ARM: l2x0: only write to debug registers on PL310

PL310 errata #588369 and #727915 requires writes to the debug registers
of the cache controller to workaround known problems. Writing these
registers on L220 may cause deadlock, so ensure that we only perform
this operation when we identify a PL310 at probe time.

Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
index 971d527..db7bcc0 100644
--- a/arch/arm/mm/cache-l2x0.c
+++ b/arch/arm/mm/cache-l2x0.c
@@ -81,10 +81,13 @@
 }
 
 #if defined(CONFIG_PL310_ERRATA_588369) || defined(CONFIG_PL310_ERRATA_727915)
+static inline void debug_writel(unsigned long val)
+{
+	if (outer_cache.set_debug)
+		outer_cache.set_debug(val);
+}
 
-#define debug_writel(val)	outer_cache.set_debug(val)
-
-static void l2x0_set_debug(unsigned long val)
+static void pl310_set_debug(unsigned long val)
 {
 	writel_relaxed(val, l2x0_base + L2X0_DEBUG_CTRL);
 }
@@ -94,7 +97,7 @@
 {
 }
 
-#define l2x0_set_debug	NULL
+#define pl310_set_debug	NULL
 #endif
 
 #ifdef CONFIG_PL310_ERRATA_588369
@@ -331,6 +334,7 @@
 		/* Unmapped register. */
 		sync_reg_offset = L2X0_DUMMY_REG;
 #endif
+		outer_cache.set_debug = pl310_set_debug;
 		break;
 	case L2X0_CACHE_ID_PART_L210:
 		ways = (aux >> 13) & 0xf;
@@ -379,7 +383,6 @@
 	outer_cache.flush_all = l2x0_flush_all;
 	outer_cache.inv_all = l2x0_inv_all;
 	outer_cache.disable = l2x0_disable;
-	outer_cache.set_debug = l2x0_set_debug;
 
 	printk(KERN_INFO "%s cache controller enabled\n", type);
 	printk(KERN_INFO "l2x0: %d ways, CACHE_ID 0x%08x, AUX_CTRL 0x%08x, Cache size: %d B\n",