Re: [PATCH] platform/x86: int3472: Add handshake GPIO function

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 10/7/23 04:12, Hao Yao wrote:
> Handshake pin is used for Lattice MIPI aggregator to enable the
> camera sensor. After pulled up, recommend to wail ~250ms to get
> everything ready.

If this is a pin on the "Lattice MIPI aggregator" and
not on the sensor itself then this really should be
modeled as such and should not be registered as a GPIO
consumed by the sensor since the actual sensor does not
have a handshake pin at all.

Also we really don't want to need to patch all involved
sensor drivers to toggle a handshake pin, especially since
the sensor itself does not physically have this pin.

Can you explain a bit more:

1. What the "Lattice MIPI aggregator" is 
2. What its functions are, does this control reset + pwdn
   GPIOs for the sensor? Voltages to the sensor? Clk
   to the sensor ?
3. How the aggregator is connected to both the main
   CPU/SoC as well as how it is connected to the sensor ?
   Some example diagram would be really helpful here.

Then with this info in hand we can try to come up
with a way how to model this.

Assuming this controls the entire power-up sequence
for the sensor then I think it could be modelled
as a GPIO regulator. This also allows making the
regulator core take care of the necessary delay
between setting the GPIO and trying to talk to
the sensor.

Regards,

Hans



> 
> Signed-off-by: Hao Yao <hao.yao@intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/platform/x86/intel/int3472/common.h   | 1 +
>  drivers/platform/x86/intel/int3472/discrete.c | 5 +++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/platform/x86/intel/int3472/common.h b/drivers/platform/x86/intel/int3472/common.h
> index 655ae3ec0593..3ad4c72afb45 100644
> --- a/drivers/platform/x86/intel/int3472/common.h
> +++ b/drivers/platform/x86/intel/int3472/common.h
> @@ -23,6 +23,7 @@
>  #define INT3472_GPIO_TYPE_POWER_ENABLE				0x0b
>  #define INT3472_GPIO_TYPE_CLK_ENABLE				0x0c
>  #define INT3472_GPIO_TYPE_PRIVACY_LED				0x0d
> +#define INT3472_GPIO_TYPE_HANDSHAKE				0x12
>  
>  #define INT3472_PDEV_MAX_NAME_LEN				23
>  #define INT3472_MAX_SENSOR_GPIOS				3
> diff --git a/drivers/platform/x86/intel/int3472/discrete.c b/drivers/platform/x86/intel/int3472/discrete.c
> index b644ce65c990..4753161b4080 100644
> --- a/drivers/platform/x86/intel/int3472/discrete.c
> +++ b/drivers/platform/x86/intel/int3472/discrete.c
> @@ -111,6 +111,10 @@ static void int3472_get_func_and_polarity(u8 type, const char **func, u32 *polar
>  		*func = "power-enable";
>  		*polarity = GPIO_ACTIVE_HIGH;
>  		break;
> +	case INT3472_GPIO_TYPE_HANDSHAKE:
> +		*func = "handshake";
> +		*polarity = GPIO_ACTIVE_HIGH;
> +		break;
>  	default:
>  		*func = "unknown";
>  		*polarity = GPIO_ACTIVE_HIGH;
> @@ -201,6 +205,7 @@ static int skl_int3472_handle_gpio_resources(struct acpi_resource *ares,
>  	switch (type) {
>  	case INT3472_GPIO_TYPE_RESET:
>  	case INT3472_GPIO_TYPE_POWERDOWN:
> +	case INT3472_GPIO_TYPE_HANDSHAKE:
>  		ret = skl_int3472_map_gpio_to_sensor(int3472, agpio, func, polarity);
>  		if (ret)
>  			err_msg = "Failed to map GPIO pin to sensor\n";