soc/arm/silabs_exx32: fix PM implementation - wake up using BURTC timer

- Add Gecko BURTC sys_clock driver to handle wake up from EM2,3 states
- Remove custom PM policy and dependency on HAL sl_power_manager service
- EM1 supported in all configurations
- EM2,3 supported only if SysTick is replaced by BURTC

Signed-off-by: Roman Dobrodii <rdobrodii@antmicro.com>

boards/arm/efr32_thunderboard/board.c

@@ -50,7 +50,6 @@ static int thunderboard_init_clocks(void)
 	CMU_ClockSelectSet(cmuClock_EM01GRPBCLK, cmuSelect_HFRCODPLL);
 #endif
 	CMU_ClockSelectSet(cmuClock_EM23GRPACLK, cmuSelect_LFRCO);
-	CMU_ClockSelectSet(cmuClock_EM4GRPACLK, cmuSelect_LFRCO);
 #if defined(RTCC_PRESENT)
 	CMU_ClockSelectSet(cmuClock_RTCC, cmuSelect_LFRCO);
 #endif

boards/arm/efr32_thunderboard/efr32bg22_brd4184a_defconfig

@@ -6,12 +6,17 @@ CONFIG_BOARD_EFR32BG22_BRD4184A=y
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y
 CONFIG_SERIAL=y
-CONFIG_CORTEX_M_SYSTICK=y
 CONFIG_GPIO=y
-CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=76800000
-CONFIG_CMU_HFCLK_HFXO=y
 CONFIG_SOC_GECKO_EMU_DCDC=y
 CONFIG_SOC_GECKO_EMU_DCDC_MODE_ON=y
 CONFIG_HW_STACK_PROTECTION=y
-CONFIG_CMU_HFCLK_HFRCO=y
 CONFIG_PINCTRL=y
+
+# Used if SysTick is enabled, ignored for BURTC
+# (BURTC uses TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
+CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=76800000
+
+# Use BURTC as system clock source
+CONFIG_GECKO_BURTC_TIMER=y
+CONFIG_CMU_BURTCCLK_LFXO=y
+CONFIG_SYS_CLOCK_TICKS_PER_SEC=1024

boards/arm/efr32_thunderboard/efr32bg27_brd2602a_defconfig

@@ -6,12 +6,17 @@ CONFIG_BOARD_EFR32BG27_BRD2602A=y
 CONFIG_CONSOLE=y
 CONFIG_UART_CONSOLE=y
 CONFIG_SERIAL=y
-CONFIG_CORTEX_M_SYSTICK=y
 CONFIG_GPIO=y
-CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=76800000
-CONFIG_CMU_HFCLK_HFXO=y
 CONFIG_SOC_GECKO_EMU_DCDC=y
 CONFIG_SOC_GECKO_EMU_DCDC_MODE_ON=y
 CONFIG_HW_STACK_PROTECTION=y
-CONFIG_CMU_HFCLK_HFRCO=y
 CONFIG_PINCTRL=y
+
+# Used if SysTick is enabled, ignored for BURTC
+# (BURTC uses TIMER_READS_ITS_FREQUENCY_AT_RUNTIME)
+CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=76800000
+
+# Use BURTC as system clock source
+CONFIG_GECKO_BURTC_TIMER=y
+CONFIG_CMU_BURTCCLK_LFXO=y
+CONFIG_SYS_CLOCK_TICKS_PER_SEC=1024

boards/arm/efr32_thunderboard/thunderboard.dtsi

@@ -47,6 +47,10 @@
 
 &cpu0 {
 	clock-frequency = <76800000>;
+	/* Enable EM1,2. This means BURTC has to be used as sys_clock
+	 * or the system won't wake up
+	 */
+	cpu-power-states = <&pstate_em1 &pstate_em2>;
 };
 
 &usart0 {
@@ -107,6 +111,10 @@
 	status = "okay";
 };
 
+&burtc0 {
+	status = "okay";
+};
+
 &stimer0 {
 	status = "okay";
 };

drivers/timer/CMakeLists.txt

@@ -11,6 +11,7 @@ zephyr_library_sources_ifdef(CONFIG_INTEL_ADSP_TIMER intel_adsp_timer.c)
 zephyr_library_sources_ifdef(CONFIG_CC13X2_CC26X2_RTC_TIMER cc13x2_cc26x2_rtc_timer.c)
 zephyr_library_sources_ifdef(CONFIG_CORTEX_M_SYSTICK cortex_m_systick.c)
 zephyr_library_sources_ifdef(CONFIG_ESP32C3_SYS_TIMER esp32c3_sys_timer.c)
+zephyr_library_sources_ifdef(CONFIG_GECKO_BURTC_TIMER gecko_burtc_timer.c)
 zephyr_library_sources_ifdef(CONFIG_HPET_TIMER hpet.c)
 zephyr_library_sources_ifdef(CONFIG_ITE_IT8XXX2_TIMER ite_it8xxx2_timer.c)
 zephyr_library_sources_ifdef(CONFIG_LEON_GPTIMER leon_gptimer.c)

