arch/x86: Support "weak" BIST and timestamp save routines

Not all x86 architectures support the mm register set.  The default
routine that saves BIST in mm0 and a "weak" routine that saves the TSC
value in mm2:mm1.  Select the Kconfig value
BOOTBLOCK_SAVE_BIST_AND_TIMESTAMP to provide a replacement routine to
save the BIST and timestamp values.

TEST=Build and run on Amenia and Galileo Gen2.

Change-Id: I8119e74664ac3522c011767d424d441cd62545ce
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: https://review.coreboot.org/15126
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/arch/x86/Kconfig

@@ -133,6 +133,15 @@ config BOOTBLOCK_NORTHBRIDGE_INIT
 config BOOTBLOCK_RESETS
 	string
 
+config BOOTBLOCK_SAVE_BIST_AND_TIMESTAMP
+	bool
+	default n
+	help
+	  Select this value to provide a routine to save the BIST and timestamp
+	  values.  The default code places the BIST value in MM0 and the
+	  timestamp value in MM2:MM1.  Another file is necessary when the CPU
+	  does not support the MMx register set.
+
 config HAVE_CMOS_DEFAULT
 	def_bool n
 

src/arch/x86/bootblock_crt0.S

@@ -43,12 +43,28 @@ debug_spinloop:
 #endif
 
 bootblock_protected_mode_entry:
-	/* Save BIST result */
-	movd	%eax, %mm0
-	/* Save an early timestamp */
+
+	/* BIST result in eax */
+	movl	%eax, %ebx
+
+	/* Get an early timestamp */
 	rdtsc
+
+#if IS_ENABLED(CONFIG_BOOTBLOCK_SAVE_BIST_AND_TIMESTAMP)
+	lea	1f, %ebp
+
+	/* eax: Low 32-bits of timestamp
+	 * ebx: BIST result
+	 * ebp: return address
+	 * edx: High 32-bits of timestamp
+	 */
+	jmp	bootblock_save_bist_and_timestamp
+1:
+#else
+	movd	%ebx, %mm0
 	movd	%eax, %mm1
 	movd	%edx, %mm2
+#endif
 
 #if IS_ENABLED(CONFIG_SSE)
 enable_sse: