ARC: Add option to control SCM

Shared Cache Memory (SCM) is L2 cache used in ARCv3.

Sometimes we don't want to have it enabled (to test performance
change), so need to have an option to control it.

Please note that this option works only for ARCv3 SCM, because in
ARCv2 L2 cache is enabled by default and cannot be disabled in such
easy way.

Signed-off-by: Vladimir Isaev <isaev@synopsys.com>

Author: Vladimir Isaev

arch/arc/Kconfig

@@ -259,6 +259,11 @@ config ARC_CACHE_PAGES
 	  Note that Global I/D ENABLE + Per Page DISABLE works but corollary
 	  Global DISABLE + Per Page ENABLE won't work
 
+config ARC_HAS_SCM
+	bool "Use Shared Cache Memory"
+	depends on ISA_ARCV3
+	default y
+
 config ARC_CACHE_VIPT_ALIASING
 	bool "Support VIPT Aliasing D$"
 	depends on ARC_HAS_DCACHE && ISA_ARCOMPACT

arch/arc/mm/cache-arcv3.c

@@ -8,7 +8,7 @@
 #include <asm/cacheflush.h>
 #include <asm/setup.h>
 
-int l2_enable = 1;
+int l2_enable = IS_ENABLED(CONFIG_ARC_HAS_SCM);
 
 static struct cpuinfo_arc_cache {
 	unsigned int sz_k, line_len, colors;