drivers: flash: silabs: Add low power write support

Add low-power-write property to MSC device tree node, set
MSC_WRITECTRL_LPWRITE if enabled.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>

drivers/flash/soc_flash_silabs_series2.c

@@ -32,6 +32,7 @@ struct flash_silabs_data {
 struct flash_silabs_config {
 	struct flash_parameters flash_parameters;
 	struct flash_pages_layout page_layout;
+	bool lpwrite;
 };
 
 static bool flash_silabs_read_range_is_valid(off_t offset, uint32_t size)
@@ -191,9 +192,14 @@ static int flash_silabs_get_size(const struct device *dev, uint64_t *size)
 static int flash_silabs_init(const struct device *dev)
 {
 	struct flash_silabs_data *const dev_data = dev->data;
+	const struct flash_silabs_config *config = dev->config;
 
 	MSC_Init();
 
+	if (config->lpwrite) {
+		MSC->WRITECTRL_SET = MSC_WRITECTRL_LPWRITE;
+	}
+
 	/* Lock the MSC module. */
 	flash_silabs_write_protection(true);
 
@@ -236,6 +242,7 @@ static const struct flash_silabs_config flash_silabs_config_0 = {
 				DT_PROP(SOC_NV_FLASH_NODE, erase_block_size),
 		.pages_size = DT_PROP(SOC_NV_FLASH_NODE, erase_block_size),
 	},
+	.lpwrite = DT_INST_PROP(0, low_power_write),
 };
 /* clang-format on */
 

dts/bindings/flash_controller/silabs,series2-flash-controller.yaml

@@ -6,3 +6,9 @@ description: Silicon Labs Series 2 flash controller
 compatible: "silabs,series2-flash-controller"
 
 include: flash-controller.yaml
+
+properties:
+  low-power-write:
+    type: boolean
+    description: |
+      Reduce current consumption during write, doubling write time

tests/drivers/flash/common/boards/xg24_rb4187c_lpwrite.overlay

@@ -0,0 +1,13 @@
+/*
+ * Copyright (c) 2025 Silicon Laboratories Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&dma0 {
+	status = "okay";
+};
+
+&msc {
+	dmas = <&dma0 DMA_REQSEL_MSCWDATA>;
+	low-power-write;
+};

tests/drivers/flash/common/testcase.yaml

@@ -99,3 +99,10 @@ tests:
       - xg24_rb4187c
     extra_configs:
       - CONFIG_DMA=y
+  drivers.flash.common.silabs.dma.lpwrite:
+    platform_allow:
+      - xg24_rb4187c
+    extra_configs:
+      - CONFIG_DMA=y
+    extra_args:
+      - DTC_OVERLAY_FILE=boards/xg24_rb4187c_lpwrite.overlay