[PATCH v3 1/3] ARM: BCM5301X: initial support for the BCM5301X/BCM470X SoCs with ARM CPU

[Hauke Mehrtens]

On 07/26/2013 10:55 AM, Will Deacon wrote:
> On Thu, Jul 25, 2013 at 11:42:13PM +0100, Hauke Mehrtens wrote:
>> This patch adds support for the BCM5301X/BCM470X SoCs with an ARM CPUs.
>> Currently just booting to a shell is working and nothing else, no
>> Ethernet, wifi, flash, ...
>>
>> This SoC is used in small office and home router with Broadcom SoCs.
>> This code should support the BCM4707, BCM4708, BCM4709, BCM53010,
>> BCM53011 and BCM53012 SoC. It uses one or two ARM Cortex A9
>> Cores, some highlights are 2 PCIe 2.0 controllers, 4 Gigabit Ethernet
>> MACs and a USB 3.0 host controller.
>>
>> This SoC uses a dual core CPU, but this is currently not implemented.
>> More information about this SoC can be found here:
>> http://www.anandtech.com/show/5925/broadcom-announces-bcm4708x-and-bcm5301x-socs-for-80211ac-routers
> 
> [...]
> 
>> +static int bcm5301x_abort_handler(unsigned long addr, unsigned int fsr,
>> +				 struct pt_regs *regs)
>> +{
>> +	/*
>> +	 * These happen for no good reason, possibly left over from CFE
>> +	 */
>> +	pr_warn("External imprecise Data abort at addr=%#lx, fsr=%#x ignored.\n",
>> +		addr, fsr);
>> +
>> +	/* Returning non-zero causes fault display and panic */
>> +	return 0;
>> +}
>> +
>> +static void __init bcm5301x_init_early(void)
>> +{
>> +	/* Install our hook */
>> +	hook_fault_code(16 + 6, bcm5301x_abort_handler, SIGBUS, 0,
>> +			"imprecise external abort");
>> +}
> 
> Surely you can't be serious?
> 
> At least, we need a pretty good explanation of what *exactly* is causing
> these spurious aborts before we start ignoring them unconditionally like
> this. You're effectively masking an extremely serious error indicator with
> this change.

This fault occurs once every boot sometime early in the boot process,
but the actual time this happens varies randomly.

Sadly I do not understand this completely, and I copied this from the
vendor BSP with the corresponding code documentation. They think CFE
(Common Firmware Environment, the bootloader used on these devices), did
something wrong, but I do not have the actual source of CFE and I do not
have the chip documentation. This occurs just once as far as I have seen
this, we could just catch the first one. Changing the boot loader is
also not an option, because I want to use this code on devices already
shipped to costumers and I do not have access to the boot loader source
code.

Do you know what this fault normally indicates?


Hauke