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/*
* Earlyprintk support.
*
* Copyright (C) 2012 ARM Ltd.
* Author: Catalin Marinas <catalin.marinas@arm.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/kernel.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/amba/serial.h>
#include <linux/serial_reg.h>
static void __iomem *early_base;
static void (*printch)(char ch);
/*
* PL011 single character TX.
*/
static void pl011_printch(char ch)
{
while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_TXFF)
;
writeb_relaxed(ch, early_base + UART01x_DR);
while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_BUSY)
;
}
/*
* Semihosting-based debug console
*/
static void smh_printch(char ch)
{
asm volatile("mov x1, %0\n"
"mov x0, #3\n"
"hlt 0xf000\n"
: : "r" (&ch) : "x0", "x1", "memory");
}
/*
* 8250/16550 (8-bit aligned registers) single character TX.
*/
static void uart8250_8bit_printch(char ch)
{
while (!(readb_relaxed(early_base + UART_LSR) & UART_LSR_THRE))
;
writeb_relaxed(ch, early_base + UART_TX);
}
/*
* 8250/16550 (32-bit aligned registers) single character TX.
*/
static void uart8250_32bit_printch(char ch)
{
while (!(readl_relaxed(early_base + (UART_LSR << 2)) & UART_LSR_THRE))
;
writel_relaxed(ch, early_base + (UART_TX << 2));
}
struct earlycon_match {
const char *name;
void (*printch)(char ch);
};
static const struct earlycon_match earlycon_match[] __initconst = {
{ .name = "pl011", .printch = pl011_printch, },
{ .name = "smh", .printch = smh_printch, },
{ .name = "uart8250-8bit", .printch = uart8250_8bit_printch, },
{ .name = "uart8250-32bit", .printch = uart8250_32bit_printch, },
{}
};
static void early_write(struct console *con, const char *s, unsigned n)
{
while (n-- > 0) {
if (*s == '\n')
printch('\r');
printch(*s);
s++;
}
}
static struct console early_console = {
.name = "earlycon",
.write = early_write,
.flags = CON_PRINTBUFFER | CON_BOOT,
.index = -1,
};
/*
* Parse earlyprintk=... parameter in the format:
*
* <name>[,<addr>][,<options>]
*
* and register the early console. It is assumed that the UART has been
* initialised by the bootloader already.
*/
static int __init setup_early_printk(char *buf)
{
const struct earlycon_match *match = earlycon_match;
phys_addr_t paddr = 0;
if (!buf) {
pr_warning("No earlyprintk arguments passed.\n");
return 0;
}
while (match->name) {
size_t len = strlen(match->name);
if (!strncmp(buf, match->name, len)) {
buf += len;
break;
}
match++;
}
if (!match->name) {
pr_warning("Unknown earlyprintk arguments: %s\n", buf);
return 0;
}
/* I/O address */
if (!strncmp(buf, ",0x", 3)) {
char *e;
paddr = simple_strtoul(buf + 1, &e, 16);
buf = e;
}
/* no options parsing yet */
if (paddr)
early_base = early_io_map(paddr, EARLYCON_IOBASE);
printch = match->printch;
register_console(&early_console);
return 0;
}
early_param("earlyprintk", setup_early_printk);
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