[coreboot-gerrit] Change in coreboot[master]: arch/x86/exit_car.S: Make sure _cbmem_top_ptr hits dram

[Arthur Heymans (Code Review)]

Arthur Heymans has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/37212 )

Change subject: arch/x86/exit_car.S: Make sure _cbmem_top_ptr hits dram
......................................................................

arch/x86/exit_car.S: Make sure _cbmem_top_ptr hits dram

INVD is called below so if postcar is running in a cached environment
it needs to happen.

NOTE: postcar cannot execute in a cached environment if clflush is not
supported!

Change-Id: I37681ee1f1d2ae5f9dd824b5baf7b23b2883b1dc
Signed-off-by: Arthur Heymans 
---
M src/arch/x86/exit_car.S
1 file changed, 7 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/12/37212/1

diff --git a/src/arch/x86/exit_car.S b/src/arch/x86/exit_car.S
index 8c28784..ceb0321 100644
--- a/src/arch/x86/exit_car.S
+++ b/src/arch/x86/exit_car.S
@@ -38,7 +38,14 @@
    movl	4(%esp), %eax
    movl	%eax, _cbmem_top_ptr
 #endif
+	/* Make sure _cbmem_top_ptr hits dram before invd */
+	movl	$1, %eax
+	cpuid
+	btl	$19, %edx
+	jz	skip_clflush
+	clflush	_cbmem_top_ptr

+skip_clflush:
    /* chipset_teardown_car() is expected to disable cache-as-ram. */
    call	chipset_teardown_car