Isn't that a problem ? Or are 
all registers guaranteed to be accessible (and retained) when the clock is 
disabled ?

> Signed-off-by: Josh Wu <josh.wu@atmel.com>
> ---
> 
>  drivers/media/platform/soc_camera/atmel-isi.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/soc_camera/atmel-isi.c
> b/drivers/media/platform/soc_camera/atmel-isi.c index 1208818..eb179e7
> 100644
> --- a/drivers/media/platform/soc_camera/atmel-isi.c
> +++ b/drivers/media/platform/soc_camera/atmel-isi.c
> @@ -386,6 +386,10 @@ static int start_streaming(struct vb2_queue *vq,
> unsigned int count) struct atmel_isi *isi = ici->priv;
>  	int ret;
> 
> +	ret = clk_prepare_enable(isi->pclk);
> +	if (ret)
> +		return ret;
> +
>  	/* Reset ISI */
>  	ret = atmel_isi_wait_status(isi, WAIT_ISI_RESET);
>  	if (ret < 0) {
> @@ -445,6 +449,8 @@ static void stop_streaming(struct vb2_queue *vq)
>  	ret = atmel_isi_wait_status(isi, WAIT_ISI_DISABLE);
>  	if (ret < 0)
>  		dev_err(icd->parent, "Disable ISI timed out\n");
> +
> +	clk_disable_unprepare(isi->pclk);
>  }
> 
>  static struct vb2_ops isi_video_qops = {
> @@ -723,14 +729,9 @@ static int isi_camera_clock_start(struct
> soc_camera_host *ici) struct atmel_isi *isi = ici->priv;
>  	int ret;
> 
> -	ret = clk_prepare_enable(isi->pclk);
> -	if (ret)
> -		return ret;
> -
>  	if (!IS_ERR(isi->mck)) {
>  		ret = clk_prepare_enable(isi->mck);
>  		if (ret) {
> -			clk_disable_unprepare(isi->pclk);
>  			return ret;
>  		}
>  	}
> @@ -745,7 +746,6 @@ static void isi_camera_clock_stop(struct soc_camera_host
> *ici)
> 
>  	if (!IS_ERR(isi->mck))
>  		clk_disable_unprepare(isi->mck);
> -	clk_disable_unprepare(isi->pclk);
>  }
> 
>  static unsigned int isi_camera_poll(struct file *file, poll_table *pt)

-- 
Regards,

Laurent Pinchart