soc: stm32: PM: Disable jtag port pins if no debug

At chip startup, jtag pins are configured by default to enable
debug.
This configuration adds consumption and when using PM profile,
we can save ~40uA by resetting this configuration and setting pins
to analog mode.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>

dts/arm/st/wba/stm32wba.dtsi

@@ -98,6 +98,12 @@
 		};
 	};
 
+	jtag_port: jtag_port {
+		compatible = "gpio-jtag";
+		jtag-gpios = <&gpioa 13 0>, <&gpioa 14 0>, <&gpioa 15 0>,
+			     <&gpiob 3 0> ,<&gpiob 4 0>;
+	};
+
 	soc {
 		flash: flash-controller@40022000 {
 			compatible = "st,stm32-flash-controller", "st,stm32wba-flash-controller";

dts/bindings/gpio/swj-connector.yaml

@@ -0,0 +1,5 @@
+description: Serial Wire - JTAG Connector
+
+compatible: "swj-connector"
+
+include: pinctrl-device.yaml

soc/arm/st_stm32/common/CMakeLists.txt

@@ -8,3 +8,7 @@ zephyr_sources_ifdef(CONFIG_STM32_BACKUP_SRAM stm32_backup_sram.c)
 zephyr_linker_sources_ifdef(CONFIG_STM32_BACKUP_SRAM SECTIONS stm32_backup_sram.ld)
 
 zephyr_sources(soc_config.c)
+
+if (NOT CONFIG_DEBUG AND CONFIG_PM)
+  zephyr_sources_ifdef(CONFIG_DT_HAS_SWJ_CONNECTOR_ENABLED pm_debug_swj.c)
+endif()

soc/arm/st_stm32/common/pm_debug_swj.c

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2023 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/drivers/pinctrl.h>
+#include <zephyr/init.h>
+
+#define SWJ_NODE DT_NODELABEL(swj_port)
+
+PINCTRL_DT_DEFINE(SWJ_NODE);
+
+const struct pinctrl_dev_config *swj_pcfg = PINCTRL_DT_DEV_CONFIG_GET(SWJ_NODE);
+
+/*
+ * Serial Wire / JTAG port pins are enabled as part of SoC default configuration.
+ * When debug access is not needed and in case power consumption performance is
+ * expected, configure matching pins to analog in order to save power.
+ */
+
+static int swj_to_analog(void)
+{
+	int err;
+
+	/* Set Serial Wire / JTAG port pins to analog mode */
+	err = pinctrl_apply_state(swj_pcfg, PINCTRL_STATE_SLEEP);
+	if (err < 0) {
+		__ASSERT(0, "SWJ pinctrl setup failed");
+		return err;
+	}
+
+	return 0;
+}
+
+SYS_INIT(swj_to_analog, POST_KERNEL, CONFIG_KERNEL_INIT_PRIORITY_DEVICE);