drivers/timer/Kconfig

@@ -71,6 +71,7 @@ source "drivers/timer/Kconfig.cavs"
 source "drivers/timer/Kconfig.cc13x2_cc26x2_rtc"
 source "drivers/timer/Kconfig.cortex_m_systick"
 source "drivers/timer/Kconfig.esp32c3_sys"
+source "drivers/timer/Kconfig.gecko"
 source "drivers/timer/Kconfig.hpet"
 source "drivers/timer/Kconfig.ite_it8xxx2"
 source "drivers/timer/Kconfig.leon_gptimer"

drivers/timer/Kconfig.gecko

@@ -0,0 +1,33 @@
+# Copyright (c) 2023 Antmicro <www.antmicro.com>
+# SPDX-License-Identifier: Apache-2.0
+
+config GECKO_BURTC_TIMER
+	bool "SiLabs Gecko BURTC system clock driver"
+	depends on SOC_GECKO_SERIES2
+	depends on DT_HAS_SILABS_GECKO_BURTC_ENABLED
+	select SOC_GECKO_BURTC
+	select TICKLESS_CAPABLE
+	select TIMER_READS_ITS_FREQUENCY_AT_RUNTIME
+	help
+	  If you enable this, BURTC will be used to provide hw_cycles and
+	  kernel ticks instead of Cortex-M SysTick. You need this for system
+	  to be able to keep track of time and wake up from EM2 & EM3 sleep
+	  states.
+
+	  NOTE:
+	  Using BURTC instead of SysTick has a large impact on kernel timing
+	  precision.
+	  1. You won't be able to use the usual 0.1ms-granularity tickless
+	     scheduling. Kernel tick duration should be at least 6 BURTC clock
+	     cycles, that is ~183 us @ 32768 Hz (LFXO, LFRCO) or
+	     ~6 ms @ 1000 Hz (ULFRCO).
+	  2. In general, accuracy of real-time scheduling by kernel will be
+	     degraded: all timeout-based facilities, such as timers, delayable
+	     work, k_sleep, will issue thread wake ups less precisely than when
+	     using SysTick timer.
+	  3. hw_cycles granularity will be equal to 1 BURTC clock, that is
+	     ~31 us @ 32768 Hz or ~1 ms @ 1000 Hz. This reduces timing
+	     precision of all code which relies on cycles API, e.g.
+	     k_cycle_get_32() and similar functions.
+
+	  If unsure, say 'N'.

