From: Duncan Laurie dlaurie@chromium.org
Coreboot was always using MTRR 7 for the write-protect cache entry that covers the ROM and U-boot was removing it. However with 4GB configs we need more MTRRs for the BIOS and so the WP MTRR needs to move. Instead coreboot will always use the last available MTRR that is normally set aside for OS use and U-boot can clear it before the OS.
Signed-off-by: Duncan Laurie dlaurie@chromium.org Signed-off-by: Simon Glass sjg@chromium.org --- arch/x86/cpu/coreboot/coreboot.c | 19 +++++++++++++++---- 1 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/arch/x86/cpu/coreboot/coreboot.c b/arch/x86/cpu/coreboot/coreboot.c index 2912443..ff42661 100644 --- a/arch/x86/cpu/coreboot/coreboot.c +++ b/arch/x86/cpu/coreboot/coreboot.c @@ -94,6 +94,8 @@ void setup_pcat_compatibility() { }
+#define MTRR_TYPE_WP 5 +#define MTRRcap_MSR 0xfe #define MTRRphysBase_MSR(reg) (0x200 + 2 * (reg)) #define MTRRphysMask_MSR(reg) (0x200 + 2 * (reg) + 1)
@@ -101,11 +103,20 @@ int board_final_cleanup(void) { /* Un-cache the ROM so the kernel has one * more MTRR available. + * + * Coreboot should have assigned this to the + * top available variable MTRR. */ - disable_cache(); - wrmsr(MTRRphysBase_MSR(7), 0); - wrmsr(MTRRphysMask_MSR(7), 0); - enable_cache(); + u8 top_mtrr = (rdmsr(MTRRcap_MSR) & 0xff) - 1; + u8 top_type = rdmsr(MTRRphysBase_MSR(top_mtrr)) & 0xff; + + /* Make sure this MTRR is the correct Write-Protected type */ + if (top_type == MTRR_TYPE_WP) { + disable_cache(); + wrmsr(MTRRphysBase_MSR(top_mtrr), 0); + wrmsr(MTRRphysMask_MSR(top_mtrr), 0); + enable_cache(); + }
return 0; }