board: nuvoton: update console environment variable

If CONFIG_SYS_SKIP_UART_INIT is enabled, calculate the
current baud rate and update the "console" environment
variable.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>

board/nuvoton/arbel_evb/Kconfig

@@ -15,4 +15,5 @@ config SYS_MEM_TOP_HIDE
 	help
 	  Reserve memory for ECC/GFX/OPTEE/TIP/CP.
 
+source "board/nuvoton/common/Kconfig"
 endif

board/nuvoton/arbel_evb/arbel_evb.c

@@ -7,6 +7,7 @@
 #include <dm.h>
 #include <asm/io.h>
 #include <asm/arch/gcr.h>
+#include "../common/uart.h"
 
 #define SR_MII_CTRL_SWR_BIT15	15
 
@@ -90,3 +91,9 @@ int dram_init_banksize(void)
 	return 0;
 }
 
+int last_stage_init(void)
+{
+	board_set_console();
+
+	return 0;
+}

board/nuvoton/common/Kconfig

@@ -0,0 +1,9 @@
+if ARCH_NPCM
+
+config SYS_SKIP_UART_INIT
+	bool "Skip UART initialization"
+	depends on NPCM_SERIAL
+	help
+	  Select this if the UART you want to use is already
+	  initialized by the time U-Boot starts its execution.
+endif

board/nuvoton/common/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_SYS_SKIP_UART_INIT)	+= uart.o

board/nuvoton/common/uart.c

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2023 Nuvoton Technology Corp.
+ */
+
+#include <clk.h>
+#include <dm.h>
+#include <env.h>
+#include <serial.h>
+#include <linux/delay.h>
+
+#define UART_DLL	0x0
+#define UART_DLM	0x4
+#define UART_LCR	0xc
+#define LCR_DLAB	BIT(7)
+
+void board_set_console(void)
+{
+	const unsigned long baudrate_table[] = CFG_SYS_BAUDRATE_TABLE;
+	struct udevice *dev = gd->cur_serial_dev;
+	unsigned int baudrate, max_delta;
+	void __iomem *uart_reg;
+	struct clk clk;
+	char string[32];
+	u32 uart_clk;
+	u8 dll, dlm;
+	u16 divisor;
+	int ret, i;
+
+	if (!dev)
+		return;
+
+	uart_reg = dev_read_addr_ptr(dev);
+	ret = clk_get_by_index(dev, 0, &clk);
+	if (ret)
+		return;
+
+	uart_clk = clk_get_rate(&clk);
+	setbits_8(uart_reg + UART_LCR, LCR_DLAB);
+	dll = readb(uart_reg + UART_DLL);
+	dlm = readb(uart_reg + UART_DLM);
+	clrbits_8(uart_reg + UART_LCR, LCR_DLAB);
+	divisor = dll | (dlm << 8);
+	baudrate =  uart_clk / ((16 * (divisor + 2)));
+	for (i = 0; i < ARRAY_SIZE(baudrate_table); ++i) {
+		max_delta = baudrate_table[i] / 20;
+		if (abs(baudrate - baudrate_table[i]) < max_delta) {
+			/* The baudrate is supported */
+			gd->baudrate = baudrate_table[i];
+			break;
+		}
+	}
+
+	if (i == ARRAY_SIZE(baudrate_table)) {
+		/* current baudrate is not suitable, set to default */
+		divisor = DIV_ROUND_CLOSEST(uart_clk, 16 * gd->baudrate) - 2;
+		setbits_8(uart_reg + UART_LCR, LCR_DLAB);
+		writeb(divisor & 0xff, uart_reg + UART_DLL);
+		writeb(divisor >> 8, uart_reg + UART_DLM);
+		clrbits_8(uart_reg + UART_LCR, LCR_DLAB);
+		udelay(100);
+		printf("\r\nUART(source %u): change baudrate from %u to %u\n",
+		       uart_clk, baudrate, uart_clk / ((16 * (divisor + 2))));
+	}
+
+	debug("Set env baudrate=%u\n", gd->baudrate);
+	snprintf(string, sizeof(string), "ttyS0,%un8", gd->baudrate);
+	env_set("console", string);
+
+}

board/nuvoton/common/uart.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2023 Nuvoton Technology Corp.
+ */
+
+#ifndef _NUVOTON_UART_H
+#define _NUVOTON_UART_H
+
+void board_set_console(void);
+
+#endif /* _NUVOTON_COMMON_H */

board/nuvoton/poleg_evb/Kconfig

@@ -22,4 +22,5 @@ config TARGET_POLEG_EVB
 
 endchoice
 
+source "board/nuvoton/common/Kconfig"
 endif

board/nuvoton/poleg_evb/poleg_evb.c

@@ -10,6 +10,7 @@
 #include <asm/io.h>
 #include <asm/arch/gcr.h>
 #include <asm/mach-types.h>
+#include "../common/uart.h"
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -53,3 +54,10 @@ int dram_init(void)
 
 	return 0;
 }
+
+int last_stage_init(void)
+{
+	board_set_console();
+
+	return 0;
+}