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Subject[PATCH] Updated cachesize errata
Hi,
The patch below fixes yet another CPU that reports incorrect cachesize.
This one is a little trickier than the previous fixes of this sort, as Intel
have made two CPUs with differing cachesizes, with the same model/stepping.
(Yes, we were meant to distinguish between with cachesize-- doh)

Buggy PIII Tualatins with 256K cache will automatically be fixed up with this patch.
Ones with 512K cache will need an extra boot time argument passed
'cachesize=512'

This bootflag may also come in useful if/when any future CPU makes this mistake
again. Now people can override what the CPU reports, without having to wait
for a kernel patch.

Patch applies to 2.4.13pre1, and 2.4.12-ac1 cleanly, and has been tested on
several boxes here without problems.

regards,

Dave.


diff -urN --exclude-from=/home/davej/.exclude linux/arch/i386/kernel/setup.c linux-dj/arch/i386/kernel/setup.c
--- linux/arch/i386/kernel/setup.c Tue Sep 18 07:03:09 2001
+++ linux-dj/arch/i386/kernel/setup.c Tue Oct 2 18:55:11 2001
@@ -67,6 +67,10 @@
*
* AMD Athlon/Duron/Thunderbird bluesmoke support.
* Dave Jones <davej@suse.de>, April 2001.
+ *
+ * CacheSize bug workaround updates for AMD, Intel & VIA Cyrix.
+ * Dave Jones <davej@suse.de>, September, October 2001.
+ *
*/

/*
@@ -1036,6 +1040,15 @@
#endif
}

+static int cachesize_override __initdata = -1;
+static int __init cachesize_setup(char *str)
+{
+ get_option (&str, &cachesize_override);
+ return 1;
+}
+__setup("cachesize=", cachesize_setup);
+
+
#ifndef CONFIG_X86_TSC
static int tsc_disable __initdata = 0;

@@ -1106,11 +1119,24 @@
l2size = 256;
}

+ /* Intel PIII Tualatin. This comes in two flavours.
+ * One has 256kb of cache, the other 512. We have no way
+ * to determine which, so we use a boottime override
+ * for the 512kb model, and assume 256 otherwise.
+ */
+ if ((c->x86_vendor == X86_VENDOR_INTEL) && (c->x86 == 6) &&
+ (c->x86_model == 11) && (l2size == 0))
+ l2size = 256;
+
/* VIA C3 CPUs (670-68F) need further shifting. */
if (c->x86_vendor == X86_VENDOR_CENTAUR && (c->x86 == 6) &&
((c->x86_model == 7) || (c->x86_model == 8))) {
l2size = l2size >> 8;
}
+
+ /* Allow user to override all this if necessary. */
+ if (cachesize_override != -1)
+ l2size = cachesize_override;

if ( l2size == 0 )
return; /* Again, no L2 cache is possible */

--
| Dave Jones. http://www.codemonkey.org.uk
| SuSE Labs .
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