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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>
- 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)
- ;
- }
- struct earlycon_match {
- const char *name;
- void (*printch)(char ch);
- };
- static const struct earlycon_match earlycon_match[] __initconst = {
- { .name = "pl011", .printch = pl011_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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