platform/x86: int3472: Add handshake pin support

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.

Link: https://lore.kernel.org/platform-driver-x86/[email protected]/
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2341731
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Hans de Goede <[email protected]>
Tested-by: David Heidelberg <[email protected]>  # Dell Latitude 9440
Reviewed-by: Sakari Ailus <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Ilpo Järvinen <[email protected]>
Signed-off-by: Ilpo Järvinen <[email protected]>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/platform/x86/intel/int3472/discrete.c b/drivers/platform/x86/intel/int3472/discrete.c
index a2db4fae0e6d..bcc7bb122a56 100644
--- a/drivers/platform/x86/intel/int3472/discrete.c
+++ b/drivers/platform/x86/intel/int3472/discrete.c
@@ -191,6 +191,10 @@ static void int3472_get_con_id_and_polarity(struct acpi_device *adev, u8 *type,
 		*con_id = "avdd";
 		*gpio_flags = GPIO_ACTIVE_HIGH;
 		break;
+	case INT3472_GPIO_TYPE_HANDSHAKE:
+		*con_id = "dvdd";
+		*gpio_flags = GPIO_ACTIVE_HIGH;
+		break;
 	default:
 		*con_id = "unknown";
 		*gpio_flags = GPIO_ACTIVE_HIGH;
@@ -290,6 +294,7 @@ static int skl_int3472_handle_gpio_resources(struct acpi_resource *ares,
 	case INT3472_GPIO_TYPE_CLK_ENABLE:
 	case INT3472_GPIO_TYPE_PRIVACY_LED:
 	case INT3472_GPIO_TYPE_POWER_ENABLE:
+	case INT3472_GPIO_TYPE_HANDSHAKE:
 		gpio = skl_int3472_gpiod_get_from_temp_lookup(int3472, agpio, con_id, gpio_flags);
 		if (IS_ERR(gpio)) {
 			ret = PTR_ERR(gpio);
@@ -316,7 +321,16 @@ static int skl_int3472_handle_gpio_resources(struct acpi_resource *ares,
 							     con_id,
 							     int3472->quirks.avdd_second_sensor);
 			if (ret)
-				err_msg = "Failed to map regulator to sensor\n";
+				err_msg = "Failed to map power-enable to sensor\n";
+
+			break;
+		case INT3472_GPIO_TYPE_HANDSHAKE:
+			/* Setups using a handshake pin need 25 ms enable delay */
+			ret = skl_int3472_register_regulator(int3472, gpio,
+							     25 * USEC_PER_MSEC,
+							     con_id, NULL);
+			if (ret)
+				err_msg = "Failed to map handshake to sensor\n";
 
 			break;
 		default: /* Never reached */