[PATCH] arm: mm: fault: check ADFSR in case of abort

[Wiebe, Wladislav (Nokia - DE/Ulm)]

When running into situations like:
"Unhandled fault: synchronous external abort (0x210) at 0xXXX"
or
"Unhandled prefetch abort: synchronous external abort (0x210) at 0xXXX"
it is useful to know the content of ADFSR (Auxiliary Data Fault Status
Register) to indicate an ECC double-bit error in L1 or L2 cache.

Refer to:
Cortex-A15 Technical Reference Manual, Revision: r2p1
[6.4.8. Error Correction Code]

Signed-off-by: Wladislav Wiebe <wladislav.wiebe@xxxxxxxxx>
---
 arch/arm/mm/fault.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 3232afb6fdc0..5e240deb6ed6 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -547,6 +547,22 @@ hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *)
 	fsr_info[nr].name = name;
 }
 
+/*
+ * Check for ECC double-bit errors in Auxiliary Data Fault Status Register
+ */
+static void check_adfsr_for_ecc(void)
+{
+	u32 adfsr = 0;
+
+	asm("mrc p15, 0, %0, c5, c1, 0" : "=r" (adfsr));
+
+	if (adfsr & (BIT(31) | BIT(23))) {
+		pr_alert("ADFSR status 0x%x indicates that an L1 or L2 cache\n"
+			 "ECC double-bit error occurred at some time.\n",
+			  adfsr);
+	}
+}
+
 /*
  * Dispatch a data abort to the relevant handler.
  */
@@ -559,6 +575,7 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 		return;
 
+	check_adfsr_for_ecc();
 	pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 		inf->name, fsr, addr);
 	show_pte(current->mm, addr);
@@ -593,6 +610,7 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
 	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 		return;
 
+	check_adfsr_for_ecc();
 	pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 		inf->name, ifsr, addr);
 
-- 
2.16.1