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Date:   Sat, 20 Mar 2021 18:14:43 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Jacopo Mondi <jacopo+renesas@jmondi.org>
Cc:     kieran.bingham+renesas@ideasonboard.com,
        niklas.soderlund+renesas@ragnatech.se, geert@linux-m68k.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 13/19] media: i2c: rdacm21: Power up OV10640 before
 OV490
Message-ID: <YFYfcwniGswxy9KI@pendragon.ideasonboard.com>
References: <20210319164148.199192-1-jacopo+renesas@jmondi.org>
 <20210319164148.199192-14-jacopo+renesas@jmondi.org>
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In-Reply-To: <20210319164148.199192-14-jacopo+renesas@jmondi.org>
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Hi Jacopo,

Thank you for the patch.

On Fri, Mar 19, 2021 at 05:41:42PM +0100, Jacopo Mondi wrote:
> The current RDACM21 initialization routine powers up the
> OV10640 image sensor after the OV490 ISP. The ISP is programmed with
> a firmware loaded from an embedded EEPROM that (most probably) tries

It's actually a serial flash, not an EEPROM.

> to interact and program also the image sensor connected to the ISP.
> 
> As described in commit ccb26c5742f5 ("media: i2c: rdacm21: Fix OV10640

That commit ID won't be valid anymore once the patches get merged,
unless they are pulled instead of cherry-picked, which is currently not
done in the Linux media subsystem. I'd drop it an only mention the
commit's subject.

> powerup") the image sensor powerdown signal is kept high by an internal
> pull up resistor and occasionally fails to startup correctly if the
> powerdown line is not asserted explicitly. Failures in the OV10640
> startup causes the OV490 firmware to fail to boot correctly resulting in
> the camera module initialization to fail consequentially.
> 
> Fix this by powering up the OV10640 image sensor before testing the
> OV490 firmware boot completion, by splitting the ov10640_initialize()
> function in an ov10640_power_up() one and an ov10640_check_id() one.
> 
> Also make sure the OV10640 identification procedure gives enough time to
> the image sensor to resume after the programming phase performed by the
> OV490 firmware by repeating the ID read procedure,

s/,/./

> 
> This commit fixes a sporadic start-up error triggered by a failure to
> detect the OV490 firmware boot completion:
> rdacm21 8-0054: Timeout waiting for firmware boot
> 
> Fixes: a59f853b3b4b ("media: i2c: Add driver for RDACM21 camera module")
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  drivers/media/i2c/rdacm21.c | 46 ++++++++++++++++++++++++++-----------
>  1 file changed, 32 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> index 3f38c465b348..3763eb690d74 100644
> --- a/drivers/media/i2c/rdacm21.c
> +++ b/drivers/media/i2c/rdacm21.c
> @@ -69,6 +69,7 @@
>  #define OV490_ISP_VSIZE_LOW		0x80820062
>  #define OV490_ISP_VSIZE_HIGH		0x80820063
> 
> +#define OV10640_PID_TIMEOUT		20
>  #define OV10640_ID_HIGH			0xa6
>  #define OV10640_CHIP_ID			0x300a
>  #define OV10640_PIXEL_RATE		55000000
> @@ -314,10 +315,8 @@ static int rdacm21_get_fmt(struct v4l2_subdev *sd,
>  	return 0;
>  }
> 
> -static int ov10640_initialize(struct rdacm21_device *dev)
> +static void ov10640_power_up(struct rdacm21_device *dev)
>  {
> -	u8 val;
> -
>  	/* Enable GPIO0#0 (reset) and GPIO1#0 (pwdn) as output lines. */
>  	ov490_write_reg(dev, OV490_GPIO_SEL0, OV490_GPIO0);
>  	ov490_write_reg(dev, OV490_GPIO_SEL1, OV490_SPWDN0);
> @@ -332,18 +331,35 @@ static int ov10640_initialize(struct rdacm21_device *dev)
>  	usleep_range(1500, 3000);
>  	ov490_write_reg(dev, OV490_GPIO_OUTPUT_VALUE0, OV490_GPIO0);
>  	usleep_range(3000, 5000);
> +}
> 
> -	/* Read OV10640 ID to test communications. */
> -	ov490_write_reg(dev, OV490_SCCB_SLAVE0_DIR, OV490_SCCB_SLAVE_READ);
> -	ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_HIGH, OV10640_CHIP_ID >> 8);
> -	ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_LOW, OV10640_CHIP_ID & 0xff);
> -
> -	/* Trigger SCCB slave transaction and give it some time to complete. */
> -	ov490_write_reg(dev, OV490_HOST_CMD, OV490_HOST_CMD_TRIGGER);
> -	usleep_range(1000, 1500);
> +static int ov10640_check_id(struct rdacm21_device *dev)
> +{
> +	unsigned int i;
> +	u8 val;
> 
> -	ov490_read_reg(dev, OV490_SCCB_SLAVE0_DIR, &val);
> -	if (val != OV10640_ID_HIGH) {
> +	/* Read OV10640 ID to test communications. */
> +	for (i = 0; i < OV10640_PID_TIMEOUT; ++i) {

OV10640_PID_TIMEOUT is used in this function only, I would have made it
local.

> +		ov490_write_reg(dev, OV490_SCCB_SLAVE0_DIR,
> +				OV490_SCCB_SLAVE_READ);
> +		ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_HIGH,
> +				OV10640_CHIP_ID >> 8);
> +		ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_LOW,
> +				OV10640_CHIP_ID & 0xff);
> +
> +		/*
> +		 * Trigger SCCB slave transaction and give it some time
> +		 * to complete.
> +		 */
> +		ov490_write_reg(dev, OV490_HOST_CMD, OV490_HOST_CMD_TRIGGER);
> +		usleep_range(1000, 1500);

It would make sense to create an ov490_sensor_read() function to
encapsulate all this.

It would also be nicer to poll an OV490 register instead of sleeping
blindly. That likely requires the OV490 application note (referenced in
the datasheet), which we don't have. It may be useful to try and get
hold of that. I still feel there may be something a bit fishy, but way
less than before.

> +
> +		ov490_read_reg(dev, OV490_SCCB_SLAVE0_DIR, &val);
> +		if (val == OV10640_ID_HIGH)
> +			break;
> +		usleep_range(1000, 1500);
> +	}

Blank line ?

> +	if (i == OV10640_PID_TIMEOUT) {
>  		dev_err(dev->dev, "OV10640 ID mismatch: (0x%02x)\n", val);
>  		return -ENODEV;
>  	}
> @@ -359,6 +375,8 @@ static int ov490_initialize(struct rdacm21_device *dev)
>  	unsigned int i;
>  	int ret;
> 
> +	ov10640_power_up(dev);

On top of this series, error handling of OV490 writes would make sense.

> +
>  	/*
>  	 * Read OV490 Id to test communications. Give it up to 40msec to
>  	 * exit from reset.
> @@ -396,7 +414,7 @@ static int ov490_initialize(struct rdacm21_device *dev)
>  		return -ENODEV;
>  	}
> 
> -	ret = ov10640_initialize(dev);
> +	ret = ov10640_check_id(dev);
>  	if (ret)
>  		return ret;
> 

-- 
Regards,

Laurent Pinchart