[PATCH] ARM: keystone: add a work around to handle asynchronous external abort

[Murali Karicheri]

Currently on some devices, an asynchronous external abort exception
happens during boot up when exception handlers are enabled in kernel
before switching to user space. This patch adds a workaround to handle
this once during boot. Many customers are already using this
with out any issues and is required to workaround the above issue.

Signed-off-by: Murali Karicheri <m-karicheri2 at ti.com>
---
 arch/arm/mach-keystone/keystone.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/arm/mach-keystone/keystone.c b/arch/arm/mach-keystone/keystone.c
index e2880105..c1d0fe5 100644
--- a/arch/arm/mach-keystone/keystone.c
+++ b/arch/arm/mach-keystone/keystone.c
@@ -15,6 +15,7 @@
 #include <linux/of_platform.h>
 #include <linux/of_address.h>
 #include <linux/memblock.h>
+#include <linux/signal.h>
 
 #include <asm/setup.h>
 #include <asm/mach/map.h>
@@ -52,6 +53,24 @@ static struct notifier_block platform_nb = {
 	.notifier_call = keystone_platform_notifier,
 };
 
+static bool ignore_first = true;
+static int keystone_async_ext_abort_fault(unsigned long addr, unsigned int fsr,
+					  struct pt_regs *regs)
+{
+	/*
+	 * if first time, ignore this as this is a asynchronous external abort
+	 * happening only some devices that couldn't be root caused and we add
+	 * this work around to handle this first time.
+	 */
+	if (ignore_first) {
+		ignore_first = false;
+		return 0;
+	}
+
+	/* Subsequent ones should be handled as fault */
+	return 1;
+}
+
 static void __init keystone_init(void)
 {
 	if (PHYS_OFFSET >= KEYSTONE_HIGH_PHYS_START) {
@@ -61,6 +80,13 @@ static void __init keystone_init(void)
 	}
 	keystone_pm_runtime_init();
 	of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
+
+	/*
+	 * Add a one time exception handler to catch asynchronous external
+	 * abort
+	 */
+	hook_fault_code(17, keystone_async_ext_abort_fault, SIGBUS, 0,
+			"async external abort handler");
 }
 
 static phys_addr_t keystone_virt_to_idmap(unsigned long x)
-- 
1.9.1