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

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Date:   Sat, 20 Mar 2021 17:52:18 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org,
        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,

Thank you for the patch.

On Fri, Mar 19, 2021 at 04:49:44PM +0000, Kieran Bingham wrote:
> 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.

The commit message and comment should match the code, especially given
that I'm not sure here which of the two is actually incorrect. I suspect
the sleep is actually in the wrong location.

> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> 
> 
> >  	ret = max9271_configure_gmsl_link(&dev->serializer);
> >  	if (ret)
> > 

-- 
Regards,

Laurent Pinchart