linux-kernel - Re: [PATCH 6/8] media: i2c: ov02e10: Implement specification t3 and t5 delays on power-up

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Message-ID: <94bc2fef-1138-4252-9ad3-dd6e01d55290@redhat.com>
Date: Mon, 17 Mar 2025 10:04:50 +0100
From: Hans de Goede <hdegoede@...hat.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>
Cc: Jingjing Xiong <jingjing.xiong@...el.com>, Hao Yao <hao.yao@...el.com>,
 Jim Lai <jim.lai@...el.com>, You-Sheng Yang <vicamo.yang@...onical.com>,
 Alan Stern <stern@...land.harvard.edu>, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org
Subject: Re: [PATCH 6/8] media: i2c: ov02e10: Implement specification t3 and
 t5 delays on power-up

Hi,

On 17-Mar-25 01:39, Bryan O'Donoghue wrote:
> The ov02e10 specification says for power-on:
> 
> t3 = the time between dvdd stable and XSHUTDOWN deassert
> t5 = the time between XSHUTDOWN deassert and SCCB ready
> 
> The power-off path in the spec shows no required delays between XSHUTDONW
> and power-rail shut off so power-off is left alone.
> 
> Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
> ---
>  drivers/media/i2c/ov02e10.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov02e10.c b/drivers/media/i2c/ov02e10.c
> index 9ad70671a718ea0aaf80ad3adcc5738ee57a7ff6..40c4d3ee36e3e2a0bb8be3ff10d016e2bb9bbc9d 100644
> --- a/drivers/media/i2c/ov02e10.c
> +++ b/drivers/media/i2c/ov02e10.c
> @@ -579,7 +579,11 @@ static int ov02e10_power_on(struct device *dev)
>  		goto disable_clk;
>  	}
>  
> -	gpiod_set_value_cansleep(ov02e10->reset, 0);
> +	if (ov02e10->reset) {
> +		usleep_range(5000, 5100);
> +		gpiod_set_value_cansleep(ov02e10->reset, 0);
> +		usleep_range(8000, 8100);
> +	}
>  
>  	return 0;
>  


Note ATM ov02e10->reset is requested with GPIOD_OUT_LOW and it is not
guaranteed that it was high before that. It really should be requested
with GPIOD_OUT_HIGH so that it is guaranteed to be high before
ov02e10_power_on() gets called as the code expects here.

Regards,

Hans