drivers: power_domain: introduce nrf_gpio_pad_group

Introduce the NRF GPIO Pad Group device driver and binding. The
pad group device represents the GPIO pads (pins), contrary to a
GPIO controller, which is one of the many devices which can be
muxed to pads in the pad group.

The pad group belong to a power domain, which is not neccesarily the
same power domain as devices being muxed to the pads, like GPIO or
UART. If no ACTIVE device is using any of the pads in the pad
group, the pad groups power domain may be SUSPENDED. Before the pad
groups power domain is SUSPENDED, pad config retention must be
enabled to prevent the pads from loosing their state. That's what
this device driver manages. Once retained, the pad configs and
outputs are locked, even when their power domain is SUSPENDED.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>

Author: bjarki-andreasen

drivers/power_domain/CMakeLists.txt

@@ -9,5 +9,6 @@ zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_INTEL_ADSP power_domain_intel_a
 zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_NXP_SCU power_domain_nxp_scu.c)
 zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_NRFS_GDPWR power_domain_nrfs_gdpwr.c)
 zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_NRFS_SWEXT power_domain_nrfs_swext.c)
+zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_NRF_GPIO_PAD_GROUP power_domain_nrf_gpio_pad_group.c)
 zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_SOC_PM_STATE power_domain_soc_state_change.c)
 zephyr_library_sources_ifdef(CONFIG_POWER_DOMAIN_TISCI power_domain_tisci.c)

drivers/power_domain/Kconfig

@@ -125,5 +125,6 @@ endif #POWER_DOMAIN_TISCI
 
 rsource "Kconfig.nrfs_gdpwr"
 rsource "Kconfig.nrfs_swext"
+rsource "Kconfig.nrf_gpio_pad_group"
 
 endif

drivers/power_domain/Kconfig.nrf_gpio_pad_group

@@ -0,0 +1,7 @@
+# Copyright 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+config POWER_DOMAIN_NRF_GPIO_PAD_GROUP
+	bool "NRFS Global Domain Power Request driver"
+	depends on DT_HAS_NORDIC_NRF_GPIO_PAD_GROUP_ENABLED
+	default y

drivers/power_domain/power_domain_nrf_gpio_pad_group.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT nordic_nrf_gpio_pad_group
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/pm/device.h>
+#include <zephyr/logging/log.h>
+
+#include <hal/nrf_gpio.h>
+
+LOG_MODULE_REGISTER(nrf_gpio_pad_group, CONFIG_POWER_DOMAIN_LOG_LEVEL);
+
+struct nrf_port_retain_config {
+	NRF_GPIO_Type *regs;
+	uint32_t retain_mask;
+};
+
+static void nrf_port_retain_driver_turn_off(const struct device *dev)
+{
+	const struct nrf_port_retain_config *dev_config = dev->config;
+
+	LOG_DBG("%s pads 0x%08x retain %s", dev->name, dev_config->retain_mask, "enable");
+	nrf_gpio_port_retain_enable(dev_config->regs, dev_config->retain_mask);
+}
+
+static void nrf_port_retain_driver_turn_on(const struct device *dev)
+{
+	const struct nrf_port_retain_config *dev_config = dev->config;
+
+	LOG_DBG("%s pads 0x%08x retain %s", dev->name, dev_config->retain_mask, "disable");
+	nrf_gpio_port_retain_disable(dev_config->regs, dev_config->retain_mask);
+}
+
+static int nrf_port_retain_driver_pm_action(const struct device *dev,
+					    enum pm_device_action action)
+{
+	switch (action) {
+	case PM_DEVICE_ACTION_TURN_OFF:
+		nrf_port_retain_driver_turn_off(dev);
+		break;
+
+	case PM_DEVICE_ACTION_TURN_ON:
+		nrf_port_retain_driver_turn_on(dev);
+		break;
+
+	default:
+		break;
+	};
+
+	return 0;
+}
+
+static int nrf_port_retain_driver_init(const struct device *dev)
+{
+	return pm_device_driver_init(dev, nrf_port_retain_driver_pm_action);
+}
+
+#define NRF_GPIO_PAD_GROUP_DEFINE(inst)								\
+	static const struct nrf_port_retain_config _CONCAT(config, inst) = {			\
+		.regs = (NRF_GPIO_Type *)DT_REG_ADDR(DT_INST_PARENT(inst)),			\
+		.retain_mask = DT_PROP_OR(inst, retain_mask, UINT32_MAX),			\
+	};											\
+												\
+	PM_DEVICE_DT_INST_DEFINE(inst, nrf_port_retain_driver_pm_action);			\
+												\
+	DEVICE_DT_INST_DEFINE(									\
+		inst,										\
+		nrf_port_retain_driver_init,							\
+		PM_DEVICE_DT_INST_GET(inst),							\
+		NULL,										\
+		&_CONCAT(config, inst),								\
+		PRE_KERNEL_1,									\
+		UTIL_INC(CONFIG_GPIO_INIT_PRIORITY),						\
+		NULL										\
+	);
+
+DT_INST_FOREACH_STATUS_OKAY(NRF_GPIO_PAD_GROUP_DEFINE)

dts/bindings/gpio/nordic,nrf-gpio-pad-group.yaml

@@ -0,0 +1,43 @@
+# Copyright 2025 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+  Nordic nRF GPIO pad group.
+
+  The GPIO pad group describes the pads (package
+  pins of the SoC) the GPIO controller manages.
+
+  The pads may be in a different power domain than
+  the GPIO controller, and may require enabling
+  retention to preserve the GPIO configuration if
+  the power domain is suspended.
+
+  The GPIO pad group is a child node of the GPIO
+  controller which manages the the pad group,
+  named pad-group. The pad group's nodelabel is
+  named gpio_pad_group<GPIO number>.
+
+  Example layout:
+
+    gpio0: gpio@938000 {
+            compatible = "nordic,nrf-gpio";
+
+            ...
+
+            gpio_pad_group0: pad-group {
+                    compatible = "nordic,nrf-gpio-pad-group";
+                    power-domains = <&gdpwr_slow_main>;
+                    retain-mask = <0xFFF>;
+            };
+    };
+
+compatible: "nordic,nrf-gpio-pad-group"
+
+include: base.yaml
+
+properties:
+  retain-mask:
+    type: int
+    description: |
+      Mask of pins which shall be retained if pad
+      group's power domain is powered off.