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

[Murali Karicheri]

On 08/14/2015 05:56 PM, Russell King - ARM Linux wrote:
> On Fri, Aug 14, 2015 at 05:55:09PM -0400, Murali Karicheri wrote:
>> On 08/14/2015 10:20 AM, Lucas Stach wrote:
>>> Hi Russell,
>>>
>>> Am Freitag, den 14.08.2015, 15:09 +0100 schrieb Russell King - ARM
>>> Linux:
>>>
>>> [...]
>>>
>>>>
>>>> What causes the abort?  We shouldn't be adding hacks like this to the
>>>> kernel without having the full picture...
>>>>
>>>
>>> some of the issues with tracking down such imprecise external aborts are
>>> due to the fact that we only enable the signaling of those aborts on
>>> entering the user-space. So the first schedule() crashes on the previous
>>> dangling abort.
>>>
>>> I'm carrying this patch locally to enable imprecise aborts much earlier
>>> in the boot process. I think it has already been on the list some times,
>>> but apparently it has fallen through the cracks. If you agree that this
>>> is the right thing to do I can do a proper repost.
>> Lucas,
>>
>> Would you mind sharing the code? Does that help in root causing where it
>> actually happens? I have spend considerable time debugging this, but so far
>> not successful.
>
> If you look below, Lucas provided the patch.
Oops! Thanks

Murali

>
>>
>> Murali
>>>
>>> Regards,
>>> Lucas
>>>
>>> ---------------------->8---------------------------------------------
>>> >From bb9117d94cc2f1061dc364f42c446ccd9191e869 Mon Sep 17 00:00:00 2001
>>> From: Lucas Stach <l.stach at pengutronix.de>
>>> Date: Thu, 19 Feb 2015 18:12:50 +0100
>>> Subject: [PATCH] ARM: Add imprecise abort enable/disable macro
>>>
>>> This patch adds imprecise abort enable/disable macros.
>>> It also enables imprecise aborts when starting kernel.
>>>
>>> Changes in v2:
>>> Only ARMv6 and later have CPSR.A bit. On earlier CPUs,
>>> and ARMv7M this should be a no-op.
>>>
>>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier at st.com>
>>> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
>>> ---
>>> lst: rebased on v3.19
>>> ---
>>>   arch/arm/include/asm/irqflags.h | 10 ++++++++++
>>>   arch/arm/kernel/smp.c           |  1 +
>>>   arch/arm/kernel/traps.c         |  4 ++++
>>>   3 files changed, 15 insertions(+)
>>>
>>> diff --git a/arch/arm/include/asm/irqflags.h
>>> b/arch/arm/include/asm/irqflags.h
>>> index 3b763d6652a0..8301f875564e 100644
>>> --- a/arch/arm/include/asm/irqflags.h
>>> +++ b/arch/arm/include/asm/irqflags.h
>>> @@ -51,6 +51,14 @@ static inline void arch_local_irq_disable(void)
>>>
>>>   #define local_fiq_enable()  __asm__("cpsie f   @ __stf" : : : "memory",
>>> "cc")
>>>   #define local_fiq_disable() __asm__("cpsid f   @ __clf" : : : "memory",
>>> "cc")
>>> +
>>> +#ifndef CONFIG_CPU_V7M
>>> +#define local_abt_enable()  __asm__("cpsie a   @ __sta" : : : "memory",
>>> "cc")
>>> +#define local_abt_disable() __asm__("cpsid a   @ __cla" : : : "memory",
>>> "cc")
>>> +#else
>>> +#define local_abt_enable()     do { } while (0)
>>> +#define local_abt_disable()    do { } while (0)
>>> +#endif
>>>   #else
>>>
>>>   /*
>>> @@ -130,6 +138,8 @@ static inline void arch_local_irq_disable(void)
>>>          : "memory", "cc");                                      \
>>>          })
>>>
>>> +#define local_abt_enable()     do { } while (0)
>>> +#define local_abt_disable()    do { } while (0)
>>>   #endif
>>>
>>>   /*
>>> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
>>> index 86ef244c5a24..7b6b93cabef4 100644
>>> --- a/arch/arm/kernel/smp.c
>>> +++ b/arch/arm/kernel/smp.c
>>> @@ -378,6 +378,7 @@ asmlinkage void secondary_start_kernel(void)
>>>
>>>          local_irq_enable();
>>>          local_fiq_enable();
>>> +       local_abt_enable();
>>>
>>>          /*
>>>           * OK, it's off to the idle thread for us
>>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
>>> index 788e23fe64d8..466726ba9bdb 100644
>>> --- a/arch/arm/kernel/traps.c
>>> +++ b/arch/arm/kernel/traps.c
>>> @@ -881,6 +881,10 @@ void __init early_trap_init(void *vectors_base)
>>>
>>>          flush_icache_range(vectors, vectors + PAGE_SIZE * 2);
>>>          modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
>>> +
>>> +       /* Enable imprecise aborts */
>>> +       local_abt_enable();
>>> +
>>>   #else /* ifndef CONFIG_CPU_V7M */
>>>          /*
>>>           * on V7-M there is no need to copy the vector table to a
>>> dedicated
>>>
>>
>>
>> --
>> Murali Karicheri
>> Linux Kernel, Keystone
>


-- 
Murali Karicheri
Linux Kernel, Keystone