board/nuvoton/common/uart.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (c) 2023 Nuvoton Technology Corp.
   4  */
   5
   6 #include <clk.h>
   7 #include <dm.h>
   8 #include <env.h>
   9 #include <serial.h>
  10 #include <linux/delay.h>
  11
  12 #define UART_DLL        0x0
  13 #define UART_DLM        0x4
  14 #define UART_LCR        0xc
  15 #define LCR_DLAB        BIT(7)
  16
  17 void board_set_console(void)
  18 {
  19         const unsigned long baudrate_table[] = CFG_SYS_BAUDRATE_TABLE;
  20         struct udevice *dev = gd->cur_serial_dev;
  21         unsigned int baudrate, max_delta;
  22         void __iomem *uart_reg;
  23         struct clk clk;
  24         char string[32];
  25         u32 uart_clk;
  26         u8 dll, dlm;
  27         u16 divisor;
  28         int ret, i;
  29
  30         if (!dev)
  31                 return;
  32
  33         uart_reg = dev_read_addr_ptr(dev);
  34         ret = clk_get_by_index(dev, 0, &clk);
  35         if (ret)
  36                 return;
  37
  38         uart_clk = clk_get_rate(&clk);
  39         setbits_8(uart_reg + UART_LCR, LCR_DLAB);
  40         dll = readb(uart_reg + UART_DLL);
  41         dlm = readb(uart_reg + UART_DLM);
  42         clrbits_8(uart_reg + UART_LCR, LCR_DLAB);
  43         divisor = dll | (dlm << 8);
  44         baudrate =  uart_clk / ((16 * (divisor + 2)));
  45         for (i = 0; i < ARRAY_SIZE(baudrate_table); ++i) {
  46                 max_delta = baudrate_table[i] / 20;
  47                 if (abs(baudrate - baudrate_table[i]) < max_delta) {
  48                         /* The baudrate is supported */
  49                         gd->baudrate = baudrate_table[i];
  50                         break;
  51                 }
  52         }
  53
  54         if (i == ARRAY_SIZE(baudrate_table)) {
  55                 /* current baudrate is not suitable, set to default */
  56                 divisor = DIV_ROUND_CLOSEST(uart_clk, 16 * gd->baudrate) - 2;
  57                 setbits_8(uart_reg + UART_LCR, LCR_DLAB);
  58                 writeb(divisor & 0xff, uart_reg + UART_DLL);
  59                 writeb(divisor >> 8, uart_reg + UART_DLM);
  60                 clrbits_8(uart_reg + UART_LCR, LCR_DLAB);
  61                 udelay(100);
  62                 printf("\r\nUART(source %u): change baudrate from %u to %u\n",
  63                        uart_clk, baudrate, uart_clk / ((16 * (divisor + 2))));
  64         }
  65
  66         debug("Set env baudrate=%u\n", gd->baudrate);
  67         snprintf(string, sizeof(string), "ttyS0,%un8", gd->baudrate);
  68         env_set("console", string);
  69
  70 }