Messages in this thread Patch in this message | | | Date | Fri, 18 Jul 2003 08:39:29 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: Linux 2.4.20 RTC Timer bug |
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On Fri, 18 Jul 2003, Willy Tarreau wrote:
> On Thu, Jul 17, 2003 at 04:38:05PM -0400, Richard B. Johnson wrote: > [SNIPPED...]
> > Or leaves the index register somewhere that a power-fail sequence will > > trash a checksummed register.. > > yes, that's possible too. > > > > is it in the spec that it has to be set to 0xFF or because you chose this > value since it's out of the checksummed area ? On older chips, it will be > equal to 0x3F (0xBF if we include NMI) and on newer ones, 0x7F. If the BIOS > uses these bytes to write the checksum of the advanced setup, it might be > dangerous. I would personaly prefer to set it to something not checked, such > as the alarm, status, or so (except if the chip does a special case of FF).
Well, yes. It probably should be left at status register 'D'. Here's a patch. Let's see if the Linux folks accept it....
Problem: Power failure can cause CMOS checksum corruption and failure to boot. Patch (tested -- running now):
--- linux-2.4.20/include/asm-i386/mc146818rtc.h.orig Thu Jul 17 15:06:33 2003 +++ linux-2.4.20/include/asm-i386/mc146818rtc.h Fri Jul 18 08:01:58 2003 @@ -10,18 +10,28 @@ #define RTC_PORT(x) (0x70 + (x)) #define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */ #endif +#define RTC_FAILSAFE 0x0d +#define NMI_ENABLE 0x80
/* * The yet supported machines all access the RTC index register via * an ISA port access but the way to access the date register differs ... + * Modified 18-JUL-2003 + * Willy Tarreau <willy@w.ods.org>, Richard Johnson <rjohnson@analogic.com> + * Leave index register at status register D so a power failure doesn't + * corrupt checksummed CMOS. Keep NMI bit enabled (in case it really exists). */ #define CMOS_READ(addr) ({ \ -outb_p((addr),RTC_PORT(0)); \ -inb_p(RTC_PORT(1)); \ +int __val; \ +outb_p((addr)|NMI_ENABLE,RTC_PORT(0)); \ +__val = inb_p(RTC_PORT(1)); \ +outb_p(RTC_FAILSAFE|NMI_ENABLE, RTC_PORT(0)); \ +__val; \ }) #define CMOS_WRITE(val, addr) ({ \ -outb_p((addr),RTC_PORT(0)); \ +outb_p((addr)|NMI_ENABLE,RTC_PORT(0)); \ outb_p((val),RTC_PORT(1)); \ +outb_p(RTC_FAILSAFE|NMI_ENABLE, RTC_PORT(0)); \ })
#define RTC_IRQ 8
Cheers, Dick Johnson Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips). Note 96.31% of all statistics are fiction.
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