linux-kernel - Re: [PATCH 09/16] media: i2c: rdacm21: Re-work OV10640 initialization

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Date:   Wed, 17 Feb 2021 13:55:40 +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 09/16] media: i2c: rdacm21: Re-work OV10640 initialization

Hi Jacopo,

On 16/02/2021 17:41, Jacopo Mondi wrote:
> The OV10640 image sensor reset and powerdown on signals are controlled
> by the embedded OV490 ISP. The current reset procedure does not respect
> the 1 millisecond power-up delay and releases the reset signal before
> the powerdown one.
> 
> Fix the OV10640 power up sequence by releasing the powerdown signal,
> waiting the mandatory 1 millisecond power up delay and then releasing
> the reset signal. The reset delay is not characterized in the chip
> manual if not as "255 XVCLK + initialization". Wait for at least 3
> milliseconds to guarantee the SCCB bus is available.
> 
> This commit fixes a sporadic start-up error triggered by a failure to
> read the OV10640 chip ID:
> rdacm21 8-0054: OV10640 ID mismatch: (0x01)

Have you done a similar initialisation rework for the RDACM21 as you do
in [03/16] of this series for the RDACM20 (or was it already better
perhaps?)

Only interested because of noting that I think the 'mismatch' check is
now gone from the RDAMC20.


> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> ---
>  drivers/media/i2c/rdacm21.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> index b22a2ca5340b..c420a6b96879 100644
> --- a/drivers/media/i2c/rdacm21.c
> +++ b/drivers/media/i2c/rdacm21.c
> @@ -333,13 +333,15 @@ static int ov10640_initialize(struct rdacm21_device *dev)
>  {
>  	u8 val;
>  
> -	/* Power-up OV10640 by setting RESETB and PWDNB pins high. */
> +	/* Power-up OV10640 by setting PWDNB and RESETB pins high. */
>  	ov490_write_reg(dev, OV490_GPIO_SEL0, OV490_GPIO0);
>  	ov490_write_reg(dev, OV490_GPIO_SEL1, OV490_SPWDN0);
>  	ov490_write_reg(dev, OV490_GPIO_DIRECTION0, OV490_GPIO0);
>  	ov490_write_reg(dev, OV490_GPIO_DIRECTION1, OV490_SPWDN0);
> -	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_GPIO0);
> +
>  	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_SPWDN0);
> +	usleep_range(1500, 3000);
> +	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_GPIO0);
>  	usleep_range(3000, 5000);
>  
>  	/* Read OV10640 ID to test communications. */
>