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Message-Id: <1278790820-1817-1-git-send-email-penberg@cs.helsinki.fi>
Date: Sat, 10 Jul 2010 22:40:20 +0300
From: Pekka Enberg <penberg@...helsinki.fi>
To: hpa@...or.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
Pekka Enberg <penberg@...helsinki.fi>,
Cyrill Gorcunov <gorcunov@...il.com>,
Ingo Molnar <mingo@...hat.com>, Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH v2] x86: Early-boot serial I/O support
This patch adds serial I/O support to very early boot printf(). It's useful for
debugging boot code when running Linux under KVM, for example. The actual code
was lifted from early printk.
Cc: Cyrill Gorcunov <gorcunov@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Yinghai Lu <yinghai@...nel.org>
Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
---
v1 -> v2:
- Use 'earlyprintk' kernel parameter to determine whether to use
early serial or not as suggested by Yinghai and hpa.
arch/x86/boot/boot.h | 16 +++++++
arch/x86/boot/main.c | 3 +
arch/x86/boot/string.c | 41 ++++++++++++++++++
arch/x86/boot/tty.c | 111 +++++++++++++++++++++++++++++++++++++++++++++---
4 files changed, 165 insertions(+), 6 deletions(-)
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 98239d2..f05b5ac 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -37,6 +37,8 @@
extern struct setup_header hdr;
extern struct boot_params boot_params;
+#define cpu_relax() asm volatile("rep; nop" ::: "memory")
+
/* Basic port I/O */
static inline void outb(u8 v, u16 port)
{
@@ -203,6 +205,17 @@ static inline int isdigit(int ch)
return (ch >= '0') && (ch <= '9');
}
+static inline int isxdigit(int ch)
+{
+ if (isdigit(ch))
+ return true;
+
+ if ((ch >= 'a') && (ch <= 'f'))
+ return true;
+
+ return (ch >= 'A') && (ch <= 'F');
+}
+
/* Heap -- available for dynamic lists. */
extern char _end[];
extern char *HEAP;
@@ -329,10 +342,13 @@ void initregs(struct biosregs *regs);
/* string.c */
int strcmp(const char *str1, const char *str2);
+int strncmp(const char *cs, const char *ct, size_t count);
size_t strnlen(const char *s, size_t maxlen);
unsigned int atou(const char *s);
+unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base);
/* tty.c */
+void console_init(void);
void puts(const char *);
void putchar(int);
int getchar(void);
diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index 140172b..4ef1a33 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -130,6 +130,9 @@ void main(void)
/* First, copy the boot header into the "zeropage" */
copy_boot_params();
+ /* Initialize the early-boot console */
+ console_init();
+
/* End of heap check */
init_heap();
diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index f94b7a0..aba29df 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -30,6 +30,22 @@ int strcmp(const char *str1, const char *str2)
return 0;
}
+int strncmp(const char *cs, const char *ct, size_t count)
+{
+ unsigned char c1, c2;
+
+ while (count) {
+ c1 = *cs++;
+ c2 = *ct++;
+ if (c1 != c2)
+ return c1 < c2 ? -1 : 1;
+ if (!c1)
+ break;
+ count--;
+ }
+ return 0;
+}
+
size_t strnlen(const char *s, size_t maxlen)
{
const char *es = s;
@@ -48,3 +64,28 @@ unsigned int atou(const char *s)
i = i * 10 + (*s++ - '0');
return i;
}
+
+/* Works only for digits and letters, but small and fast */
+#define TOLOWER(x) ((x) | 0x20)
+
+unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
+{
+ unsigned long long result = 0;
+
+ if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
+ cp += 2;
+
+ while (isxdigit(*cp)) {
+ unsigned int value;
+
+ value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+ if (value >= base)
+ break;
+ result = result * base + value;
+ cp++;
+ }
+ if (endp)
+ *endp = (char *)cp;
+
+ return result;
+}
diff --git a/arch/x86/boot/tty.c b/arch/x86/boot/tty.c
index 01ec69c..f3ceee2 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -10,23 +10,51 @@
* ----------------------------------------------------------------------- */
/*
- * Very simple screen I/O
- * XXX: Probably should add very simple serial I/O?
