x86: provide consistent cbmem_top() for CONFIG_LATE_CBMEM_INIT
For x86 systems employing CONFIG_LATE_CBMEM_INIT, set_top_of_ram() is
called in ramstage to note the upper address of the 32-bit address
space. This in turn is consumed by cbmem. However, in this scenario
cbmem_top() cannot always be relied upon because get_top_of_ram()
doesn't return the same value provided to set_top_of_ram().
To fix the inconsistency in ramstage save the value passed in
to set_top_of_ram() and defer to it as the return value for
cbmem_top().
Change-Id: Ida796fb836c59b9776019e7f8b3f2cd71156f0e5
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/10313
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins)
diff --git a/src/arch/x86/boot/cbmem.c b/src/arch/x86/boot/cbmem.c
index 9ee5db4..f48e46a 100644
--- a/src/arch/x86/boot/cbmem.c
+++ b/src/arch/x86/boot/cbmem.c
@@ -34,10 +34,23 @@
/* Do nothing. Chipset may have implementation to save ramtop in NVRAM. */
}
+static void *ramtop_pointer;
+
void set_top_of_ram(uint64_t ramtop)
{
backup_top_of_ram(ramtop);
- cbmem_set_top((void*)(uintptr_t)ramtop);
+ ramtop_pointer = (void *)(uintptr_t)ramtop;
+ cbmem_set_top(ramtop_pointer);
+}
+
+static inline void *saved_ramtop(void)
+{
+ return ramtop_pointer;
+}
+#else
+static inline void *saved_ramtop(void)
+{
+ return NULL;
}
#endif /* !__PRE_RAM__ */
@@ -50,6 +63,11 @@
void *cbmem_top(void)
{
/* Top of cbmem is at lowest usable DRAM address below 4GiB. */
+ void *ptr = saved_ramtop();
+
+ if (ptr != NULL)
+ return ptr;
+
return (void *)get_top_of_ram();
}