1 files changed, 30 insertions, 4 deletions

diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c
index 5ab5fa8c1d82..505fecad4684 100644
--- a/arch/mips/mm/sc-mips.c
+++ b/arch/mips/mm/sc-mips.c
@@ -57,6 +57,34 @@ static struct bcache_ops mips_sc_ops = {
         .bc_inv = mips_sc_inv
 };
 
+/*
+ * Check if the L2 cache controller is activated on a particular platform.
+ * MTI's L2 controller and the L2 cache controller of Broadcom's BMIPS
+ * cores both use c0_config2's bit 12 as "L2 Bypass" bit, that is the
+ * cache being disabled.  However there is no guarantee for this to be
+ * true on all platforms.  In an act of stupidity the spec defined bits
+ * 12..15 as implementation defined so below function will eventually have
+ * to be replaced by a platform specific probe.
+ */
+static inline int mips_sc_is_activated(struct cpuinfo_mips *c)
+{
+        /* Check the bypass bit (L2B) */
+        switch (c->cputype) {
+        case CPU_34K:
+        case CPU_74K:
+        case CPU_1004K:
+        case CPU_BMIPS5000:
+                if (config2 & (1 << 12))
+                        return 0;
+        }
+
+        tmp = (config2 >> 4) & 0x0f;
+        if (0 < tmp && tmp <= 7)
+                c->scache.linesz = 2 << tmp;
+        else
+                return 0;
+}
+
 static inline int __init mips_sc_probe(void)
 {
         struct cpuinfo_mips *c = &current_cpu_data;
@@ -79,10 +107,8 @@ static inline int __init mips_sc_probe(void)
                 return 0;
 
         config2 = read_c0_config2();
-        tmp = (config2 >> 4) & 0x0f;
-        if (0 < tmp && tmp <= 7)
-                c->scache.linesz = 2 << tmp;
-        else
+
+        if (!mips_sc_is_activated(c))
                 return 0;
 
         tmp = (config2 >> 8) & 0x0f;