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The current K8 stack preservation code in disable_car() works by chance,

Browse source 
but that's not something we should rely on.

The new code is entirely rewritten, fixes a few missing constraints in
the asm and should be a lot more readable. However, the generated code
is NOT identical. The old code was broken because of the missing ecx
clobber constraint and it did not copy the stack back (ecx was zero at
the beginning of the copy-back loop and so the loop executed exactly
zero times).
So this is a genuine bug fix.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

Ron writes:
wow! nice catch!

Acked-by: Ronald G. Minnich <rminnich@gmail.com>

We also need disable_car_and_halt, which only disables car and halts,
for the APs (i.e. no need to copy stack back)


git-svn-id: svn://coreboot.org/repository/coreboot-v3@858 f3766cd6-281f-0410-b1cd-43a5c92072e9
This commit is contained in:
Carl-Daniel Hailfinger 2008-09-05 10:29:33 +00:00
parent 49e1879723
commit ade1cd1f11
1 changed files with 22 additions and 11 deletions
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33
arch/x86/amd/k8/stage1.c
View file

@ -34,20 +34,31 @@
*/ */
void disable_car(void) void disable_car(void)
{ {
/* OK, here is the theory: we should be able to copy
* the data back over itself, and the wbinvd should then
* flush to memory. Let's see.
*/
/* nope.
__asm__ __volatile__("cld; rep movsl" ::"D" (CONFIG_CARBASE), "S" (CONFIG_CARBASE), "c" (CONFIG_CARSIZE/4): "memory");
*/
/* call the inlined function */ /* call the inlined function */
disable_cache_as_ram(); disable_cache_as_ram();
/* copy it down, wbinvd, copy it back? */ /* The BKDG says that a WBINVD will not flush CAR to RAM (because the
__asm__ __volatile__("cld; rep movsl" ::"D" (0x88000), "S" (CONFIG_CARBASE), "c" (CONFIG_CARSIZE/4): "memory"); * cache tags are not dirty).
__asm__ __volatile__ ("wbinvd\n"); * Solution:
__asm__ __volatile__("cld; rep movsl" ::"D" (CONFIG_CARBASE), "S" (0x88000), "c" (CONFIG_CARSIZE/4): "memory"); * - Two subsequent memcpy in the same inline asm block, one from stack
* to backup, one from backup to stack.
* The solution for geode of using a inline asm memcpy of the stack
* onto itself will not mark the cache tags as dirty on K8.
*/
__asm__ __volatile__(
" movl %[carbase], %%esi \n"
" movl %[backuplocation], %%edi \n"
" movl %[carsizequads], %%ecx \n"
" cld \n"
" rep movsl \n"
" wbinvd \n"
" movl %[backuplocation], %%esi \n"
" movl %[carbase], %%edi \n"
" movl %[carsizequads], %%ecx \n"
" rep movsl \n"
:: [carbase] "i" (CONFIG_CARBASE), [backuplocation] "i" (0x88000),
[carsizequads] "i" (CONFIG_CARSIZE/4)
: "memory", "%edi", "%esi", "%ecx");
banner(BIOS_DEBUG, "Disable_car: done wbinvd"); banner(BIOS_DEBUG, "Disable_car: done wbinvd");
banner(BIOS_DEBUG, "disable_car: done"); banner(BIOS_DEBUG, "disable_car: done");
} }