drivers/timer/gecko_burtc_timer.c

@@ -0,0 +1,237 @@
+/*
+ * Copyright (c) 2023 Antmicro <www.antmicro.com>
+ *
+ * Based on:
+ *  sam0_rtc_timer.c Copyright (c) 2018 omSquare s.r.o.
+ *  intel_adsp_timer.c Copyright (c) 2020 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT silabs_gecko_burtc
+
+/**
+ * @file
+ * @brief SiLabs Gecko BURTC-based sys_clock driver
+ *
+ */
+
+#include <zephyr/device.h>
+#include <soc.h>
+#include <zephyr/drivers/clock_control.h>
+#include <zephyr/drivers/timer/system_timer.h>
+#include <zephyr/drivers/pinctrl.h>
+#include <zephyr/sys_clock.h>
+#include <zephyr/irq.h>
+#include <zephyr/spinlock.h>
+#include <zephyr/logging/log.h>
+
+#include "em_device.h"
+#include "em_cmu.h"
+#include "em_burtc.h"
+
+
+LOG_MODULE_REGISTER(gecko_burtc_timer);
+
+
+/* Maximum time interval between timer interrupts (in hw_cycles) */
+#define MAX_TIMEOUT_CYC (UINT32_MAX >> 1)
+
+/*
+ * Mininum time interval between now and IRQ firing that can be scheduled.
+ * The main cause for this is LFSYNC register update, which requires several
+ * LF clk cycles for synchronization.
+ * Seee e.g. "4.2.4.4.4 LFSYNC Registers" in "EFR32xG22 Reference Manual"
+ */
+#define MIN_DELAY_CYC (6u)
+
+#define TIMER_IRQ (DT_INST_IRQN(0))
+
+#if defined(CONFIG_TEST)
+/* See tests/kernel/context */
+const int32_t z_sys_timer_irq_for_test = TIMER_IRQ;
+#endif
+
+/* With CONFIG_TIMER_READS_ITS_FREQUENCY_AT_RUNTIME, that's where we
+ * should write hw_cycles timer clock frequency upon init
+ */
+extern int z_clock_hw_cycles_per_sec;
+
+/* Number of hw_cycles clocks per 1 kernel tick */
+static uint32_t g_cyc_per_tick;
+
+/* MAX_TIMEOUT_CYC expressed as ticks */
+static uint32_t g_max_timeout_ticks;
+
+/* Value of BURTC counter when the previous kernel tick was announced */
+static atomic_t g_last_count;
+
+/* Spinlock to sync between Compare ISR and update of Compare register */
+static struct k_spinlock g_lock;
+
+
+static void burtc_isr(const void *arg)
+{
+	ARG_UNUSED(arg);
+
+	/* Clear the interrupt */
+	BURTC_IntClear(BURTC_IF_COMP);
+
+	uint32_t curr = BURTC_CounterGet();
+
+	/* NOTE: this is the only place where g_last_count is modified,
+	 * so we don't need to do make the whole read-and-modify atomic, just
+	 * writing it behind the memory barrier is enough
+	 */
+	uint32_t prev = atomic_get(&g_last_count);
+
+	/* How many ticks have we not announced since the last announcement */
+	uint32_t unannounced = (curr - prev) / g_cyc_per_tick;
+
+	atomic_set(&g_last_count, prev + unannounced * g_cyc_per_tick);
+
+	if (!IS_ENABLED(CONFIG_TICKLESS_KERNEL)) {
+		/* Counter value on which announcement should be made */
+		uint32_t next = prev + g_cyc_per_tick;
+
+		/* `next` can be too close in the future since we're trying to
+		 * announce the very next tick - in that case we skip one and
+		 * announce the one after it instead
+		 */
+		if ((next - curr) < MIN_DELAY_CYC) {
+			next += g_cyc_per_tick;
+		}
+
+		BURTC_CompareSet(0, next);
+	}
+
+	sys_clock_announce(unannounced);
+}
+
+void sys_clock_set_timeout(int32_t ticks, bool idle)
+{
+	ARG_UNUSED(idle);
+
+	if (!IS_ENABLED(CONFIG_TICKLESS_KERNEL)) {
+		return;
+	}
+
+	/*
+	 * calculate 'ticks' value that specifies which tick to announce,
+	 * beginning from the closest upcoming one:
+	 * 0 - announce upcoming tick itself
+	 * 1 - skip upcoming one, but announce the one after it, etc.
+	 */
