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