Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752195Ab0GJUyU (ORCPT ); Sat, 10 Jul 2010 16:54:20 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:58913 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751321Ab0GJUyT (ORCPT ); Sat, 10 Jul 2010 16:54:19 -0400 Message-ID: <4C38DCD3.8020302@kernel.org> Date: Sat, 10 Jul 2010 13:49:23 -0700 From: Yinghai Lu User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100520 SUSE/3.0.5 Thunderbird/3.0.5 MIME-Version: 1.0 To: Pekka Enberg CC: hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, Cyrill Gorcunov , Ingo Molnar Subject: Re: [PATCH v2] x86: Early-boot serial I/O support References: <1278790820-1817-1-git-send-email-penberg@cs.helsinki.fi> In-Reply-To: <1278790820-1817-1-git-send-email-penberg@cs.helsinki.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: acsmt355.oracle.com [141.146.40.155] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090207.4C38DDA4.005E,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8258 Lines: 300 On 07/10/2010 12:40 PM, Pekka Enberg wrote: > 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 > Cc: Ingo Molnar > Cc: Yinghai Lu > Signed-off-by: Pekka Enberg > --- > 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); > +} can you analyze "console=uart8250,io,0x3f8,115200n8" instead? that is equal to "earlyprintk=ttyS0,115200 console=ttyS0,115200" so we only use one for all. also like to kill earlyprintk=ttyS0,115200 to favor earlycon Thanks Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/