android_kernel_xiaomi_sm8350/arch/powerpc/kernel/udbg.c
Andrew Klossner af9c724907 powerpc/udbg: Fix lost byte during console handover; change LFCR to CRLF
When the console is on a serial port to be driven by serial8250, a
character can be lost from the end of the first line in the two-line
sequence

	serial8250.0: ttyS0 at MMIO 0xe0004500 (irq = 42) is a 16550A
	console handover: boot [udbg0] -> real [ttyS0]

This happens because udbg_puts or udbg_write stuff the last byte of
the line into the Tx FIFO and return, whereupon the serial8250
initialization code immediately empties that FIFO.  The fix: udbg_puts
and udbg_write now wait for the Tx FIFO to clear before returning.
This delays the system by one additional serial frame time for each
line written by udbg, but the effect is not noticeable, a cumulative
17 milliseconds for 200 lines of early printk output at 115200 baud.

Also, the routines in udbg_16550.c now emit CRLF instead of LFCR.
Linux makes a point of emitting CRLF because, when serial output is
captured to a file, LFCR sequences can confuse text editors.  See
http://lkml.org/lkml/2006/2/4/50 for some history.

Signed-off-by: Andrew Klossner <andrew@cesa.opbu.xerox.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2009-03-11 17:11:34 +11:00

193 lines
4.0 KiB
C

/*
* polling mode stateless debugging stuff, originally for NS16550 Serial Ports
*
* c 2001 PPC 64 Team, IBM Corp
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <stdarg.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/console.h>
#include <linux/init.h>
#include <asm/processor.h>
#include <asm/udbg.h>
void (*udbg_putc)(char c);
void (*udbg_flush)(void);
int (*udbg_getc)(void);
int (*udbg_getc_poll)(void);
/*
* Early debugging facilities. You can enable _one_ of these via .config,
* if you do so your kernel _will not boot_ on anything else. Be careful.
*/
void __init udbg_early_init(void)
{
#if defined(CONFIG_PPC_EARLY_DEBUG_LPAR)
/* For LPAR machines that have an HVC console on vterm 0 */
udbg_init_debug_lpar();
#elif defined(CONFIG_PPC_EARLY_DEBUG_G5)
/* For use on Apple G5 machines */
udbg_init_pmac_realmode();
#elif defined(CONFIG_PPC_EARLY_DEBUG_RTAS_PANEL)
/* RTAS panel debug */
udbg_init_rtas_panel();
#elif defined(CONFIG_PPC_EARLY_DEBUG_RTAS_CONSOLE)
/* RTAS console debug */
udbg_init_rtas_console();
#elif defined(CONFIG_PPC_EARLY_DEBUG_MAPLE)
/* Maple real mode debug */
udbg_init_maple_realmode();
#elif defined(CONFIG_PPC_EARLY_DEBUG_ISERIES)
/* For iSeries - hit Ctrl-x Ctrl-x to see the output */
udbg_init_iseries();
#elif defined(CONFIG_PPC_EARLY_DEBUG_BEAT)
udbg_init_debug_beat();
#elif defined(CONFIG_PPC_EARLY_DEBUG_PAS_REALMODE)
udbg_init_pas_realmode();
#elif defined(CONFIG_BOOTX_TEXT)
udbg_init_btext();
#elif defined(CONFIG_PPC_EARLY_DEBUG_44x)
/* PPC44x debug */
udbg_init_44x_as1();
#elif defined(CONFIG_PPC_EARLY_DEBUG_40x)
/* PPC40x debug */
udbg_init_40x_realmode();
#elif defined(CONFIG_PPC_EARLY_DEBUG_CPM)
udbg_init_cpm();
#endif
#ifdef CONFIG_PPC_EARLY_DEBUG
console_loglevel = 10;
#endif
}
/* udbg library, used by xmon et al */
void udbg_puts(const char *s)
{
if (udbg_putc) {
char c;
if (s && *s != '\0') {
while ((c = *s++) != '\0')
udbg_putc(c);
}
if (udbg_flush)
udbg_flush();
}
#if 0
else {
printk("%s", s);
}
#endif
}
int udbg_write(const char *s, int n)
{
int remain = n;
char c;
if (!udbg_putc)
return 0;
if (s && *s != '\0') {
while (((c = *s++) != '\0') && (remain-- > 0)) {
udbg_putc(c);
}
}
if (udbg_flush)
udbg_flush();
return n - remain;
}
int udbg_read(char *buf, int buflen)
{
char *p = buf;
int i, c;
if (!udbg_getc)
return 0;
for (i = 0; i < buflen; ++i) {
do {
c = udbg_getc();
if (c == -1 && i == 0)
return -1;
} while (c == 0x11 || c == 0x13);
if (c == 0 || c == -1)
break;
*p++ = c;
}
return i;
}
#define UDBG_BUFSIZE 256
void udbg_printf(const char *fmt, ...)
{
char buf[UDBG_BUFSIZE];
va_list args;
va_start(args, fmt);
vsnprintf(buf, UDBG_BUFSIZE, fmt, args);
udbg_puts(buf);
va_end(args);
}
void __init udbg_progress(char *s, unsigned short hex)
{
udbg_puts(s);
udbg_puts("\n");
}
/*
* Early boot console based on udbg
*/
static void udbg_console_write(struct console *con, const char *s,
unsigned int n)
{
udbg_write(s, n);
}
static struct console udbg_console = {
.name = "udbg",
.write = udbg_console_write,
.flags = CON_PRINTBUFFER | CON_ENABLED | CON_BOOT | CON_ANYTIME,
.index = 0,
};
static int early_console_initialized;
/*
* Called by setup_system after ppc_md->probe and ppc_md->early_init.
* Call it again after setting udbg_putc in ppc_md->setup_arch.
*/
void __init register_early_udbg_console(void)
{
if (early_console_initialized)
return;
if (!udbg_putc)
return;
if (strstr(boot_command_line, "udbg-immortal")) {
printk(KERN_INFO "early console immortal !\n");
udbg_console.flags &= ~CON_BOOT;
}
early_console_initialized = 1;
register_console(&udbg_console);
}
#if 0 /* if you want to use this as a regular output console */
console_initcall(register_udbg_console);
#endif