arm64: avoid -Woverride-init warning

The icache_policy_str[] definition causes a warning when extra
warning flags are enabled:

arch/arm64/kernel/cpuinfo.c:38:26: warning: initialized field overwritten [-Woverride-init]
   38 |  [ICACHE_POLICY_VIPT]  = "VIPT",
      |                          ^~~~~~
arch/arm64/kernel/cpuinfo.c:38:26: note: (near initialization for 'icache_policy_str[2]')
arch/arm64/kernel/cpuinfo.c:39:26: warning: initialized field overwritten [-Woverride-init]
   39 |  [ICACHE_POLICY_PIPT]  = "PIPT",
      |                          ^~~~~~
arch/arm64/kernel/cpuinfo.c:39:26: note: (near initialization for 'icache_policy_str[3]')
arch/arm64/kernel/cpuinfo.c:40:27: warning: initialized field overwritten [-Woverride-init]
   40 |  [ICACHE_POLICY_VPIPT]  = "VPIPT",
      |                           ^~~~~~~
arch/arm64/kernel/cpuinfo.c:40:27: note: (near initialization for 'icache_policy_str[0]')

There is no real need for the default initializer here, as printing a
NULL string is harmless. Rewrite the logic to have an explicit
reserved value for the only one that uses the default value.

This partially reverts the commit that removed ICACHE_POLICY_AIVIVT.

Fixes: 155433cb ("arm64: cache: Remove support for ASID-tagged VIVT I-caches")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201026193807.3816388-1-arnd@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/cache.h

@@ -24,6 +24,7 @@
 #define CTR_L1IP(ctr)		(((ctr) >> CTR_L1IP_SHIFT) & CTR_L1IP_MASK)
 
 #define ICACHE_POLICY_VPIPT	0
+#define ICACHE_POLICY_RESERVED	1
 #define ICACHE_POLICY_VIPT	2
 #define ICACHE_POLICY_PIPT	3
 

arch/arm64/kernel/cpuinfo.c

@@ -34,10 +34,10 @@ DEFINE_PER_CPU(struct cpuinfo_arm64, cpu_data);
 static struct cpuinfo_arm64 boot_cpu_data;
 
 static const char *icache_policy_str[] = {
-	[0 ... ICACHE_POLICY_PIPT]	= "RESERVED/UNKNOWN",
+	[ICACHE_POLICY_VPIPT]		= "VPIPT",
+	[ICACHE_POLICY_RESERVED]	= "RESERVED/UNKNOWN",
 	[ICACHE_POLICY_VIPT]		= "VIPT",
 	[ICACHE_POLICY_PIPT]		= "PIPT",
-	[ICACHE_POLICY_VPIPT]		= "VPIPT",
 };
 
 unsigned long __icache_flags;
@@ -334,10 +334,11 @@ static void cpuinfo_detect_icache_policy(struct cpuinfo_arm64 *info)
 	case ICACHE_POLICY_VPIPT:
 		set_bit(ICACHEF_VPIPT, &__icache_flags);
 		break;
-	default:
+	case ICACHE_POLICY_RESERVED:
 	case ICACHE_POLICY_VIPT:
 		/* Assume aliasing */
 		set_bit(ICACHEF_ALIASING, &__icache_flags);
+		break;
 	}
 
 	pr_info("Detected %s I-cache on CPU%d\n", icache_policy_str[l1ip], cpu);