-
/*
* Routines to indentify additional cpu features that are scattered in
* cpuid space.
*/
-
#include <linux/cpu.h>
#include <asm/pat.h>
#ifdef CONFIG_X86_PAT
void __cpuinit validate_pat_support(struct cpuinfo_x86 *c)
{
+ if (!cpu_has_pat)
+ pat_disable("PAT not supported by CPU.");
+
switch (c->x86_vendor) {
- case X86_VENDOR_AMD:
- if (c->x86 >= 0xf && c->x86 <= 0x11)
- return;
- break;
case X86_VENDOR_INTEL:
- if (c->x86 == 0xF || (c->x86 == 6 && c->x86_model >= 15))
+ /*
+ * There is a known erratum on Pentium III and Core Solo
+ * and Core Duo CPUs.
+ * " Page with PAT set to WC while associated MTRR is UC
+ * may consolidate to UC "
+ * Because of this erratum, it is better to stick with
+ * setting WC in MTRR rather than using PAT on these CPUs.
+ *
+ * Enable PAT WC only on P4, Core 2 or later CPUs.
+ */
+ if (c->x86 > 0x6 || (c->x86 == 6 && c->x86_model >= 15))
return;
- break;
+
+ pat_disable("PAT WC disabled due to known CPU erratum.");
+ return;
+
+ case X86_VENDOR_AMD:
+ case X86_VENDOR_CENTAUR:
+ case X86_VENDOR_TRANSMETA:
+ return;
}
- pat_disable(cpu_has_pat ?
- "PAT disabled. Not yet verified on this CPU type." :
- "PAT not supported by CPU.");
+ pat_disable("PAT disabled. Not yet verified on this CPU type.");
}
#endif