esp32s2: drivers: serial: add minimal uart driver

based on uart rom functions, also enable console driver
on top of this driver, which enables logging

Signed-off-by: Glauber Maroto Ferreira <glauber.ferreira@espressif.com>

CODEOWNERS

@@ -318,6 +318,7 @@
 /drivers/serial/Kconfig.test              @str4t0m
 /drivers/serial/serial_test.c             @str4t0m
 /drivers/serial/*esp32c3*                 @uLipe
+/drivers/serial/*esp32s2*                 @glaubermaroto
 /drivers/disk/                            @jfischer-no
 /drivers/disk/sdmmc_sdhc.h                @JunYangNXP
 /drivers/disk/sdmmc_spi.c                 @JunYangNXP

boards/xtensa/esp32s2_saola/esp32s2_saola.dts

@@ -14,5 +14,12 @@
 
 	chosen {
 		zephyr,sram = &sram0;
+		zephyr,console = &uart0;
+		zephyr,shell-uart = &uart0;
 	};
 };
+
+&uart0 {
+	status = "okay";
+	current-speed = <115200>;
+};

boards/xtensa/esp32s2_saola/esp32s2_saola_defconfig

@@ -8,6 +8,11 @@ CONFIG_MAIN_STACK_SIZE=2048
 
 CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC=240000000
 
+CONFIG_CONSOLE=y
+CONFIG_SERIAL=y
+CONFIG_UART_CONSOLE=y
+CONFIG_UART_ROM_ESP32S2=y
+
 CONFIG_XTENSA_USE_CORE_CRT1=n
 
 CONFIG_GEN_ISR_TABLES=y

drivers/serial/CMakeLists.txt

@@ -9,6 +9,7 @@ zephyr_library_sources_ifdef(CONFIG_UART_CC32XX uart_cc32xx.c)
 zephyr_library_sources_ifdef(CONFIG_UART_CMSDK_APB uart_cmsdk_apb.c)
 zephyr_library_sources_ifdef(CONFIG_UART_ESP32 uart_esp32.c)
 zephyr_library_sources_ifdef(CONFIG_UART_ROM_ESP32C3 uart_rom_esp32c3.c)
+zephyr_library_sources_ifdef(CONFIG_UART_ROM_ESP32S2 uart_rom_esp32s2.c)
 zephyr_library_sources_ifdef(CONFIG_UART_SIFIVE uart_sifive.c)
 zephyr_library_sources_ifdef(CONFIG_UART_GECKO uart_gecko.c)
 zephyr_library_sources_ifdef(CONFIG_LEUART_GECKO leuart_gecko.c)

drivers/serial/Kconfig

@@ -123,6 +123,8 @@ source "drivers/serial/Kconfig.esp32"
 
 source "drivers/serial/Kconfig.esp32c3_rom"
 
+source "drivers/serial/Kconfig.esp32s2_rom"
+
 source "drivers/serial/Kconfig.gecko"
 
 source "drivers/serial/Kconfig.leuart_gecko"

drivers/serial/Kconfig.esp32s2_rom

@@ -0,0 +1,10 @@
+# Copyright (c) 2021 Espressif Systems (Shanghai) Co., Ltd.
+# SPDX-License-Identifier: Apache-2.0
+
+config UART_ROM_ESP32S2
+	bool "ESP32S2 ROM UART driver"
+	default y
+	select SERIAL_HAS_DRIVER
+	depends on SOC_ESP32S2
+	help
+	  Enable the ESP32S2 UART using ROM routines.

drivers/serial/uart_rom_esp32s2.c

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2021 Espressif Systems (Shanghai) Co., Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT espressif_esp32s2_uart
+
+/* Include esp-idf headers first to avoid redefining BIT() macro */
+#include <soc.h>
+#include <esp_attr.h>
+#include <device.h>
+#include <drivers/uart.h>
+#include <drivers/clock_control.h>
+
+static int uart_rom_esp32s2_poll_in(const struct device *dev, unsigned char *p_char)
+{
+	ARG_UNUSED(dev);
+	return (int)esp_rom_uart_rx_one_char(p_char);
+}
+
+static IRAM_ATTR void uart_rom_esp32s2_poll_out(const struct device *dev,
+				unsigned char c)
+{
+	ARG_UNUSED(dev);
+	esp_rom_uart_tx_one_char(c);
+}
+
+static int uart_rom_esp32s2_poll_err_check(const struct device *dev)
+{
+	ARG_UNUSED(dev);
+	return 0;
+}
+
+static int uart_rom_esp32s2_init(const struct device *dev)
+{
+	ARG_UNUSED(dev);
+	return 0;
+}
+
+static const DRAM_ATTR struct uart_driver_api uart_rom_esp32s2_api = {
+	.poll_in = uart_rom_esp32s2_poll_in,
+	.poll_out = uart_rom_esp32s2_poll_out,
+	.err_check = uart_rom_esp32s2_poll_err_check,
+};
+
+#define ESP32S2_ROM_UART_INIT(idx)	\
+DEVICE_DT_DEFINE(DT_NODELABEL(uart##idx),	\
+		    &uart_rom_esp32s2_init,	\
+		    NULL,	\
+		    NULL,	\
+		    NULL,	\
+		    PRE_KERNEL_1,	\
+		    CONFIG_KERNEL_INIT_PRIORITY_DEVICE,	\
+		    &uart_rom_esp32s2_api);	\
+
+DT_INST_FOREACH_STATUS_OKAY(ESP32S2_ROM_UART_INIT)

dts/bindings/serial/espressif,esp32s2-uart.yaml

@@ -0,0 +1,32 @@
+description: ESP32S2 UART
+
+compatible: "espressif,esp32s2-uart"
+
+include: uart-controller.yaml
+
+properties:
+    reg:
+      required: true
+
+    interrupts:
+      required: false
+
+    tx-pin:
+      type: int
+      description: TX pin
+      required: false
+
+    rx-pin:
+      type: int
+      description: RX pin
+      required: false
+
+    rts-pin:
+      type: int
+      description: RTS pin
+      required: false
+
+    cts-pin:
+      type: int
+      description: CTS pin
+      required: false

dts/xtensa/espressif/esp32s2.dtsi

@@ -30,6 +30,13 @@
 			compatible = "mmio-sram";
 			reg = <0x3ffb0000 0x50000>;
 		};
+
+		uart0: uart@3f400000 {
+			compatible = "espressif,esp32s2-uart";
+			reg = <0x3f400000 0x400>;
+			label = "UART_0";
+			status = "disabled";
+		};
 	};
 
 };