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

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Date:	Tue, 18 Aug 2015 16:25:44 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	"santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com>
CC:	<ssantosh@...nel.org>, <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

Russell,

On 08/18/2015 04:13 AM, Russell King - ARM Linux wrote:
> On Mon, Aug 17, 2015 at 08:09:17PM -0700, santosh.shilimkar@...cle.com wrote:
>>  From the logs this seems to be mostly clock related issue for some
>> peripheral. If the bootloader clock enable all hack still exists,
>> may be you can try that out.
>>
>> Another way to debug this is to start disabling peripheral drivers
>> from the kernel 1 by 1 and see if the issue goes away.
>
> Highly unlikely to make any difference.  As the failure happens soo early
> with the patch applied, the kernel hasn't had much of a chance to touch
> the hardware - about the only things are the decompressor and the kernel
> touching the early console.  As they seem to be working, it suggests
> that's not the cause.
>
> It seems to be pointing towards something in the boot loader...
>
> Normally, uboot will hook itself into the vectors to report errors, but
> I wonder whether uboot enables asynchronous aborts while it's running.
> Don't forget to make sure that the aborts are disabled again prior to
> calling the kernel.
>
Thanks for your input.

The patch works now once I move the local_abort_enable() to later just 
before calling reserve_crashkernel() in setup_arch(). The abort handler 
gets called right after enabling it which means it has happened even 
before reaching here.

I have added the abort handler to u-boot code and I get the same abort 
which means the root cause is u-boot or ROM boot loader. I would try to 
debug if root cause is u-boot. If it is ROM boot loader, I will have to 
add a work around in u-boot or Linux. Is there a preference of one over 
the other? The exception handling in u-boot is premature and will 
require more work to add a work around. Is there still a possibility of 
adding the work around in Linux?

-- 
Murali Karicheri
Linux Kernel, Keystone
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