linux-kernel - Re: [PATCH 1/4] media: i2c: ov2685: Make reset gpio optional

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Message-ID: <2543677.Lt9SDvczpP@g550jk>
Date:   Sun, 29 Jan 2023 12:49:03 +0100
From:   Luca Weiss <luca@...tu.xyz>
To:     Jacopo Mondi <jacopo.mondi@...asonboard.com>
Cc:     ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        Shunqian Zheng <zhengsq@...k-chips.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jacopo Mondi <jacopo.mondi@...asonboard.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] media: i2c: ov2685: Make reset gpio optional

On Sonntag, 29. Jänner 2023 12:22:49 CET Jacopo Mondi wrote:
> Hi Luca
> 
> On Sun, Jan 29, 2023 at 10:42:35AM +0100, Luca Weiss wrote:
> > In some setups XSHUTDOWN is connected to DOVDD when it's unused,
> > therefore treat the reset gpio as optional.
> 
> I don't have a datasheet for this sensor, but OV sensors usually have
> to gpio lines to control powerdown and reset. Datasheets usually
> suggest to hook one of the 2 to DOVDD and control the other from the
> SoC. How is the sensor hooked up in your design ? No gpio lines is
> controlled by the SoC ?

It looks like this sensor only has XSHUTDOWN pin and no extra reset pin.

In my setup there's the normal I2C & CSI & mclk hookups, but the supply lines 
and shutdown line are all just connected to regulator-fixed, so gpio-
controlled on/off regulators.

> 
> Another question is if we need to software-reset the sensor if no gpio
> line is hooked up to XSHUTDOWN.

The datasheet mentions it resets itself during power up (so when the supplies 
are turned on), so I don't think we need to add anything.

Regards
Luca

> 
> > Signed-off-by: Luca Weiss <luca@...tu.xyz>
> > ---
> > 
> >  drivers/media/i2c/ov2685.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/i2c/ov2685.c b/drivers/media/i2c/ov2685.c
> > index a3b524f15d89..a422f4c8a2eb 100644
> > --- a/drivers/media/i2c/ov2685.c
> > +++ b/drivers/media/i2c/ov2685.c
> > @@ -734,7 +734,7 @@ static int ov2685_probe(struct i2c_client *client,
> > 
> >  	if (clk_get_rate(ov2685->xvclk) != OV2685_XVCLK_FREQ)
> >  	
> >  		dev_warn(dev, "xvclk mismatched, modes are based on 
24MHz\n");
> > 
> > -	ov2685->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> > +	ov2685->reset_gpio = devm_gpiod_get_optional(dev, "reset",
> > GPIOD_OUT_LOW);> 
> >  	if (IS_ERR(ov2685->reset_gpio)) {
> >  	
> >  		dev_err(dev, "Failed to get reset-gpios\n");
> >  		return -EINVAL;
> > 
> > --
> > 2.39.1