linux-kernel - Re: [PATCH] media: i2c: OV5647: ensure clock lane in LP-11 state before streaming on

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Message-ID: <20170918130837.awfb65tj66vkgmxq@valkosipuli.retiisi.org.uk>
Date:   Mon, 18 Sep 2017 16:08:37 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Jacob Chen <jacob-chen@...wrt.com>
Cc:     linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        roliveir@...opsys.com, linux-media@...r.kernel.org,
        mchehab@...nel.org, vladimir_zapolskiy@...tor.com,
        hans.verkuil@...co.com, sakari.ailus@...ux.intel.com,
        lolivei@...opsys.com, p.zabel@...gutronix.de
Subject: Re: [PATCH] media: i2c: OV5647: ensure clock lane in LP-11 state
 before streaming on

Hi Jacob,

On Mon, Sep 11, 2017 at 09:53:40AM +0800, Jacob Chen wrote:
> When I was supporting Rpi Camera Module on the ASUS Tinker board,
> I found this driver have some issues with rockchip's mipi-csi driver.
> It didn't place clock lane in LP-11 state before performing
> D-PHY initialisation.
> 
> From our experience, on some OV sensors,
> LP-11 state is not achieved while BIT(5)-0x4800 is cleared.
> 
> So let's set BIT(5) and BIT(0) both while not streaming, in order to
> coax the clock lane into LP-11 state.
> 
> 0x4800 : MIPI CTRL 00
> 	BIT(5) : clock lane gate enable
> 		0: continuous
> 		1: none-continuous
> 	BIT(0) : manually set clock lane
> 		0: Not used
> 		1: used
> 
> Changes in V2:
> 	modify commit messages

Change log doesn't belong to the commit message.

> 
> Signed-off-by: Jacob Chen <jacob-chen@...wrt.com>
> ---
>  drivers/media/i2c/ov5647.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
> index 95ce90f..247302d 100644
> --- a/drivers/media/i2c/ov5647.c
> +++ b/drivers/media/i2c/ov5647.c
> @@ -253,6 +253,10 @@ static int ov5647_stream_on(struct v4l2_subdev *sd)
>  {
>  	int ret;
>  
> +	ret = ov5647_write(sd, 0x4800, 0x04);

Could you use macros for the register bits instead of using magic number,
please, especially now that it appears that the meaning of these bits is
known?

> +	if (ret < 0)
> +		return ret;
> +
>  	ret = ov5647_write(sd, 0x4202, 0x00);
>  	if (ret < 0)
>  		return ret;
> @@ -264,6 +268,10 @@ static int ov5647_stream_off(struct v4l2_subdev *sd)
>  {
>  	int ret;
>  
> +	ret = ov5647_write(sd, 0x4800, 0x25);
> +	if (ret < 0)
> +		return ret;
> +
>  	ret = ov5647_write(sd, 0x4202, 0x0f);
>  	if (ret < 0)
>  		return ret;
> @@ -320,7 +328,10 @@ static int __sensor_init(struct v4l2_subdev *sd)
>  			return ret;
>  	}
>  
> -	return ov5647_write(sd, 0x4800, 0x04);
> +	/*
> +	 * stream off to make the clock lane into LP-11 state.
> +	 */
> +	return ov5647_stream_off(sd);
>  }
>  
>  static int ov5647_sensor_power(struct v4l2_subdev *sd, int on)
> -- 
> 2.7.4
> 

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi