1/*
2 * Early printk support for Microblaze.
3 *
4 * Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>
5 * Copyright (C) 2007-2009 PetaLogix
6 * Copyright (C) 2003-2006 Yasushi SHOJI <yashi@atmark-techno.com>
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
10 * for more details.
11 */
12
13#include <linux/console.h>
14#include <linux/kernel.h>
15#include <linux/init.h>
16#include <linux/string.h>
17#include <linux/tty.h>
18#include <linux/io.h>
19#include <asm/processor.h>
20#include <linux/fcntl.h>
21#include <asm/setup.h>
22#include <asm/prom.h>
23
24static u32 base_addr;
25
26#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
27static void early_printk_uartlite_putc(char c)
28{
29	/*
30	 * Limit how many times we'll spin waiting for TX FIFO status.
31	 * This will prevent lockups if the base address is incorrectly
32	 * set, or any other issue on the UARTLITE.
33	 * This limit is pretty arbitrary, unless we are at about 10 baud
34	 * we'll never timeout on a working UART.
35	 */
36
37	unsigned retries = 1000000;
38	/* read status bit - 0x8 offset */
39	while (--retries && (in_be32(base_addr + 8) & (1 << 3)))
40		;
41
42	/* Only attempt the iowrite if we didn't timeout */
43	/* write to TX_FIFO - 0x4 offset */
44	if (retries)
45		out_be32(base_addr + 4, c & 0xff);
46}
47
48static void early_printk_uartlite_write(struct console *unused,
49					const char *s, unsigned n)
50{
51	while (*s && n-- > 0) {
52		if (*s == '\n')
53			early_printk_uartlite_putc('\r');
54		early_printk_uartlite_putc(*s);
55		s++;
56	}
57}
58
59static struct console early_serial_uartlite_console = {
60	.name = "earlyser",
61	.write = early_printk_uartlite_write,
62	.flags = CON_PRINTBUFFER | CON_BOOT,
63	.index = -1,
64};
65#endif /* CONFIG_SERIAL_UARTLITE_CONSOLE */
66
67#ifdef CONFIG_SERIAL_8250_CONSOLE
68static void early_printk_uart16550_putc(char c)
69{
70	/*
71	 * Limit how many times we'll spin waiting for TX FIFO status.
72	 * This will prevent lockups if the base address is incorrectly
73	 * set, or any other issue on the UARTLITE.
74	 * This limit is pretty arbitrary, unless we are at about 10 baud
75	 * we'll never timeout on a working UART.
76	 */
77
78	#define UART_LSR_TEMT	0x40 /* Transmitter empty */
79	#define UART_LSR_THRE	0x20 /* Transmit-hold-register empty */
80	#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
81
82	unsigned retries = 10000;
83
84	while (--retries &&
85		!((in_be32(base_addr + 0x14) & BOTH_EMPTY) == BOTH_EMPTY))
86		;
87
88	if (retries)
89		out_be32(base_addr, c & 0xff);
90}
91
92static void early_printk_uart16550_write(struct console *unused,
93					const char *s, unsigned n)
94{
95	while (*s && n-- > 0) {
96		if (*s == '\n')
97			early_printk_uart16550_putc('\r');
98		early_printk_uart16550_putc(*s);
99		s++;
100	}
101}
102
103static struct console early_serial_uart16550_console = {
104	.name = "earlyser",
105	.write = early_printk_uart16550_write,
106	.flags = CON_PRINTBUFFER | CON_BOOT,
107	.index = -1,
108};
109#endif /* CONFIG_SERIAL_8250_CONSOLE */
110
111int __init setup_early_printk(char *opt)
112{
113	int version = 0;
114
115	if (early_console)
116		return 1;
117
118	base_addr = of_early_console(&version);
119	if (base_addr) {
120#ifdef CONFIG_MMU
121		early_console_reg_tlb_alloc(base_addr);
122#endif
123		switch (version) {
124#ifdef CONFIG_SERIAL_UARTLITE_CONSOLE
125		case UARTLITE:
126			pr_info("Early console on uartlite at 0x%08x\n",
127								base_addr);
128			early_console = &early_serial_uartlite_console;
129			break;
130#endif
131#ifdef CONFIG_SERIAL_8250_CONSOLE
132		case UART16550:
133			pr_info("Early console on uart16650 at 0x%08x\n",
134								base_addr);
135			early_console = &early_serial_uart16550_console;
136			break;
137#endif
138		default:
139			pr_info("Unsupported early console %d\n",
140								version);
141			return 1;
142		}
143
144		register_console(early_console);
145		return 0;
146	}
147	return 1;
148}
149
150/* Remap early console to virtual address and do not allocate one TLB
151 * only for early console because of performance degression */
152void __init remap_early_printk(void)
153{
154	if (!early_console)
155		return;
156	pr_info("early_printk_console remapping from 0x%x to ", base_addr);
157	base_addr = (u32) ioremap(base_addr, PAGE_SIZE);
158	pr_cont("0x%x\n", base_addr);
159
160#ifdef CONFIG_MMU
161	/*
162	 * Early console is on the top of skipped TLB entries
163	 * decrease tlb_skip size ensure that hardcoded TLB entry will be
164	 * used by generic algorithm
165	 * FIXME check if early console mapping is on the top by rereading
166	 * TLB entry and compare baseaddr
167	 *  mts  rtlbx, (tlb_skip - 1)
168	 *  nop
169	 *  mfs  rX, rtlblo
170	 *  nop
171	 *  cmp rX, orig_base_addr
172	 */
173	tlb_skip -= 1;
174#endif
175}
176
177void __init disable_early_printk(void)
178{
179	if (!early_console)
180		return;
181	pr_warn("disabling early console\n");
182	unregister_console(early_console);
183	early_console = NULL;
184}
185