+	ticks = (ticks == K_TICKS_FOREVER) ? g_max_timeout_ticks : ticks;
+	ticks = CLAMP(ticks - 1, 0, g_max_timeout_ticks);
+
+	k_spinlock_key_t key = k_spin_lock(&g_lock);
+
+	uint32_t curr = BURTC_CounterGet();
+	uint32_t prev = atomic_get(&g_last_count);
+
+	/* How many ticks have we not announced since the last announcement */
+	uint32_t unannounced = (curr - prev) / g_cyc_per_tick;
+
+	/* Which tick to announce (counting from the last announced one) */
+	uint32_t to_announce = unannounced + ticks + 1;
+
+	/* Force maximum interval between announcements. If we sit without
+	 * announcements for too long, counter will roll over and we'll lose
+	 * track of unannounced ticks.
+	 */
+	to_announce = MIN(to_announce, g_max_timeout_ticks);
+
+	/* Counter value on which announcement should be made */
+	uint32_t next = prev + to_announce * g_cyc_per_tick;
+
+	/* `next` can be too close in the future if we're trying to announce
+	 * the very next tick - in that case we skip one and announce the one
+	 * after it instead
+	 */
+	if ((next - curr) < MIN_DELAY_CYC) {
+		next += g_cyc_per_tick;
+	}
+
+	BURTC_CompareSet(0, next);
+	k_spin_unlock(&g_lock, key);
+}
+
+uint32_t sys_clock_elapsed(void)
+{
+	if (!IS_ENABLED(CONFIG_TICKLESS_KERNEL)) {
+		return 0;
+	} else {
+		return (BURTC_CounterGet() - g_last_count) / g_cyc_per_tick;
+	}
+}
+
+uint32_t sys_clock_cycle_get_32(void)
+{
+	/* API note: this function is unrelated to kernel ticks, it returns
+	 * a value of some 32-bit hw_cycles counter which counts with
+	 * z_clock_hw_cycles_per_sec frequency
+	 */
+	return BURTC_CounterGet();
+}
+
+static int burtc_init(void)
+{
+	uint32_t hw_clock_freq;
+	BURTC_Init_TypeDef init = BURTC_INIT_DEFAULT;
+
+	/* Enable clock for BURTC CSRs on APB */
+	CMU_ClockEnable(cmuClock_BURTC, true);
+
+	/* Configure BURTC LF clocksource according to Kconfig */
+#if defined(CONFIG_CMU_BURTCCLK_LFXO)
+	CMU_ClockSelectSet(cmuClock_BURTC, cmuSelect_LFXO);
+#elif defined(CONFIG_CMU_BURTCCLK_LFRCO)
+	CMU_ClockSelectSet(cmuClock_BURTC, cmuSelect_LFRCO);
+#elif defined(CONFIG_CMU_BURTCCLK_ULFRCO)
+	CMU_ClockSelectSet(cmuClock_BURTC, cmuSelect_ULFRCO);
+#else
+#error "Unsupported BURTC clock specified"
+#endif
+
+	/* Calculate timing constants and init BURTC */
+	hw_clock_freq = CMU_ClockFreqGet(cmuClock_BURTC);
+	z_clock_hw_cycles_per_sec = hw_clock_freq;
+
+	BUILD_ASSERT(CONFIG_SYS_CLOCK_TICKS_PER_SEC > 0,
+			"Invalid CONFIG_SYS_CLOCK_TICKS_PER_SEC value");
+	g_cyc_per_tick = hw_clock_freq / CONFIG_SYS_CLOCK_TICKS_PER_SEC;
+
+	__ASSERT(g_cyc_per_tick >= MIN_DELAY_CYC,
+		"%u cycle-long tick is too short to be scheduled "
+		"(min is %u). Config: SYS_CLOCK_TICKS_PER_SEC is "
+		"%d and timer frequency is %u",
+		g_cyc_per_tick, MIN_DELAY_CYC, CONFIG_SYS_CLOCK_TICKS_PER_SEC,
+		hw_clock_freq);
+
+	g_max_timeout_ticks = MAX_TIMEOUT_CYC / g_cyc_per_tick;
+
+	init.clkDiv = 1;
+	init.start = false;
+	BURTC_Init(&init);
+
+	/* Enable compare match interrupt */
+	BURTC_IntClear(BURTC_IF_COMP);
+	BURTC_IntEnable(BURTC_IF_COMP);
+	NVIC_ClearPendingIRQ(TIMER_IRQ);
+	IRQ_CONNECT(TIMER_IRQ, DT_INST_IRQ(0, priority), burtc_isr, 0, 0);
+	irq_enable(TIMER_IRQ);
+
+	/* Start the timer and announce 1 kernel tick */
+	atomic_set(&g_last_count, 0);
+	BURTC_CompareSet(0, g_cyc_per_tick);
+
+	BURTC_SyncWait();
+	BURTC->CNT = 0;
+	BURTC_Start();
+
+	return 0;
+}
+
+SYS_INIT(burtc_init, PRE_KERNEL_2,
+	 CONFIG_SYSTEM_CLOCK_INIT_PRIORITY);

