ARM: 7789/1: Do not run dummy_flush_tlb_a15_erratum() on non-Cortex-A15

Commit 93dc688 (ARM: 7684/1: errata: Workaround for Cortex-A15 erratum 798181 (TLBI/DSB operations)) causes the following undefined instruction error on a mx53 (Cortex-A8):

Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
CPU: 0 PID: 275 Comm: modprobe Not tainted 3.11.0-rc2-next-20130722-00009-g9b0f371 #881
task: df46cc00 ti: df48e000 task.ti: df48e000
PC is at check_and_switch_context+0x17c/0x4d0
LR is at check_and_switch_context+0xdc/0x4d0

This problem happens because check_and_switch_context() calls dummy_flush_tlb_a15_erratum() without checking if we are really running on a Cortex-A15 or not.

To avoid this issue, only call dummy_flush_tlb_a15_erratum() inside
check_and_switch_context() if erratum_a15_798181() returns true, which means that we are really running on a Cortex-A15.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/tlbflush.h

@@ -443,7 +443,18 @@ static inline void local_flush_bp_all(void)
 		isb();
 }
 
+#include <asm/cputype.h>
 #ifdef CONFIG_ARM_ERRATA_798181
+static inline int erratum_a15_798181(void)
+{
+	unsigned int midr = read_cpuid_id();
+
+	/* Cortex-A15 r0p0..r3p2 affected */
+	if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2)
+		return 0;
+	return 1;
+}
+
 static inline void dummy_flush_tlb_a15_erratum(void)
 {
 	/*
@@ -453,6 +464,11 @@ static inline void dummy_flush_tlb_a15_erratum(void)
 	dsb();
 }
 #else
+static inline int erratum_a15_798181(void)
+{
+	return 0;
+}
+
 static inline void dummy_flush_tlb_a15_erratum(void)
 {
 }

arch/arm/kernel/smp_tlb.c

@@ -70,23 +70,6 @@ static inline void ipi_flush_bp_all(void *ignored)
 	local_flush_bp_all();
 }
 
-#ifdef CONFIG_ARM_ERRATA_798181
-static int erratum_a15_798181(void)
-{
-	unsigned int midr = read_cpuid_id();
-
-	/* Cortex-A15 r0p0..r3p2 affected */
-	if ((midr & 0xff0ffff0) != 0x410fc0f0 || midr > 0x413fc0f2)
-		return 0;
-	return 1;
-}
-#else
-static int erratum_a15_798181(void)
-{
-	return 0;
-}
-#endif
-
 static void ipi_flush_tlb_a15_erratum(void *arg)
 {
 	dmb();

arch/arm/mm/context.c

@@ -245,7 +245,8 @@ void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
 	if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
 		local_flush_bp_all();
 		local_flush_tlb_all();
-		dummy_flush_tlb_a15_erratum();
+		if (erratum_a15_798181())
+			dummy_flush_tlb_a15_erratum();
 	}
 
 	atomic64_set(&per_cpu(active_asids, cpu), asid);