drivers/tty/serial/8250/8250_early.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Early serial console for 8250/16550 devices
   4  *
   5  * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
   6  *      Bjorn Helgaas <bjorn.helgaas@hp.com>
   7  *
   8  * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
   9  * and on early_printk.c by Andi Kleen.
  10  *
  11  * This is for use before the serial driver has initialized, in
  12  * particular, before the UARTs have been discovered and named.
  13  * Instead of specifying the console device as, e.g., "ttyS0",
  14  * we locate the device directly by its MMIO or I/O port address.
  15  *
  16  * The user can specify the device directly, e.g.,
  17  *      earlycon=uart8250,io,0x3f8,9600n8
  18  *      earlycon=uart8250,mmio,0xff5e0000,115200n8
  19  *      earlycon=uart8250,mmio32,0xff5e0000,115200n8
  20  * or
  21  *      console=uart8250,io,0x3f8,9600n8
  22  *      console=uart8250,mmio,0xff5e0000,115200n8
  23  *      console=uart8250,mmio32,0xff5e0000,115200n8
  24  */
  25
  26 #include <linux/tty.h>
  27 #include <linux/init.h>
  28 #include <linux/console.h>
  29 #include <linux/of.h>
  30 #include <linux/of_device.h>
  31 #include <linux/serial_reg.h>
  32 #include <linux/serial.h>
  33 #include <linux/serial_8250.h>
  34 #include <asm/io.h>
  35 #include <asm/serial.h>
  36
  37 static unsigned int serial8250_early_in(struct uart_port *port, int offset)
  38 {
  39         int reg_offset = offset;
  40         offset <<= port->regshift;
  41
  42         switch (port->iotype) {
  43         case UPIO_MEM:
  44                 return readb(port->membase + offset);
  45         case UPIO_MEM16:
  46                 return readw(port->membase + offset);
  47         case UPIO_MEM32:
  48                 return readl(port->membase + offset);
  49         case UPIO_MEM32BE:
  50                 return ioread32be(port->membase + offset);
  51         case UPIO_PORT:
  52                 return inb(port->iobase + offset);
  53         case UPIO_AU:
  54                 return port->serial_in(port, reg_offset);
  55         default:
  56                 return 0;
  57         }
  58 }
  59
  60 static void serial8250_early_out(struct uart_port *port, int offset, int value)
  61 {
  62         int reg_offset = offset;
  63         offset <<= port->regshift;
  64
  65         switch (port->iotype) {
  66         case UPIO_MEM:
  67                 writeb(value, port->membase + offset);
  68                 break;
  69         case UPIO_MEM16:
  70                 writew(value, port->membase + offset);
  71                 break;
  72         case UPIO_MEM32:
  73                 writel(value, port->membase + offset);
  74                 break;
  75         case UPIO_MEM32BE:
  76                 iowrite32be(value, port->membase + offset);
  77                 break;
  78         case UPIO_PORT:
  79                 outb(value, port->iobase + offset);
  80                 break;
  81         case UPIO_AU:
  82                 port->serial_out(port, reg_offset, value);
  83                 break;
  84         }
  85 }
  86
  87 static void serial_putc(struct uart_port *port, unsigned char c)
  88 {
  89         unsigned int status;
  90
  91         serial8250_early_out(port, UART_TX, c);
  92
  93         for (;;) {
  94                 status = serial8250_early_in(port, UART_LSR);
  95                 if (uart_lsr_tx_empty(status))
  96                         break;
  97                 cpu_relax();
  98         }
  99 }
 100
 101 static void early_serial8250_write(struct console *console,
 102                                         const char *s, unsigned int count)
 103 {
 104         struct earlycon_device *device = console->data;
 105         struct uart_port *port = &device->port;
 106
 107         uart_console_write(port, s, count, serial_putc);
 108 }
 109
 110 #ifdef CONFIG_CONSOLE_POLL
 111 static int early_serial8250_read(struct console *console,
 112                                  char *s, unsigned int count)
 113 {