dts/arm/silabs/efr32bg22.dtsi

@@ -73,6 +73,10 @@
 	interrupts = <15 0>, <16 0>;
 };
 
+&burtc0 {
+	interrupts = <18 0>;
+};
+
 &stimer0 {
 	interrupts = <12 0>;
 };

dts/arm/silabs/efr32bg27.dtsi

@@ -74,6 +74,10 @@
 	interrupts = <18 0>, <19 0>;
 };
 
+&burtc0 {
+	interrupts = <23 0>;
+};
+
 &stimer0 {
 	interrupts = <15 0>;
 };

dts/arm/silabs/efr32bg2x.dtsi

@@ -17,12 +17,56 @@
 	};
 
 	power-states {
-		standby: standby {
+		/*
+		 * EM1 is a basic "CPU WFI idle", all high-freq clocks remain
+		 * enabled.
+		 */
+		pstate_em1: em1 {
+			compatible = "zephyr,power-state";
+			power-state-name = "runtime-idle";
+			min-residency-us = <4>;
+			/* HFXO remains active */
+			exit-latency-us = <2>;
+		};
+
+		/*
+		 * EM2 is a deepsleep with HF clocks disabled by HW, voltages
+		 * scaled down, etc.
+		 */
+		pstate_em2: em2 {
+			compatible = "zephyr,power-state";
+			power-state-name = "suspend-to-idle";
+			min-residency-us = <260>;
+			exit-latency-us = <250>;
+		};
+
+		/*
+		 * EM3 seems to be exactly the same as EM2 except that
+		 * LFXO & LFRCO should be disabled, so you must use ULFRCO
+		 * as BURTC clock for the system to not lose track of time and
+		 * wake up.
+		 */
+		pstate_em3: em3 {
 			compatible = "zephyr,power-state";
 			power-state-name = "standby";
-			min-residency-us = <50000>;
+			min-residency-us = <20000>;
+			exit-latency-us = <2000>;
+		};
+
+		/*
+		 * EM4 does not preserve CPU or RAM state, so system runs
+		 * through a cold boot upon wake up. BURTC can wake up the
+		 * system from EM4 but that has to be manually configured
+		 * by the application in BURTC registers.
+		 */
+		pstate_em4: em4 {
+			compatible = "zephyr,power-state";
+			power-state-name = "soft-off";
+			min-residency-us = <100000>;
+			exit-latency-us = <80000>;
 		};
 	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -30,7 +74,19 @@
 			device_type = "cpu";
 			compatible = "arm,cortex-m33";
 			reg = <0>;
-			cpu-power-states = <&standby>;
+			/*
+			 * EM1 is enabled by default because it is
+			 * unconditionally safe.
+			 *
+			 * EM2/3 can be enabled by the board code if proper
+			 * timing configuration is ensured:
+			 * - for EM2, EM3: BURTC used as sys_clock
+			 * - for EM3: BURTC clocked from ULFRCO
+			 * Using BURTC as sys_clock instead of SysTick
+			 * has implications on system performance. Read
+			 * KConfig documentation entry before enabling it.
+			 */
+			cpu-power-states = <&pstate_em1>;
 		};
 	};
 
@@ -67,6 +123,12 @@
 			status = "disabled";
 		};
 
+		burtc0: burtc@50064000 {
+			compatible = "silabs,gecko-burtc";
+			reg = <0x50064000 0x3034>;
+			status = "disabled";
+		};
+
 		stimer0: stimer@58000000 {
 			compatible = "silabs,gecko-stimer";
 			reg = <0x58000000 0x3054>;

dts/bindings/timer/silabs,gecko-burtc.yaml

@@ -0,0 +1,15 @@
+# Copyright (c) 2023 Antmicro <www.antmicro.com>
+# SPDX-License-Identifier: Apache-2.0
+
+description: SiLabs Gecko BURTC timer
+
+compatible: "silabs,gecko-burtc"
+
+include: base.yaml
+
+properties:
+  reg:
+    required: true
+
+  interrupts:
+    required: true

soc/arm/silabs_exx32/Kconfig

@@ -21,6 +21,18 @@ config SOC_PART_NUMBER
 	  that you should not set directly. The part number selection choice defines
 	  the default value for this string.
 
+config SOC_GECKO_SERIES2
+	bool
+	help
+	  Set if we're building for Gecko Series 2 SoC.
+	  This is equivalent of _SILICON_LABS_32B_SERIES_2 definition in HAL
+	  code.
+
+config SOC_GECKO_BURTC
+	bool
+	help
+	  Set if the Back-Up Real Time Counter (BURTC) HAL module is used.
+
 config SOC_GECKO_CORE
 	bool
 	default y
@@ -163,6 +175,12 @@ config SOC_GECKO_CMU
 
 if SOC_GECKO_CMU
 
+config CMU_NEED_LFXO
+	bool
+	help
+	  Set if LFXO oscillator should be configured and enabled, potentially
+	  in on-demand mode, after SoC is initialized.
+
 choice
 	prompt "High Frequency Clock Selection"
 	default CMU_HFCLK_HFXO
@@ -175,6 +193,7 @@ config CMU_HFCLK_HFXO
 
 config CMU_HFCLK_LFXO
 	bool "External low frequency crystal oscillator"
+	select CMU_NEED_LFXO
 	help
 	  Set this option to use the external low frequency crystal oscillator
 	  as high frequency clock.
@@ -186,6 +205,37 @@ config CMU_HFCLK_HFRCO
 
 endchoice
 
+
+choice
+	prompt "BURTC Clock Selection"
+	depends on SOC_GECKO_BURTC
+	default CMU_BURTCCLK_LFRCO
+
+config CMU_BURTCCLK_LFXO
+	bool "LFXO - external low frequency crystal oscillator"
+	select CMU_NEED_LFXO
+	help
+	  Set this option to use LFXO - the external low freqency crystal oscillator
+	  as BURTC clock.
+	  Frequency is set by external crystal, typically 32.768 kHz.
+
+config CMU_BURTCCLK_LFRCO
+	bool "LFRCO - internal low frequency RC oscillator"
+	help
+	  Set this option to use LFRCO - the internal low freqency RC oscillator
+	  as BURTC clock.
+	  Frequency is approximately 32.768 kHz.
+
+config CMU_BURTCCLK_ULFRCO
+	bool "ULFRCO - internal ultra low frequency RC oscillator"
+	help
+	  Set this option to use ULFRCO - the external low freqency crystal oscillator
+	  as BURTC clock.
+	  Frequency is approximately 1 kHz.
+
+endchoice
+
+
 config CMU_HFXO_FREQ
 	int "External high frequency oscillator frequency"
 	help

