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-rw-r--r--src/include/cpu/x86/mtrr.h18
1 files changed, 14 insertions, 4 deletions
diff --git a/src/include/cpu/x86/mtrr.h b/src/include/cpu/x86/mtrr.h
index f1e067a26b..dde9a2888b 100644
--- a/src/include/cpu/x86/mtrr.h
+++ b/src/include/cpu/x86/mtrr.h
@@ -1,6 +1,8 @@
#ifndef CPU_X86_MTRR_H
#define CPU_X86_MTRR_H
+#include <commonlib/helpers.h>
+
/* These are the region types */
#define MTRR_TYPE_UNCACHEABLE 0
#define MTRR_TYPE_WRCOMB 1
@@ -152,12 +154,20 @@ static inline unsigned int fls(unsigned int x)
to get a power of 2 again, for a single MTRR. */
#define CAR_END (CONFIG_DCACHE_RAM_BASE + CONFIG_DCACHE_RAM_SIZE)
#if CAR_END > OPTIMAL_CACHE_ROM_BASE
-# define CACHE_ROM_SIZE _ALIGN_DOWN_POW2(_FROM_4G_TOP(CAR_END))
+# define CAR_CACHE_ROM_SIZE _ALIGN_DOWN_POW2(_FROM_4G_TOP(CAR_END))
#else
-# define CACHE_ROM_SIZE OPTIMAL_CACHE_ROM_SIZE
+# define CAR_CACHE_ROM_SIZE OPTIMAL_CACHE_ROM_SIZE
+#endif
+#if ((CAR_CACHE_ROM_SIZE & (CAR_CACHE_ROM_SIZE - 1)) != 0)
+# error "CAR CACHE_ROM_SIZE is not a power of 2, _POW2_MASK needs refinement."
#endif
-#if ((CACHE_ROM_SIZE & (CACHE_ROM_SIZE - 1)) != 0)
-# error "CACHE_ROM_SIZE is not a power of 2, _POW2_MASK needs refinement."
+
+/* Last but not least, most (if not all) chipsets have MMIO
+ between 0xfe000000 and 0xff000000, so limit to 16MiB. */
+#if CAR_CACHE_ROM_SIZE >= 16 * MiB
+# define CACHE_ROM_SIZE (16 * MiB)
+#else
+# define CACHE_ROM_SIZE CAR_CACHE_ROM_SIZE
#endif
#define CACHE_ROM_BASE _FROM_4G_TOP(CACHE_ROM_SIZE)