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Date: Tue, 13 Jul 2010 13:35:17 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: Pekka Enberg <penberg@...helsinki.fi>
CC: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: Setup early console as early as possible
On 07/13/2010 10:43 AM, Pekka Enberg wrote:
> Hi Yingahai,
>
> Yinghai Lu wrote:
>> On 07/12/2010 08:47 AM, H. Peter Anvin wrote:
>>> On 07/12/2010 01:58 AM, Pekka Enberg wrote:
>>>> Hi Yinghai,
>>>>
>>>> Yinghai Lu wrote:
>>>>> Analyze "console=uart8250,io,0x3f8,115200n8" in
>>>>> i386_start_kernel/x86_64_start_kernel,
>>>>> and call setup_early_serial8250_console() to init early serial
>>>>> console.
>>>>>
>>>>> only can handle io port kind of 8250. because mmio need ioremap.
>>>>>
>>>>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>>> What's the purpose of this patch? Does it make my early boot I/O patch
>>>> obsolete?
>>>>
>>>> Pekka
>>> No, they're complementary. Your patch serial-port enables the RM
>>> kernel, whereas Yinghai pushes the initialization earlier in the PM
>>> kernel.
>>
>> yes. cover more range.
>>
>> Can you consider to ask Pekka to anaylze "console=uart8250,io,
>> 0x3f8,115200n8" instead?
>>
>> it looks like we can remove "earlyprintk=ttyS0,115200", or
>> "earlyprintk=serial" etc.
>>
>> earlycon=uart8250 or console=uart8250 should be better than earlyprintk.
>> because it is shared between different archs already.
>
> So just to clarify: I wasn't ignoring your comment here. I simply
> followed hpa's recommendation on which I also happen to agree with
> completely. ;-)
never mind.
following patch add that checking.
also you missed simple_guess_base(), your patch may have problem with baud rate reading.
baud = simple_strtoull(arg + pos, &e, 0);
if (baud == 0 || arg + pos == e)
baud = DEFAULT_BAUD;
and your copied simple_strtoull does not calling simple_guess_base(), so base will 0.
so you are always using DEFAULT_BAUD.
Thanks
Yinghai Lu
[PATCH] x86: make boot code to analyze console=uart8250 too
So we use console=uart8250,io,0x2f8,115200n all the way
Also add back simple_guess_base(), otherwise those simple_strtoull(,,0) are not
going to work.
Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
arch/x86/boot/string.c | 22 ++++++++++++++++++
arch/x86/boot/tty.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 80 insertions(+), 1 deletion(-)
Index: linux-2.6/arch/x86/boot/tty.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/tty.c
+++ linux-2.6/arch/x86/boot/tty.c
@@ -170,7 +170,7 @@ static void early_serial_init(int baud)
outb(c & ~DLAB, early_serial_base + LCR);
}
-void console_init(void)
+static int parse_earlyprintk(void)
{
int baud = DEFAULT_BAUD;
char arg[32];
@@ -208,6 +208,63 @@ void console_init(void)
baud = DEFAULT_BAUD;
}
+ return baud;
+}
+
+#define BASE_BAUD (1843200/16)
+static unsigned int probe_baud(int port)
+{
+ unsigned char lcr, dll, dlh;
+ unsigned int quot;
+
+ lcr = inb(port + LCR);
+ outb(lcr | DLAB, port + LCR);
+ dll = inb(port + DLL);
+ dlh = inb(port + DLH);
+ outb(lcr, port + LCR);
+ quot = (dlh << 8) | dll;
+
+ return BASE_BAUD / quot;
+}
+
+static int parse_console_uart8250(void)
+{
+ char optstr[64], *options;
+ int baud = DEFAULT_BAUD;
+
+ /*
+ * console=uart8250,io,0x3f8,115200n8
+ * need to make sure it is last one console !
+ */
+ if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
+ return baud;
+
+ options = optstr;
+
+ if (!strncmp(options, "uart8250,io,", 12))
+ early_serial_base = simple_strtoull(options + 12, &options, 0);
+ else if (!strncmp(options, "uart,io,", 8))
+ early_serial_base = simple_strtoull(options + 8, &options, 0);
+ else
+ return baud;
+
+ if (options && (options[0] == ','))
+ baud = simple_strtoull(options + 1, &options, 0);
+ else
+ baud = probe_baud(early_serial_base);
+
+ return baud;
+}
+
+void console_init(void)
+{
+ int baud;
+
+ baud = parse_earlyprintk();
+
+ if (!early_serial_base)
+ baud = parse_console_uart8250();
+
if (early_serial_base != 0)
early_serial_init(baud);
}
Index: linux-2.6/arch/x86/boot/string.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/string.c
+++ linux-2.6/arch/x86/boot/string.c
@@ -68,10 +68,32 @@ unsigned int atou(const char *s)
/* Works only for digits and letters, but small and fast */
#define TOLOWER(x) ((x) | 0x20)
+static unsigned int simple_guess_base(const char *cp)
+{
+ if (cp[0] == '0') {
+ if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
+ return 16;
+ else
+ return 8;
+ } else {
+ return 10;
+ }
+}
+
+/**
+ * simple_strtoull - convert a string to an unsigned long long
+ * @cp: The start of the string
+ * @endp: A pointer to the end of the parsed string will be placed here
+ * @base: The number base to use
+ */
+
unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
{
unsigned long long result = 0;
+ if (!base)
+ base = simple_guess_base(cp);
+
if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2;
--
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