[PATCH 1/3] arm64: Track system support for mixed endian EL0

["Suzuki K. Poulose" <suzuki.poulose@arm.com>]

From: "Suzuki K. Poulose" <suzuki.poulose@arm.com>

This patch keeps track of the mixed endian EL0 support across
the system and provides helper functions to export it. The status
is a boolean indicating whether all the CPUs on the system supports
mixed endian at EL0.

Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
---
 arch/arm64/include/asm/cpufeature.h |   10 ++++++++++
 arch/arm64/kernel/cpuinfo.c         |   22 ++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 07547cc..c7f68d1 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -26,6 +26,9 @@
 
 #define ARM64_NCAPS				2
 
+#define ID_AA64MMFR0_EL1_BigEndEL0	(0x1UL << 16)
+#define ID_AA64MMFR0_EL1_BigEnd		(0x1UL << 8)
+
 #ifndef __ASSEMBLY__
 
 extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
@@ -51,7 +54,14 @@ static inline void cpus_set_cap(unsigned int num)
 		__set_bit(num, cpu_hwcaps);
 }
 
+static inline bool id_aa64mmfr0_mixed_endian_el0(unsigned long mmfr0)
+{
+	return !!(mmfr0 & (ID_AA64MMFR0_EL1_BigEndEL0 | ID_AA64MMFR0_EL1_BigEnd));
+}
+
 void check_local_cpu_errata(void);
+bool system_supports_mixed_endian_el0(void);
+bool cpu_supports_mixed_endian_el0(void);
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 07d435c..b6d1135 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -35,6 +35,7 @@
  */
 DEFINE_PER_CPU(struct cpuinfo_arm64, cpu_data);
 static struct cpuinfo_arm64 boot_cpu_data;
+static bool mixed_endian_el0 = true;
 
 static char *icache_policy_str[] = {
 	[ICACHE_POLICY_RESERVED] = "RESERVED/UNKNOWN",
@@ -68,6 +69,26 @@ static void cpuinfo_detect_icache_policy(struct cpuinfo_arm64 *info)
 	pr_info("Detected %s I-cache on CPU%d\n", icache_policy_str[l1ip], cpu);
 }
 
+bool cpu_supports_mixed_endian_el0(void)
+{
+	return id_aa64mmfr0_mixed_endian_el0(read_cpuid(ID_AA64MMFR0_EL1));
+}
+
+bool system_supports_mixed_endian_el0(void)
+{
+	return mixed_endian_el0;
+}
+
+static void update_mixed_endian_el0_support(struct cpuinfo_arm64 *info)
+{
+	mixed_endian_el0 &= id_aa64mmfr0_mixed_endian_el0(info->reg_id_aa64mmfr0);
+}
+
+static void update_cpu_features(struct cpuinfo_arm64 *info)
+{
+	update_mixed_endian_el0_support(info);
+}
+
 static int check_reg_mask(char *name, u64 mask, u64 boot, u64 cur, int cpu)
 {
 	if ((boot & mask) == (cur & mask))
@@ -215,6 +236,7 @@ static void __cpuinfo_store_cpu(struct cpuinfo_arm64 *info)
 	cpuinfo_detect_icache_policy(info);
 
 	check_local_cpu_errata();
+	update_cpu_features(info);
 }
 
 void cpuinfo_store_cpu(void)
-- 
1.7.9.5