src/drivers/uart/uart8250io.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <arch/io.h>
   4 #include <boot/coreboot_tables.h>
   5 #include <commonlib/bsd/helpers.h>
   6 #include <console/uart.h>
   7 #include <stdint.h>
   8
   9 #include "uart8250reg.h"
  10
  11 /* Should support 8250, 16450, 16550, 16550A type UARTs */
  12
  13 /* Expected character delay at 1200bps is 9ms for a working UART
  14  * and no flow-control. Assume UART as stuck if shift register
  15  * or FIFO takes more than 50ms per character to appear empty.
  16  *
  17  * Estimated that inb() from UART takes 1 microsecond.
  18  */
  19 #define SINGLE_CHAR_TIMEOUT     (50 * 1000)
  20 #define FIFO_TIMEOUT            (16 * SINGLE_CHAR_TIMEOUT)
  21
  22 static int uart8250_can_tx_byte(unsigned int base_port)
  23 {
  24         return inb(base_port + UART8250_LSR) & UART8250_LSR_THRE;
  25 }
  26
  27 static void uart8250_tx_byte(unsigned int base_port, unsigned char data)
  28 {
  29         unsigned long int i = SINGLE_CHAR_TIMEOUT;
  30         while (i-- && !uart8250_can_tx_byte(base_port));
  31         outb(data, base_port + UART8250_TBR);
  32 }
  33
  34 static void uart8250_tx_flush(unsigned int base_port)
  35 {
  36         unsigned long int i = FIFO_TIMEOUT;
  37         while (i-- && !(inb(base_port + UART8250_LSR) & UART8250_LSR_TEMT));
  38 }
  39
  40 static int uart8250_can_rx_byte(unsigned int base_port)
  41 {
  42         return inb(base_port + UART8250_LSR) & UART8250_LSR_DR;
  43 }
  44
  45 static unsigned char uart8250_rx_byte(unsigned int base_port)
  46 {
  47         unsigned long int i = SINGLE_CHAR_TIMEOUT;
  48         while (i && !uart8250_can_rx_byte(base_port))
  49                 i--;
  50
  51         if (i)
  52                 return inb(base_port + UART8250_RBR);
  53         else
  54                 return 0x0;
  55 }
  56
  57 static void uart8250_init(unsigned int base_port, unsigned int divisor)
  58 {
  59         /* Disable interrupts */
  60         outb(0x0, base_port + UART8250_IER);
  61         /* Enable FIFOs */
  62         outb(UART8250_FCR_FIFO_EN, base_port + UART8250_FCR);
  63
  64         /* assert DTR and RTS so the other end is happy */
  65         outb(UART8250_MCR_DTR | UART8250_MCR_RTS, base_port + UART8250_MCR);
  66
  67         /* DLAB on */
  68         outb(UART8250_LCR_DLAB | CONFIG_TTYS0_LCS, base_port + UART8250_LCR);
  69
  70         /* Set Baud Rate Divisor. 12 ==> 9600 Baud */
  71         outb(divisor & 0xFF,   base_port + UART8250_DLL);
  72         outb((divisor >> 8) & 0xFF,    base_port + UART8250_DLM);
  73
  74         /* Set to 3 for 8N1 */
  75         outb(CONFIG_TTYS0_LCS, base_port + UART8250_LCR);
  76 }
  77
  78 static const unsigned int bases[] = { 0x3f8, 0x2f8, 0x3e8, 0x2e8 };
  79
  80 uintptr_t uart_platform_base(unsigned int idx)
  81 {
  82         if (idx < ARRAY_SIZE(bases))
  83                 return bases[idx];
  84         return 0;
  85 }
  86
  87 void uart_init(unsigned int idx)
  88 {
  89         if (!CONFIG(DRIVERS_UART_8250IO_SKIP_INIT)) {
  90                 unsigned int div;
  91                 div = uart_baudrate_divisor(get_uart_baudrate(),
  92                         uart_platform_refclk(), uart_input_clock_divider());
  93                 uart8250_init(uart_platform_base(idx), div);
  94         }
  95 }
  96
  97 void uart_tx_byte(unsigned int idx, unsigned char data)
  98 {
  99         uart8250_tx_byte(uart_platform_base(idx), data);
 100 }
 101
 102 unsigned char uart_rx_byte(unsigned int idx)
 103 {
 104         return uart8250_rx_byte(uart_platform_base(idx));
 105 }
 106
 107 void uart_tx_flush(unsigned int idx)
 108 {
 109         uart8250_tx_flush(uart_platform_base(idx));
 110 }
 111
 112 enum cb_err fill_lb_serial(struct lb_serial *serial)
 113 {
 114         serial->type = LB_SERIAL_TYPE_IO_MAPPED;
 115         serial->baseaddr = uart_platform_base(CONFIG_UART_FOR_CONSOLE);
 116         serial->baud = get_uart_baudrate();
 117         serial->regwidth = 1;
 118         serial->input_hertz = uart_platform_refclk();
 119
 120         return CB_SUCCESS;
 121 }