Hi Jacopo,
Thank you for the patch.
On Fri, Mar 19, 2021 at 05:41:48PM +0100, Jacopo Mondi wrote:
> The OV10635 image sensor embedded in the camera module is currently
> reset after the MAX9271 initialization with two long delays that were
> most probably not correctly characterized.
>
> Re-work the image sensor reset procedure by holding the chip in reset
> during the MAX9271 configuration, removing the long sleep delays and
> only wait after the chip exits from reset for 350-500 microseconds
> interval, which is larger than the minimum (2048 * (1 / XVCLK)) timeout
> characterized in the chip manual.
>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> ---
> drivers/media/i2c/rdacm20.c | 29 +++++++++++++++++------------
> 1 file changed, 17 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/media/i2c/rdacm20.c b/drivers/media/i2c/rdacm20.c
> index 7ed3866b5335..7ba2d0249da8 100644
> --- a/drivers/media/i2c/rdacm20.c
> +++ b/drivers/media/i2c/rdacm20.c
> @@ -454,6 +454,19 @@ static int rdacm20_init(struct v4l2_subdev *sd, unsigned int val)
> if (ret)
> return ret;
>
> + /*
> + * Hold OV10635 in reset during max9271 configuration. The reset signal
> + * has to be asserted for at least 200 microseconds.
> + */
> + ret = max9271_enable_gpios(&dev->serializer, MAX9271_GPIO1OUT);
> + if (ret)
> + return ret;
> +
> + ret = max9271_clear_gpios(&dev->serializer, MAX9271_GPIO1OUT);
enable and clear is very cnonfusing. How about mimicking the GPIO API,
with direction_input(), direction_output() and set_value() functions ?
It would also be nice if the polarity could be handled in a nicer way.
There's no GPIO request API here, but maybe a max9271_gpio_set_flags() ?
> + if (ret)
> + return ret;
> + usleep_range(200, 500);
> +
> ret = max9271_configure_gmsl_link(&dev->serializer);
> if (ret)
> return ret;
> @@ -468,22 +481,14 @@ static int rdacm20_init(struct v4l2_subdev *sd, unsigned int val)
> dev->serializer.client->addr = dev->addrs[0];
>
> /*
> - * Reset the sensor by cycling the OV10635 reset signal connected to the
> - * MAX9271 GPIO1 and verify communication with the OV10635.
> + * Release ov10635 from reset and initialize it. The image sensor
> + * requires at least 2048 XVCLK cycles (85 micro-seconds at 24MHz)
> + * before being available. Stay safe and wait up to 500 micro-seconds.
> */
> - ret = max9271_enable_gpios(&dev->serializer, MAX9271_GPIO1OUT);
> - if (ret)
> - return ret;
> -
> - ret = max9271_clear_gpios(&dev->serializer, MAX9271_GPIO1OUT);
> - if (ret)
> - return ret;
> - usleep_range(10000, 15000);
> -
> ret = max9271_set_gpios(&dev->serializer, MAX9271_GPIO1OUT);
> if (ret)
> return ret;
> - usleep_range(10000, 15000);
> + usleep_range(100, 500);
>
> for (i = 0; i < OV10635_PID_TIMEOUT; ++i) {
> ret = ov10635_read16(dev, OV10635_PID);
--
Regards,
Laurent Pinchart
