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

From: Murali Karicheri
Date: Mon Aug 17 2015 - 10:11:42 EST


On 08/14/2015 10:11 AM, Lucas Stach wrote:
Am Freitag, den 14.08.2015, 10:04 -0400 schrieb Murali Karicheri:
On 08/11/2015 03:13 PM, Murali Karicheri wrote:
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@xxxxxx>
---
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)

Can this be applied if it looks good?

The keystone PCIe host driver already hooks the same fault code. Those
hooks are no chain, but a simple pointer, so one of those handlers is
going to loose out.

This likely isn't what you intended.
You are right. I will try to debug this further based on your patch and as per RMK's suggestion.

Thanks and regards,

Murali

Regards,
Lucas



--
Murali Karicheri
Linux Kernel, Keystone
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