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

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Date:	Tue, 11 Aug 2015 15:13:29 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	<ssantosh@...nel.org>, <linux@....linux.org.uk>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] ARM: keystone: add a work around to handle asynchronous external abort

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@...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

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