linux-kernel - Re: [PATCH v3 11/19] media: i2c: rdacm21: Add dealy after OV490 reset

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Message-ID: <99971a13-4d02-2255-6653-569915da181d@ideasonboard.com>
Date:   Fri, 19 Mar 2021 16:49:44 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        laurent.pinchart+renesas@...asonboard.com,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 11/19] media: i2c: rdacm21: Add dealy after OV490 reset

Hi Jacopo,

s/dealy/delay/ in $SUBJECT

On 19/03/2021 16:41, Jacopo Mondi wrote:
> Add a delay after the OV490 chip is put in reset state. The reset
> signal shall be held for at least 250 useconds.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
>  drivers/media/i2c/rdacm21.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> index babd14b21252..875bec9f7904 100644
> --- a/drivers/media/i2c/rdacm21.c
> +++ b/drivers/media/i2c/rdacm21.c
> @@ -448,7 +448,10 @@ static int rdacm21_init(struct v4l2_subdev *sd, unsigned int val)
>  	if (ret)
>  		return ret;
>  
> -	/* Enable GPIO1 and hold OV490 in reset during max9271 configuration. */
> +	/*
> +	 * Enable GPIO1 and hold OV490 in reset during max9271 configuration.
> +	 * The reset signal has to be asserted for at least 250 useconds.
> +	 */
>  	ret = max9271_enable_gpios(&dev->serializer, MAX9271_GPIO1OUT);
>  	if (ret)
>  		return ret;
> @@ -456,6 +459,7 @@ static int rdacm21_init(struct v4l2_subdev *sd, unsigned int val)
>  	ret = max9271_clear_gpios(&dev->serializer, MAX9271_GPIO1OUT);
>  	if (ret)
>  		return ret;
> +	usleep_range(250, 500);

Aha, for a second there I thought the comment meant it had to be
asserted for 250 uS before clearing it again. But it's 250 uS before
using the OV490.

Perhaps possible to update the comment a little, but nothing that matters.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>


>  	ret = max9271_configure_gmsl_link(&dev->serializer);
>  	if (ret)
>