ARM: 7855/1: Add check for Cortex-A15 errata 798181 ECO

The work-around for A15 errata 798181 is not needed if appropriate ECO
fixes have been applied to r3p2 and earlier core revisions. This can be
checked by reading REVIDR register bits 4 and 9. If only bit 4 is set,
then the IPI broadcast can be skipped.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 36 insertions, 2 deletions

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 0e1e2b3afa45..a4852dea088b 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -599,6 +599,8 @@ static void __init setup_processor(void)
 	elf_hwcap &= ~(HWCAP_THUMB | HWCAP_IDIVT);
 #endif
 
+	erratum_a15_798181_init();
+
 	feat_v6_fixup();
 
 	cacheid_init();
diff --git a/arch/arm/kernel/smp_tlb.c b/arch/arm/kernel/smp_tlb.c
index 83ccca303df8..95d063620b76 100644
--- a/arch/arm/kernel/smp_tlb.c
+++ b/arch/arm/kernel/smp_tlb.c
@@ -70,6 +70,40 @@ static inline void ipi_flush_bp_all(void *ignored)
 	local_flush_bp_all();
 }
 
+#ifdef CONFIG_ARM_ERRATA_798181
+bool (*erratum_a15_798181_handler)(void);
+
+static bool erratum_a15_798181_partial(void)
+{
+	asm("mcr p15, 0, %0, c8, c3, 1" : : "r" (0));
+	dsb(ish);
+	return false;
+}
+
+static bool erratum_a15_798181_broadcast(void)
+{
+	asm("mcr p15, 0, %0, c8, c3, 1" : : "r" (0));
+	dsb(ish);
+	return true;
+}
+
+void erratum_a15_798181_init(void)
+{
+	unsigned int midr = read_cpuid_id();
+	unsigned int revidr = read_cpuid(CPUID_REVIDR);
+
+	/* Cortex-A15 r0p0..r3p2 w/o ECO fix affected */
+	if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2 ||
+	    (revidr & 0x210) == 0x210) {
+		return;
+	}
+	if (revidr & 0x10)
+		erratum_a15_798181_handler = erratum_a15_798181_partial;
+	else
+		erratum_a15_798181_handler = erratum_a15_798181_broadcast;
+}
+#endif
+
 static void ipi_flush_tlb_a15_erratum(void *arg)
 {
 	dmb();
@@ -80,7 +114,6 @@ static void broadcast_tlb_a15_erratum(void)
 	if (!erratum_a15_798181())
 		return;
 
-	dummy_flush_tlb_a15_erratum();
 	smp_call_function(ipi_flush_tlb_a15_erratum, NULL, 1);
 }
 
@@ -92,7 +125,6 @@ static void broadcast_tlb_mm_a15_erratum(struct mm_struct *mm)
 	if (!erratum_a15_798181())
 		return;
 
-	dummy_flush_tlb_a15_erratum();
 	this_cpu = get_cpu();
 	a15_erratum_get_cpumask(this_cpu, mm, &mask);
 	smp_call_function_many(&mask, ipi_flush_tlb_a15_erratum, NULL, 1);