 114         struct earlycon_device *device = console->data;
 115         struct uart_port *port = &device->port;
 116         unsigned int status;
 117         int num_read = 0;
 118
 119         while (num_read < count) {
 120                 status = serial8250_early_in(port, UART_LSR);
 121                 if (!(status & UART_LSR_DR))
 122                         break;
 123                 s[num_read++] = serial8250_early_in(port, UART_RX);
 124         }
 125
 126         return num_read;
 127 }
 128 #else
 129 #define early_serial8250_read NULL
 130 #endif
 131
 132 static void __init init_port(struct earlycon_device *device)
 133 {
 134         struct uart_port *port = &device->port;
 135         unsigned int divisor;
 136         unsigned char c;
 137         unsigned int ier;
 138
 139         serial8250_early_out(port, UART_LCR, 0x3);      /* 8n1 */
 140         ier = serial8250_early_in(port, UART_IER);
 141         serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); /* no interrupt */
 142         serial8250_early_out(port, UART_FCR, 0);        /* no fifo */
 143         serial8250_early_out(port, UART_MCR, 0x3);      /* DTR + RTS */
 144
 145         if (port->uartclk) {
 146                 divisor = DIV_ROUND_CLOSEST(port->uartclk, 16 * device->baud);
 147                 c = serial8250_early_in(port, UART_LCR);
 148                 serial8250_early_out(port, UART_LCR, c | UART_LCR_DLAB);
 149                 serial8250_early_out(port, UART_DLL, divisor & 0xff);
 150                 serial8250_early_out(port, UART_DLM, (divisor >> 8) & 0xff);
 151                 serial8250_early_out(port, UART_LCR, c & ~UART_LCR_DLAB);
 152         }
 153 }
 154
 155 int __init early_serial8250_setup(struct earlycon_device *device,
 156                                          const char *options)
 157 {
 158         if (!(device->port.membase || device->port.iobase))
 159                 return -ENODEV;
 160
 161         if (!device->baud) {
 162                 struct uart_port *port = &device->port;
 163                 unsigned int ier;
 164
 165                 /* assume the device was initialized, only mask interrupts */
 166                 ier = serial8250_early_in(port, UART_IER);
 167                 serial8250_early_out(port, UART_IER, ier & UART_IER_UUE);
 168         } else
 169                 init_port(device);
 170
 171         device->con->write = early_serial8250_write;
 172         device->con->read = early_serial8250_read;
 173         return 0;
 174 }
 175 EARLYCON_DECLARE(uart8250, early_serial8250_setup);
 176 EARLYCON_DECLARE(uart, early_serial8250_setup);
 177 OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
 178 OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
 179 OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
 180 OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
 181
 182 #ifdef CONFIG_SERIAL_8250_OMAP
 183
 184 static int __init early_omap8250_setup(struct earlycon_device *device,
 185                                        const char *options)
 186 {
 187         struct uart_port *port = &device->port;
 188
 189         if (!(device->port.membase || device->port.iobase))
 190                 return -ENODEV;
 191
 192         port->regshift = 2;
 193         device->con->write = early_serial8250_write;
 194         return 0;
 195 }
 196
 197 OF_EARLYCON_DECLARE(omap8250, "ti,omap2-uart", early_omap8250_setup);
 198 OF_EARLYCON_DECLARE(omap8250, "ti,omap3-uart", early_omap8250_setup);
 199 OF_EARLYCON_DECLARE(omap8250, "ti,omap4-uart", early_omap8250_setup);
 200 OF_EARLYCON_DECLARE(omap8250, "ti,am654-uart", early_omap8250_setup);
 201
 202 #endif
 203
 204 #ifdef CONFIG_SERIAL_8250_RT288X
 205
 206 static int __init early_au_setup(struct earlycon_device *dev, const char *opt)
 207 {
 208         dev->port.serial_in = au_serial_in;
 209         dev->port.serial_out = au_serial_out;
 210         dev->port.iotype = UPIO_AU;
 211         dev->con->write = early_serial8250_write;
 212         return 0;
 213 }
 214 OF_EARLYCON_DECLARE(palmchip, "ralink,rt2880-uart", early_au_setup);
 215
 216 #endif