Re: [v2 3/3] media: ov8856: Implement sensor module revision identification

Sakari Ailus
2020-03-13T12:45:00Z

Hi Robert,

On Fri, Mar 13, 2020 at 12:03:50PM +0100, Robert Foss wrote:
> Query the sensor for its module revision, and compare it
> to known revisions.
> Currently only the '1B' revision has been added.
>
> Signed-off-by: Robert Foss <robert.foss@linaro.org>
> ---
> drivers/media/i2c/ov8856.c | 54 +++++++++++++++++++++++++++++++++-----
> 1 file changed, 48 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/i2c/ov8856.c b/drivers/media/i2c/ov8856.c
> index db61eed223e8..39662d3d86dd 100644
> --- a/drivers/media/i2c/ov8856.c
> +++ b/drivers/media/i2c/ov8856.c
> @@ -34,6 +34,18 @@
> #define OV8856_MODE_STANDBY 0x00
> #define OV8856_MODE_STREAMING 0x01
>
> +/* define 1B module revision */
> +#define OV8856_1B_MODULE 0x02
> +
> +/* the OTP read-out buffer is at 0x7000 and 0xf is the offset
> + * of the byte in the OTP that means the module revision
> + */
> +#define OV8856_MODULE_REVISION 0x700f
> +#define OV8856_OTP_MODE_CTRL 0x3d84
> +#define OV8856_OTP_LOAD_CTRL 0x3d81
> +#define OV8856_OTP_MODE_AUTO 0x00
> +#define OV8856_OTP_LOAD_CTRL_ENABLE BIT(0)
> +
> /* vertical-timings from sensor */
> #define OV8856_REG_VTS 0x380e
> #define OV8856_VTS_MAX 0x7fff
> @@ -711,6 +723,25 @@ static int ov8856_test_pattern(struct ov8856 *ov8856, u32 pattern)
> OV8856_REG_VALUE_08BIT, pattern);
> }
>
> +static int ov8856_check_revision(struct ov8856 *ov8856)

There are no version checks being done here, nor apparently the version is
read by this function.

> +{
> + int ret;
> +
> + ret = ov8856_write_reg(ov8856, OV8856_REG_MODE_SELECT,
> + OV8856_REG_VALUE_08BIT, OV8856_MODE_STREAMING);
> + if (ret)
> + return ret;
> +
> + ret = ov8856_write_reg(ov8856, OV8856_OTP_MODE_CTRL,
> + OV8856_REG_VALUE_08BIT, OV8856_OTP_MODE_AUTO);
> + if (ret)
> + return ret;
> +
> + return ov8856_write_reg(ov8856, OV8856_OTP_LOAD_CTRL,
> + OV8856_REG_VALUE_08BIT,
> + OV8856_OTP_LOAD_CTRL_ENABLE);

If streaming is started to read the EEPROM, shouldn't it be stopped after
reading it as well?

> +}
> +
> static int ov8856_set_ctrl(struct v4l2_ctrl *ctrl)
> {
> struct ov8856 *ov8856 = container_of(ctrl->handler,
> @@ -1144,6 +1175,23 @@ static int ov8856_identify_module(struct ov8856 *ov8856)
> return -ENXIO;
> }
>
> + /* check sensor hardware revision */
> + ret = ov8856_check_revision(ov8856);
> + if (ret) {
> + dev_err(&client->dev, "failed to check sensor revision");
> + return ret;
> + }
> +
> + ret = ov8856_read_reg(ov8856, OV8856_MODULE_REVISION,
> + OV8856_REG_VALUE_08BIT, &val);
> + if (ret)
> + return ret;

How about moving this inside the check_revision function above? It looks as
if it's dependent on that.

> +
> + dev_info(&client->dev, "OV8856 revision %x (%s) at address 0x%02x\n",
> + val,
> + val == OV8856_1B_MODULE ? "1B" : "unknown revision",
> + client->addr);
> +
> return 0;
> }
>
> @@ -1254,12 +1302,6 @@ static int ov8856_probe(struct i2c_client *client)
> return PTR_ERR(ov8856->xvclk);
> }
>
> - ret = clk_set_rate(ov8856->xvclk, OV8856_XVCLK_24);

This seems like an unrelated change.

> - if (ret < 0) {
> - dev_err(&client->dev, "failed to set xvclk rate (24MHz)\n");
> - return ret;
> - }
> -
> ov8856->reset_gpio = devm_gpiod_get(&client->dev, "reset",
> GPIOD_OUT_HIGH);
> if (IS_ERR(ov8856->reset_gpio)) {

--
Regards,

Sakari Ailus