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

[Murali Karicheri]

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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