devicetree: define low-power GPIO configurations

[pabigot]

Configuration of a device to low-power mode generally requires GPIO pin settings that are not power-on defaults. These settings are necessary even in situations where the connected peripheral is not in use, and require flags that are not part of the Linux standard devicetree flags supported in #16648. Examples for the Nordic Thingy:52 (nrf52_pca20020) are in a comment below.

Ideally these flags should be associated with the GPIO pins in devicetree, with the settings applied when the corresponding GPIO controller is initialized.

They must also be visible in the power management structure so when a device that uses the GPIO powers down the low-power configuration is restored.

[pabigot]

Below are pin configurations for the nrf52_pca20020 platform that are required to get sleep current below 100 uA. These are informed by the reference implementation and have been validated in Zephyr in work-in-progress based on the new GPIO API. Some of them may not be necessary, others (unclear exactly which) are necessary.

const struct pin_s p0_pins[] = {
	{"XL1", GPIO_OUTPUT_LOW},
	{"XL2", GPIO_OUTPUT_LOW},
	{"DIG0", GPIO_PULL_DOWN},
	{"DIG1", GPIO_PULL_DOWN},

	{"DIG2", GPIO_PULL_DOWN},
	{"IOX_OSCIO", GPIO_PULL_DOWN},
	{"MPU_INT", GPIO_PULL_DOWN},
	{"SDA", 0}, // H0H1

	{"SCL", 0}, // H0H1
	{"NFC1", 0},
	{"NFC2", 0},
	{"BUTTON", GPIO_INPUT | GPIO_PULL_UP}, // double level

	{"LIS_INT1", 0},
	{"USB_DETECT", GPIO_INPUT}, // S0H1
	{"SDA_EXT", 0}, // H0H1
	{"SCL_EXT", 0}, // H0H1

	{"IOX_RESETn", GPIO_OUTPUT_HIGH},
	{"BAT_CHG_STAT", GPIO_INPUT},
	{"MOS_1", GPIO_OUTPUT_LOW},
	{"MOS_2", GPIO_OUTPUT_LOW},

	{"MOS_3", GPIO_OUTPUT_LOW},
	{"MOS_4", GPIO_OUTPUT_LOW},
	{"CCS_INT", GPIO_PULL_DOWN},
	{"LPS_INT", GPIO_INPUT},

	{"HTS_INT", GPIO_PULL_DOWN},
	{"MIC_DOUT", GPIO_INPUT | GPIO_PULL_DOWN},
	{"MIC_CLK", GPIO_OUTPUT_LOW},
	{"SPEAKER", GPIO_OUTPUT_LOW},

	{"BATTERY", GPIO_INPUT},
	{"SPK_PWR_CTRL", GPIO_OUTPUT_LOW},
	{"VDD_PWR_CTRL", GPIO_OUTPUT_HIGH},
	{"BH_INT", GPIO_PULL_DOWN},
};

const struct pin_s iox_pins[] = {
	{"IOEXT0", GPIO_OUTPUT_LOW},
	{"IOEXT1", GPIO_OUTPUT_LOW},
	{"IOEXT2", GPIO_OUTPUT_LOW},
	{"IOEXT3", GPIO_OUTPUT_LOW},
	{"BAT_MON_EN", GPIO_OUTPUT_LOW},
	{"LIGHTWELL_G", GPIO_OUTPUT_HIGH},
	{"LIGHTWELL_B", GPIO_OUTPUT_HIGH},
	{"LIGHTWELL_R", GPIO_OUTPUT_HIGH},
	{"MPU_PWR_CTRL", GPIO_OUTPUT_LOW},
	{"MIC_PWR_CTRL", GPIO_OUTPUT_LOW},
	{"CCS_PWR_CTRL", GPIO_OUTPUT_LOW},
	{"CCS_RESETn", GPIO_OUTPUT_LOW},
	{"CCS_WAKEn", GPIO_OUTPUT_LOW},
	{"SENSE_R", GPIO_OUTPUT_HIGH},
	{"SENSE_G", GPIO_OUTPUT_HIGH},
	{"SENSE_B", GPIO_OUTPUT_HIGH},
};

[gmarull]

This can now be achieved with pinctrl by using a sleep state with appropriate configuration. Reference guide available here: https://docs.zephyrproject.org/latest/guides/pinctrl/index.html