New patch to review for coreboot: 48c4b9a cmos post: Guard with spinlock

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/4227

-gerrit

commit 48c4b9ab720a46e6c587a7fc88347acf53ee3f89
Author: Duncan Laurie 
Date:   Mon Jun 10 09:53:33 2013 -0700

cmos post: Guard with spinlock

The CMOS post code storage mechanism does back-to-back
    CMOS reads and writes that may be interleaved during
    CPU bringup, leading to corruption of the log or of other
    parts of CMOS.

Change-Id: I704813cc917a659fe034b71c2ff9eb9b80f7c949
    Signed-off-by: Duncan Laurie 
    Reviewed-on: https://gerrit.chromium.org/gerrit/58102
    Reviewed-by: Aaron Durbin 
---
 src/arch/x86/include/arch/smp/spinlock.h | 14 ++++++++++++++
 src/console/post.c                       | 15 ++++++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/arch/x86/include/arch/smp/spinlock.h b/src/arch/x86/include/arch/smp/spinlock.h
index 5c1dd94..32be2f2 100644
--- a/src/arch/x86/include/arch/smp/spinlock.h
+++ b/src/arch/x86/include/arch/smp/spinlock.h
@@ -1,6 +1,8 @@
 #ifndef ARCH_SMP_SPINLOCK_H
 #define ARCH_SMP_SPINLOCK_H

+#ifndef __PRE_RAM__
+
 /*
  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  */
@@ -61,4 +63,16 @@ static inline __attribute__((always_inline)) void cpu_relax(void)
    __asm__ __volatile__("rep;nop": : :"memory");
 }

+#else /* !__PRE_RAM__ */
+
+#define DECLARE_SPIN_LOCK(x)
+#define barrier()		do {} while(0)
+#define spin_is_locked(lock)	0
+#define spin_unlock_wait(lock)	do {} while(0)
+#define spin_lock(lock)		do {} while(0)
+#define spin_unlock(lock)	do {} while(0)
+#define cpu_relax()		do {} while(0)
+
+#endif /* !__PRE_RAM__ */
+
 #endif /* ARCH_SMP_SPINLOCK_H */
diff --git a/src/console/post.c b/src/console/post.c
index f55683e..11c631d 100644
--- a/src/console/post.c
+++ b/src/console/post.c
@@ -23,6 +23,7 @@
 #include <console/console.h>
 #if CONFIG_CMOS_POST
 #include <pc80/mc146818rtc.h>
+#include <smp/spinlock.h>
 #endif
 #include <elog.h>

@@ -44,10 +45,14 @@ void __attribute__((weak)) mainboard_post(uint8_t value)

#if CONFIG_CMOS_POST

+DECLARE_SPIN_LOCK(cmos_post_lock)
+
 #if !defined(__PRE_RAM__)
 void cmos_post_log(void)
 {
-	u8 code;
+	u8 code = 0;
+
+	spin_lock(&cmos_post_lock);

/* Get post code from other bank */
    switch (cmos_read(CMOS_POST_BANK_OFFSET)) {
@@ -57,10 +62,10 @@ void cmos_post_log(void)
    case CMOS_POST_BANK_1_MAGIC:
    	code = cmos_read(CMOS_POST_BANK_0_OFFSET);
    	break;
-	default:
-		return;
    }

+	spin_unlock(&cmos_post_lock);
+
    /* Check last post code in previous boot against normal list */
    switch (code) {
    case POST_OS_BOOT:
@@ -80,6 +85,8 @@ void cmos_post_log(void)

static void cmos_post_code(u8 value)
 {
+	spin_lock(&cmos_post_lock);
+
    switch (cmos_read(CMOS_POST_BANK_OFFSET)) {
    case CMOS_POST_BANK_0_MAGIC:
    	cmos_write(value, CMOS_POST_BANK_0_OFFSET);
@@ -88,6 +95,8 @@ static void cmos_post_code(u8 value)
    	cmos_write(value, CMOS_POST_BANK_1_OFFSET);
    	break;
    }
+
+	spin_unlock(&cmos_post_lock);
 }
 #endif /* CONFIG_CMOS_POST */