+ * Very simple screen and serial I/O
*/
#include "boot.h"
+#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
+
+static int early_serial_base;
+
+#define XMTRDY 0x20
+
+#define DLAB 0x80
+
+#define TXR 0 /* Transmit register (WRITE) */
+#define RXR 0 /* Receive register (READ) */
+#define IER 1 /* Interrupt Enable */
+#define IIR 2 /* Interrupt ID */
+#define FCR 2 /* FIFO control */
+#define LCR 3 /* Line control */
+#define MCR 4 /* Modem control */
+#define LSR 5 /* Line Status */
+#define MSR 6 /* Modem Status */
+#define DLL 0 /* Divisor Latch Low */
+#define DLH 1 /* Divisor latch High */
+
+#define DEFAULT_BAUD 9600
+
/*
* These functions are in .inittext so they can be used to signal
* error during initialization.
*/
-void __attribute__((section(".inittext"))) putchar(int ch)
+static void __attribute__((section(".inittext"))) serial_putchar(int ch)
{
- struct biosregs ireg;
+ unsigned timeout = 0xffff;
- if (ch == '\n')
- putchar('\r'); /* \n -> \r\n */
+ while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+ cpu_relax();
+
+ outb(ch, early_serial_base + TXR);
+}
+
+static void __attribute__((section(".inittext"))) bios_putchar(int ch)
+{
+ struct biosregs ireg;
initregs(&ireg);
ireg.bx = 0x0007;
@@ -36,6 +64,17 @@ void __attribute__((section(".inittext"))) putchar(int ch)
intcall(0x10, &ireg, NULL);
}
+void __attribute__((section(".inittext"))) putchar(int ch)
+{
+ if (ch == '\n')
+ putchar('\r'); /* \n -> \r\n */
+
+ bios_putchar(ch);
+
+ if (early_serial_base != 0)
+ serial_putchar(ch);
+}
+
void __attribute__((section(".inittext"))) puts(const char *str)
{
while (*str)
@@ -112,3 +151,63 @@ int getchar_timeout(void)
return 0; /* Timeout! */
}
+
+static void early_serial_init(int baud)
+{
+ unsigned char c;
+ unsigned divisor;
+
+ outb(0x3, early_serial_base + LCR); /* 8n1 */
+ outb(0, early_serial_base + IER); /* no interrupt */
+ outb(0, early_serial_base + FCR); /* no fifo */
+ outb(0x3, early_serial_base + MCR); /* DTR + RTS */
+
+ divisor = 115200 / baud;
+ c = inb(early_serial_base + LCR);
+ outb(c | DLAB, early_serial_base + LCR);
+ outb(divisor & 0xff, early_serial_base + DLL);
+ outb((divisor >> 8) & 0xff, early_serial_base + DLH);
+ outb(c & ~DLAB, early_serial_base + LCR);
+}
+
+void console_init(void)
+{
+ int baud = DEFAULT_BAUD;
+ char arg[32];
+ int pos = 0;
+
+ if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
+ char *e;
+
+ if (!strncmp(arg, "serial", 6)) {
+ early_serial_base = DEFAULT_SERIAL_PORT;
+ pos += 6;
+ }
+
+ if (arg[pos] == ',')
+ pos++;
+
+ if (!strncmp(arg, "ttyS", 4)) {
+ static const int bases[] = { 0x3f8, 0x2f8 };
+ int port = 0;
+
+ if (!strncmp(arg + pos, "ttyS", 4))
+ pos += 4;
+
+ if (arg[pos++] == '1')
+ port = 1;
+
+ early_serial_base = bases[port];
+ }
+
+ if (arg[pos] == ',')
+ pos++;
+
+ baud = simple_strtoull(arg + pos, &e, 0);
+ if (baud == 0 || arg + pos == e)
+ baud = DEFAULT_BAUD;
+ }
+
+ if (early_serial_base != 0)
+ early_serial_init(baud);
+}
--
1.6.3.3
--
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