4 * Copyright (C) 2012 ARM Ltd.
5 * Author: Catalin Marinas <catalin.marinas@arm.com>
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
19 #include <linux/kernel.h>
20 #include <linux/console.h>
21 #include <linux/init.h>
22 #include <linux/string.h>
26 #include <linux/amba/serial.h>
27 #include <linux/serial_reg.h>
29 #include <asm/fixmap.h>
31 static void __iomem *early_base;
32 static void (*printch)(char ch);
35 * PL011 single character TX.
37 static void pl011_printch(char ch)
39 while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_TXFF)
41 writeb_relaxed(ch, early_base + UART01x_DR);
42 while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_BUSY)
47 * Semihosting-based debug console
49 static void smh_printch(char ch)
51 asm volatile("mov x1, %0\n"
54 : : "r" (&ch) : "x0", "x1", "memory");
58 * 8250/16550 (8-bit aligned registers) single character TX.
60 static void uart8250_8bit_printch(char ch)
62 while (!(readb_relaxed(early_base + UART_LSR) & UART_LSR_THRE))
64 writeb_relaxed(ch, early_base + UART_TX);
68 * 8250/16550 (32-bit aligned registers) single character TX.
70 static void uart8250_32bit_printch(char ch)
72 while (!(readl_relaxed(early_base + (UART_LSR << 2)) & UART_LSR_THRE))
74 writel_relaxed(ch, early_base + (UART_TX << 2));
77 struct earlycon_match {
79 void (*printch)(char ch);
82 static const struct earlycon_match earlycon_match[] __initconst = {
83 { .name = "pl011", .printch = pl011_printch, },
84 { .name = "smh", .printch = smh_printch, },
85 { .name = "uart8250-8bit", .printch = uart8250_8bit_printch, },
86 { .name = "uart8250-32bit", .printch = uart8250_32bit_printch, },
90 static void early_write(struct console *con, const char *s, unsigned n)
100 static struct console early_console_dev = {
102 .write = early_write,
103 .flags = CON_PRINTBUFFER | CON_BOOT,
108 * Parse earlyprintk=... parameter in the format:
110 * <name>[,<addr>][,<options>]
112 * and register the early console. It is assumed that the UART has been
113 * initialised by the bootloader already.
115 static int __init setup_early_printk(char *buf)
117 const struct earlycon_match *match = earlycon_match;
118 phys_addr_t paddr = 0;
121 pr_warning("No earlyprintk arguments passed.\n");
125 while (match->name) {
126 size_t len = strlen(match->name);
127 if (!strncmp(buf, match->name, len)) {
134 pr_warning("Unknown earlyprintk arguments: %s\n", buf);
139 if (!strncmp(buf, ",0x", 3)) {
141 paddr = simple_strtoul(buf + 1, &e, 16);
144 /* no options parsing yet */
147 early_base = (void __iomem *)set_fixmap_offset_io(FIX_EARLYCON_MEM_BASE, paddr);
149 printch = match->printch;
150 early_console = &early_console_dev;
151 register_console(&early_console_dev);
156 early_param("earlyprintk", setup_early_printk);