linux-kernel - Re: [PATCH v2 11/18] media: i2c: rdacm21: Fix OV10640 powerdown

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Date:   Mon, 15 Mar 2021 17:20:16 +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 v2 11/18] media: i2c: rdacm21: Fix OV10640 powerdown

Hi Jacopo,

On 15/03/2021 13:15, Jacopo Mondi wrote:
> The OV10640 image sensor powerdown signal is controlled by the first
> line of the OV490 GPIO pad #1, but the pad #0 identifier
> OV490_GPIO_OUTPUT_VALUE0 was erroneously used. As a result the image
> sensor powerdown signal was never asserted but was kept high by an
> internal pull-up resistor, causing sporadic failures during the
> image sensor startup phase.
> 
> Fix this by using the correct GPIO pad identifier.
> 
> While at it also fix the GPIO signal handling sequence, as the reset
> line was released before the powerdown one, and introduce the correct
> delays in between the two operations.
> 
> Wait the mandatory 1 millisecond delay after the powerup lane is

Technically you wait 1.5 milliseconds below - but I think that's fine
here ;-)

> asserted. 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)
> 
> Fixes: a59f853b3b4b ("media: i2c: Add driver for RDACM21 camera module")
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

Sometime it might be nice to see this look more like the GPIO
interfaces, but I think this is fine for now.

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

> ---
>  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 7bce55adfd7c..50a9b0d8255d 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_VALUE1, OV490_SPWDN0);
> +	usleep_range(1500, 3000);
>  	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_GPIO0);
> -	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_SPWDN0);
>  	usleep_range(3000, 5000);
>  
>  	/* Read OV10640 ID to test communications. */
>