ARM: keystone: add a work around to handle external abort

Currently on some devices, an async external abort happens first time
exception handlers are enabled in kernel before switching to user space.
This patch add a workaround to handle this once and allow any subsequent
faults to be caught by the handler.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>

diff --git a/arch/arm/mach-keystone/keystone.c b/arch/arm/mach-keystone/keystone.c
index 05f220211fcfb92d7ffc666ff4aac3205a014009..d831ca983bcc41769d341f609f4c677ad1a5d636 100644 (file)
--- a/arch/arm/mach-keystone/keystone.c
+++ b/arch/arm/mach-keystone/keystone.c
@@ -28,6 +28,7 @@
 #include <linux/irqchip.h>
 #include <linux/platform_data/davinci-clock.h>
 #include <linux/reboot.h>
+#include <linux/signal.h>
 
 #include <asm/setup.h>
 #include <asm/smp_plat.h>
@@ -83,6 +84,24 @@ static bool is_coherent(struct device *dev)
        return false;
 }
 
+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 seems to be a spurious one
+        * happening on some devices and we add this work around to handle
+        * this first time when kernel switch to handle user space
+        */
+       if (ignore_first) {
+               ignore_first = false;
+               return 0;
+       }
+
+       /* Subsequent ones should be handled as fault */
+       return 1;
+}
+
 static int keystone_platform_notifier(struct notifier_block *nb,
                                      unsigned long event, void *_dev)
 {
@@ -118,6 +137,13 @@ static void __init keystone_init(void)
 
        keystone_pm_runtime_init();
        of_platform_populate(NULL, keystone_dt_match_table, NULL, NULL);
+
+       /*
+        * Add a one time exception handler to catch asynchronous external
+        * abort when transitioning to use space
+        */
+       hook_fault_code(17, keystone_async_ext_abort_fault, SIGBUS, 0,
+                       "async external abort handler");
 }
 
 #define L2_INTERN_ASYNC_ERROR  BIT(30)