soc/arm/silabs_exx32/Kconfig.defconfig

@@ -9,4 +9,7 @@ config SOC_GECKO_EMU
 	select SOC_GECKO_CORE
 	depends on PM
 
+config CORTEX_M_SYSTICK
+	default n if GECKO_BURTC_TIMER
+
 endif

soc/arm/silabs_exx32/common/soc.c

@@ -41,12 +41,44 @@ LOG_MODULE_REGISTER(soc, CONFIG_SOC_LOG_LEVEL);
  * @brief Initialization parameters for the external high frequency oscillator
  */
 static CMU_HFXOInit_TypeDef hfxoInit = CMU_HFXOINIT_DEFAULT;
-#elif (defined CONFIG_CMU_HFCLK_LFXO)
+#endif
+
+#ifdef CONFIG_CMU_NEED_LFXO
 /**
  * @brief Initialization parameters for the external low frequency oscillator
  */
 static CMU_LFXOInit_TypeDef lfxoInit = CMU_LFXOINIT_DEFAULT;
-#endif
+
+static void init_lfxo(void)
+{
+	/*
+	 * Configuring LFXO disables it, so we can do that only if it's not
+	 * used as a SYSCLK/HFCLK source.
+	 */
+#if defined(_SILICON_LABS_32B_SERIES_2)
+	if (CMU_ClockSelectGet(cmuClock_SYSCLK) != cmuSelect_LFXO) {
+		/*
+		 * Check if device has LFXO configuration info in DEVINFO
+		 * See AN0016.2
+		 */
+		if ((DEVINFO->MODULEINFO & DEVINFO_MODULEINFO_LFXOCALVAL) ==
+		    DEVINFO_MODULEINFO_LFXOCALVAL_VALID) {
+			lfxoInit.capTune =
+				(DEVINFO->MODXOCAL & _DEVINFO_MODXOCAL_LFXOCAPTUNE_MASK) >>
+				_DEVINFO_MODXOCAL_LFXOCAPTUNE_SHIFT;
+		}
+		CMU_LFXOInit(&lfxoInit);
+	}
+#else
+	if (CMU_ClockSelectGet(cmuClock_HF) != cmuSelect_LFXO) {
+		CMU_LFXOInit(&lfxoInit);
+		CMU_OscillatorEnable(cmuOsc_LFXO, true, true);
+	}
+#endif /* _SILICON_LABS_32B_SERIES_2 */
+	SystemLFXOClockSet(CONFIG_CMU_LFXO_FREQ);
+}
+
+#endif /* CONFIG_CMU_NEED_LFXO */
 
 /**
  * @brief Initialize the system clock
@@ -85,29 +117,11 @@ static ALWAYS_INLINE void clock_init(void)
 	CMU_OscillatorEnable(cmuOsc_HFRCO, false, false);
 #endif /* _SILICON_LABS_32B_SERIES_2 */
 #elif (defined CONFIG_CMU_HFCLK_LFXO)
+	/* LFXO should've been already brought up by init_lfxo() */
 #if defined(_SILICON_LABS_32B_SERIES_2)
-	if (CMU_ClockSelectGet(cmuClock_SYSCLK) != cmuSelect_LFXO) {
+	CMU_ClockSelectSet(cmuClock_SYSCLK, cmuSelect_LFXO);
-		/*
-		 * Start the LFXO Oscillator as well (use by RTCC)
-		 * Check if device has HFXO configuration info in DEVINFO
-		 * See AN0016.2
-		 */
-		if ((DEVINFO->MODULEINFO & DEVINFO_MODULEINFO_LFXOCALVAL) ==
-		    DEVINFO_MODULEINFO_LFXOCALVAL_VALID) {
-			lfxoInit.capTune =
-				(DEVINFO->MODXOCAL & _DEVINFO_MODXOCAL_LFXOCAPTUNE_MASK) >>
-				_DEVINFO_MODXOCAL_LFXOCAPTUNE_SHIFT;
-		}
-	}
-
-	SystemLFXOClockSet(CONFIG_CMU_LFXO_FREQ);
 #else
-	if (CMU_ClockSelectGet(cmuClock_HF) != cmuSelect_LFXO) {
+	CMU_ClockSelectSet(cmuClock_HF, cmuSelect_LFXO);
-		CMU_LFXOInit(&lfxoInit);
-		CMU_OscillatorEnable(cmuOsc_LFXO, true, true);
-		CMU_ClockSelectSet(cmuClock_HF, cmuSelect_LFXO);
-	}
-	SystemLFXOClockSet(CONFIG_CMU_LFXO_FREQ);
 	CMU_OscillatorEnable(cmuOsc_HFRCO, false, false);
 #endif /* _SILICON_LABS_32B_SERIES_2 */
 #elif (defined CONFIG_CMU_HFCLK_HFRCO)
@@ -204,6 +218,10 @@ static int silabs_exx32_init(void)
 	/* handle chip errata */
 	CHIP_Init();
 
