soc: silabs: add a config for low latency interrupt on Sliabs S2 devices

The high frequency clock was always restored before handling the
interrupts to make sure that the system clock is as expected. However,
the response time to interrupt when we were in EM2 was a between 300 and
600 us. By default, we use the low interrupt latency.

Signed-off-by: Bastien Beauchamp <[email protected]>

Author: silabs-BastienB

soc/silabs/Kconfig

@@ -153,6 +153,13 @@ config SOC_GECKO_PM_BACKEND_EMU
 	help
 	  Implement PM using direct calls to EMU driver in emlib
 
+config SOC_SILABS_PM_LOW_INTERRUPT_LATENCY
+	bool "Low interrupt latency mode"
+	default y if SOC_GECKO_PM_BACKEND_PMGR
+	help
+	  Enabling low interrupt latency allows interrupts to be executed
+	  before the high frequency clock is restored after sleep.
+
 endif # PM
 
 config SOC_GECKO_EMU_DCDC

soc/silabs/common/soc_power_pmgr.c

@@ -87,6 +87,7 @@ bool sl_power_manager_is_ok_to_sleep(void)
 	return true;
 }
 
+#if !defined(CONFIG_SOC_SILABS_PM_LOW_INTERRUPT_LATENCY)
 /* This function is called by sl_power_manager_sleep() right after it was woken up from WFI. */
 void sli_power_manager_on_wakeup(void)
 {
@@ -98,6 +99,7 @@ void sli_power_manager_on_wakeup(void)
 	sl_power_manager_add_em_requirement(SL_POWER_MANAGER_EM1);
 	sl_power_manager_remove_em_requirement(SL_POWER_MANAGER_EM1);
 }
+#endif
 
 /**
  * Some SiLabs blobs, such as RAIL, call directly into sl_power_manager, and