Re: [PATCH v3 8/9] platform/x86: int3472: Add handshake pin support

[Andy Shevchenko <andy@kernel.org>]

On Wed, Apr 16, 2025 at 02:40:36PM +0200, Hans de Goede wrote:
> New Intel Meteor Lake based laptops with IPU6 cameras have a new type 0x12
> pin defined in the INT3472 sensor companion device which describes
> the sensor's GPIOs.
> 
> This pin is primarily used on designs with a Lattice FPGA chip which is
> capable of running the sensor independently of the main CPU for features
> like presence detection. This pin needs to be driven high to make the FPGA
> run the power-on sequence of the sensor. After driving the pin high,
> the FPGA "firmware" needs 25ms to complete the power-on sequence.
> 
> Add support for this modelling the handshake pin as a GPIO driven "dvdd"
> regulator with a 25 ms enable time. This model was chosen because:
> 
> 1. Sensor chips don't have a handshake pin, so we need to abstract this
>    in some way which does not require modification to the sensor drivers,
>    sensor drivers using the bulk-regulator API to get avdd + vddio + dvdd
>    is normal. So this will work to get the right value set to the handshake
>    pin without requiring sensor driver modifications.
> 
> 2. Sensors typically wait only a small time for the sensor to power-on
>    after de-asserting reset. Not the 25ms the Lattice chip requires.
>    Using the regulator framework's enable_time allows hiding the need for
>    this delay from the sensor drivers.

...

>  			if (ret)
>  				err_msg = "Failed to map regulator to sensor\n";
>  
> +			break;

> +			if (ret)
> +				err_msg = "Failed to map regulator to sensor\n";
> +
>  			break;

As discussed this might be changed to have the same format string with supplied
name as a parameter.

Reviewed-by: Andy Shevchenko <andy@kernel.org>

-- 
With Best Regards,
Andy Shevchenko