+#ifdef CONFIG_CMU_NEED_LFXO
+	init_lfxo();
+#endif
+
 #ifdef CONFIG_SOC_GECKO_DEV_INIT
 	sl_device_init_dcdc();
 	sl_device_init_hfxo();
@@ -215,7 +233,7 @@ static int silabs_exx32_init(void)
 	sl_hfxo_manager_init();
 #endif
 
-#else
+#else /* !CONFIG_SOC_GECKO_DEV_INIT */
 
 #ifdef CONFIG_SOC_GECKO_EMU_DCDC
 	dcdc_init();
@@ -234,7 +252,8 @@ static int silabs_exx32_init(void)
 	/* Configure SWO debug output */
 	swo_init();
 #endif
-#endif
+#endif /* !CONFIG_SOC_GECKO_DEV_INIT */
+
 	/* restore interrupt state */
 	irq_unlock(oldLevel);
 	return 0;

soc/arm/silabs_exx32/common/soc_power.c

@@ -9,25 +9,14 @@
 #include <zephyr/pm/pm.h>
 #include <em_emu.h>
 
-#include <zephyr/device.h>
-#include <zephyr/drivers/counter.h>
-
 LOG_MODULE_DECLARE(soc, CONFIG_SOC_LOG_LEVEL);
 
-#ifdef CONFIG_SOC_GECKO_DEV_INIT
-#include <sl_power_manager.h>
-
-static const struct device *const counter_dev = DEVICE_DT_GET(DT_NODELABEL(stimer0));
-static struct counter_alarm_cfg wakeup_cfg = {
-	.callback = NULL
-};
-#endif
-
 /*
  * Power state map:
  * PM_STATE_RUNTIME_IDLE: EM1 Sleep
  * PM_STATE_SUSPEND_TO_IDLE: EM2 Deep Sleep
  * PM_STATE_STANDBY: EM3 Stop
+ * PM_STATE_SOFT_OFF: EM4
  */
 
 /* Invoke Low Power/System Off specific Tasks */
@@ -37,52 +26,6 @@ __weak void pm_state_set(enum pm_state state, uint8_t substate_id)
 
 	LOG_DBG("SoC entering power state %d", state);
 
-#ifdef CONFIG_SOC_GECKO_DEV_INIT
-	sl_power_manager_em_t energy_mode;
-
-	/* Save RTCC IRQ priority */
-	uint32_t rtcc_prio = NVIC_GetPriority(RTCC_IRQn);
-	/*
-	 * When this function is entered the Kernel has disabled handling interrupts
-	 * with priority other than 0. The Interrupt for the timer used to wake up
-	 * the cpu has priority equal to 1. Manually set this priority to 0 so that
-	 * cpu could exit sleep state.
-	 *
-	 * Note on priority value: set priority to -1 because z_arm_irq_priority_set
-	 * offsets the priorities by 1.
-	 * This function call will effectively set the priority to 0.
-	 */
-	z_arm_irq_priority_set(RTCC_IRQn, -1, 0);
-
-	switch (state) {
-
-	case PM_STATE_STANDBY:
-		energy_mode = SL_POWER_MANAGER_EM3;
-
-		/* Limit sleep level to given state */
-		sl_power_manager_add_em_requirement(energy_mode);
-
-		counter_start(counter_dev);
-		counter_set_channel_alarm(counter_dev, 0, &wakeup_cfg);
-		sl_power_manager_sleep();
-		k_cpu_idle();
-		counter_stop(counter_dev);
-
-		/* Remove sleep level limit */
-		sl_power_manager_remove_em_requirement(energy_mode);
-		break;
-
-	default:
-		LOG_DBG("Unsupported power state %u", state);
-		break;
-	}
-
-	LOG_DBG("SoC leaving power state %d", state);
-
-	/* Restore RTCC IRQ priority */
-	z_arm_irq_priority_set(RTCC_IRQn, (rtcc_prio - 1), 0);
-#else
-
 	/* FIXME: When this function is entered the Kernel has disabled
 	 * interrupts using BASEPRI register. This is incorrect as it prevents
 	 * waking up from any interrupt which priority is not 0. Work around the
@@ -105,6 +48,9 @@ __weak void pm_state_set(enum pm_state state, uint8_t substate_id)
 	case PM_STATE_STANDBY:
 		EMU_EnterEM3(true);
 		break;
+	case PM_STATE_SOFT_OFF:
+		EMU_EnterEM4();
+		break;
 	default:
 		LOG_DBG("Unsupported power state %u", state);
 		break;
@@ -114,8 +60,6 @@ __weak void pm_state_set(enum pm_state state, uint8_t substate_id)
 
