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

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Date:	Fri, 14 Aug 2015 10:04:41 -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: Re: [PATCH] ARM: keystone: add a work around to handle asynchronous
 external abort

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@...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)
>
Can this be applied if it looks good?

Murali

-- 
Murali Karicheri
Linux Kernel, Keystone
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