1 /*
2 * Earlyprintk support.
3 *
4 * Copyright (C) 2012 ARM Ltd.
5 * Author: Catalin Marinas <catalin.marinas@arm.com>
6 *
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.
10 *
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.
15 *
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/>.
18 */
19 #include <linux/kernel.h>
20 #include <linux/console.h>
21 #include <linux/init.h>
22 #include <linux/string.h>
23 #include <linux/mm.h>
24 #include <linux/io.h>
25
26 #include <linux/amba/serial.h>
27 #include <linux/serial_reg.h>
28
29 #include <asm/fixmap.h>
30
31 #define UART_USR 31 /* I/O: uart status Register */
32 #define UART_USR_NF 0x02 /* Tansmit fifo not full */
33
34 static void __iomem *early_base;
35 static void (*printch)(char ch);
36
37 /*
38 * PL011 single character TX.
39 */
pl011_printch(char ch)40 static void pl011_printch(char ch)
41 {
42 while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_TXFF)
43 ;
44 writeb_relaxed(ch, early_base + UART01x_DR);
45 while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_BUSY)
46 ;
47 }
48
49 /*
50 * Semihosting-based debug console
51 */
smh_printch(char ch)52 static void smh_printch(char ch)
53 {
54 asm volatile("mov x1, %0\n"
55 "mov x0, #3\n"
56 "hlt 0xf000\n"
57 : : "r" (&ch) : "x0", "x1", "memory");
58 }
59
60 /*
61 * 8250/16550 (8-bit aligned registers) single character TX.
62 */
uart8250_8bit_printch(char ch)63 static void uart8250_8bit_printch(char ch)
64 {
65 while (!(readb_relaxed(early_base + UART_LSR) & UART_LSR_THRE))
66 ;
67 writeb_relaxed(ch, early_base + UART_TX);
68 }
69
70 /*
71 * 8250/16550 (32-bit aligned registers) single character TX.
72 */
uart8250_32bit_printch(char ch)73 static void uart8250_32bit_printch(char ch)
74 {
75 while (!(readl_relaxed(early_base + (UART_LSR << 2)) & UART_LSR_THRE))
76 ;
77 writel_relaxed(ch, early_base + (UART_TX << 2));
78 }
79
80 /*
81 * sunxi-uart single character TX.
82 */
sunxi_uart_printch(char ch)83 static void sunxi_uart_printch(char ch)
84 {
85
86 while (!(readl_relaxed(early_base + (UART_USR << 2)) & UART_USR_NF))
87 ;
88
89 writel_relaxed(ch, early_base + (UART_TX << 2));
90 }
91
92 struct earlycon_match {
93 const char *name;
94 void (*printch)(char ch);
95 };
96
97 static const struct earlycon_match earlycon_match[] __initconst = {
98 { .name = "pl011", .printch = pl011_printch, },
99 { .name = "smh", .printch = smh_printch, },
100 { .name = "uart8250-8bit", .printch = uart8250_8bit_printch, },
101 { .name = "uart8250-32bit", .printch = uart8250_32bit_printch, },
102 { .name = "sunxi-uart", .printch = sunxi_uart_printch, },
103 {}
104 };
105
early_write(struct console * con,const char * s,unsigned n)106 static void early_write(struct console *con, const char *s, unsigned n)
107 {
108 while (n-- > 0) {
109 if (*s == '\n')
110 printch('\r');
111 printch(*s);
112 s++;
113 }
114 }
115
116 static struct console early_console_dev = {
117 .name = "earlycon",
118 .write = early_write,
119 .flags = CON_PRINTBUFFER | CON_BOOT,
120 .index = -1,
121 };
122
123 /*
124 * Parse earlyprintk=... parameter in the format:
125 *
126 * <name>[,<addr>][,<options>]
127 *
128 * and register the early console. It is assumed that the UART has been
129 * initialised by the bootloader already.
130 */
setup_early_printk(char * buf)131 static int __init setup_early_printk(char *buf)
132 {
133 const struct earlycon_match *match = earlycon_match;
134 phys_addr_t paddr = 0;
135 char *e;
136
137 if (!buf) {
138 pr_warn("No earlyprintk arguments passed.\n");
139 return 0;
140 }
141
142 while (match->name) {
143 size_t len = strlen(match->name);
144 if (!strncmp(buf, match->name, len)) {
145 buf += len;
146 break;
147 }
148 match++;
149 }
150 if (!match->name) {
151 pr_warn("Unknown earlyprintk arguments: %s\n", buf);
152 return 0;
153 }
154
155 /* I/O address */
156 if (!strncmp(buf, ",0x", 3)) {
157 paddr = simple_strtoul(buf + 1, &e, 16);
158 }
159 /* no options parsing yet */
160
161 if (paddr) {
162 set_fixmap_io(FIX_EARLYCON_MEM_BASE, paddr);
163 early_base = (void __iomem *)(fix_to_virt(FIX_EARLYCON_MEM_BASE)
164 |(paddr & (PAGE_SIZE - 1)));
165 }
166 printch = match->printch;
167 early_console = &early_console_dev;
168 register_console(&early_console_dev);
169
170 return 0;
171 }
172
173 early_param("earlyprintk", setup_early_printk);
174