 	/* Clear PRIMASK */
 	__enable_irq();
-
-#endif
 }
 
 /* Handle SOC specific activity after Low Power Mode Exit */
@@ -124,37 +68,3 @@ __weak void pm_state_exit_post_ops(enum pm_state state, uint8_t substate_id)
 	ARG_UNUSED(state);
 	ARG_UNUSED(substate_id);
 }
-
-#if defined(CONFIG_SOC_GECKO_DEV_INIT) && defined(CONFIG_PM_POLICY_CUSTOM)
-/* CONFIG_PM_POLICY_CUSTOM allows us to set the next alarm to a specific number
- * of ticks in the future. This is needed for the Gecko SleepTimer to wake up
- * the device properly.
- */
-static const struct pm_state_info pm_min_residency[] =
-	PM_STATE_INFO_LIST_FROM_DT_CPU(DT_NODELABEL(cpu0));
-struct pm_state_info pm_state_active = {PM_STATE_ACTIVE, 0, 0, 0};
-
-__weak struct pm_state_info *pm_policy_next_state(uint8_t cpu, int32_t ticks)
-{
-	int i;
-
-	for (i = ARRAY_SIZE(pm_min_residency) - 1; i >= 0; i--) {
-
-		if ((ticks == K_TICKS_FOREVER) ||
-		    (ticks >= k_us_to_ticks_ceil32(
-			     pm_min_residency[i].min_residency_us))) {
-			LOG_DBG("Selected power state %d "
-				"(ticks: %d, min_residency: %u)",
-				pm_min_residency[i].state, ticks,
-				pm_min_residency[i].min_residency_us);
-
-			/* Busy waiting for 1 tick to flush UART buffer */
-			k_busy_wait(k_ticks_to_us_floor32(1));
-			wakeup_cfg.ticks = ticks;
-
-			return ((struct pm_state_info *) &pm_min_residency[i]);
-		}
-	}
-	return (struct pm_state_info *)(&pm_state_active);
-}
-#endif

soc/arm/silabs_exx32/efr32bg22/Kconfig.defconfig.series

@@ -19,11 +19,6 @@ config PM
 	select COUNTER
 	select UART_INTERRUPT_DRIVEN
 
-choice PM_POLICY
-	default PM_POLICY_CUSTOM
-	depends on PM
-endchoice
-
 source "soc/arm/silabs_exx32/efr32bg22/Kconfig.defconfig.efr32bg22"
 
 endif # SOC_SERIES_EFR32BG22

soc/arm/silabs_exx32/efr32bg22/Kconfig.series

@@ -15,6 +15,7 @@ config SOC_SERIES_EFR32BG22
 	select HAS_SILABS_GECKO
 	select HAS_SWO
 	select SOC_FAMILY_EXX32
+	select SOC_GECKO_SERIES2
 	select SOC_GECKO_CMU
 	select SOC_GECKO_CORE
 	select SOC_GECKO_DEV_INIT

soc/arm/silabs_exx32/efr32bg27/Kconfig.series

@@ -15,6 +15,7 @@ config SOC_SERIES_EFR32BG27
 	select HAS_SILABS_GECKO
 	select HAS_SWO
 	select SOC_FAMILY_EXX32
+	select SOC_GECKO_SERIES2
 	select SOC_GECKO_CMU
 	select SOC_GECKO_CORE
 	select SOC_GECKO_DEV_INIT

soc/arm/silabs_exx32/efr32mg21/Kconfig.series

@@ -12,6 +12,7 @@ config SOC_SERIES_EFR32MG21
 	select CPU_HAS_FPU
 	select CPU_HAS_ARM_MPU
 	select SOC_FAMILY_EXX32
+	select SOC_GECKO_SERIES2
 	select HAS_SILABS_GECKO
 	select HAS_SWO
 	select SOC_GECKO_CMU

soc/arm/silabs_exx32/efr32mg24/Kconfig.series

@@ -14,6 +14,7 @@ config SOC_SERIES_EFR32MG24
 	select ARMV8_M_DSP
 	select ARM_TRUSTZONE_M
 	select SOC_FAMILY_EXX32
+	select SOC_GECKO_SERIES2
 	select HAS_SILABS_GECKO
 	select HAS_SWO
 	select SOC_GECKO_CMU