[PATCH 1/2] PCI: iproc: Support DT property for ignoring aborts when probing

[Ray Jui]

On 4/10/2016 6:43 PM, Florian Fainelli wrote:
> On April 9, 2016 2:50:23 PM PDT, "Rafał Miłecki" <zajec5 at gmail.com> wrote:
>> Some devices (e.g. Northstar ones) may have bridges that forward
>> harmless errors to the ARM core. In such case we need an option to
>> add a handler ignoring them.
>>
>> Signed-off-by: Rafał Miłecki <zajec5 at gmail.com>
>> ---
>
>> +- brcm,pcie-hook-abort-handler: During PCI bus probing (device
>> enumeration)
>> +  there can be errors that are expected and harmless. Unfortunately
>> some bridges
>> +  can't be configured to ignore them and they forward them to the ARM
>> core
>> +  triggering die().
>> +  This property should be set in such case, it will make driver add
>> its own
>> +  handler ignoring such errors.
>
> The property is named after the function that allows you to catch abort handlers, whereas you should be describing the HW here. Something like brcm,bridge-error-forward or a better name even would be preferable.
>
>> +#ifdef CONFIG_ARM
>> +static int iproc_pcie_abort_handler(unsigned long addr, unsigned int
>> fsr,
>> +				    struct pt_regs *regs)
>> +{
>> +	if (fsr == 0x1406)
>> +		return 0;
>> +
>> +	return 1;
>
> As you later noted this prevents this driver from being a module now. Since the expectation is that either a fixed bootloader or a platform should enot produce these data aborts, or allow them to be ignored, why not just put this code back where it belongs in the machine specific file which kills many birds with the same stone:
>

I assume the module compile issue can be simply fixed by exporting 
symbol of "hook_fault_code"?

I believe ARM64 based NS2 that uses the same iProc PCIe driver might 
also need something like this (I'm still waiting for Jon Mason to give 
me some more information on the NS2 errors that he saw, which is likely 
related to this). I assume there will be something similar to the ARM 
specific "hook_fault_code" for ARM64, but then ARM64 does not have any 
"mach" specific directory. Where can this type of hook be installed for 
ARM64 based platforms if not in the PCIe driver?

> - code is ways built-in, and hook_fault_code is installed prior to PCIe loading (function is marked with __init)
> - platforms which do not need that, just do not install it for that specific code
> - it is clear which platforms need it and which do not, yet the driver remains agnostic

It's actually unclear to me which iProc platforms need this.
- We know NS needs it
- Someone mentioned NSP does not need this? But where does the 
information come from? Do we have similar PCIe connection configuration 
on NSP as NS?
- I cannot confirm whether Cygnus needs this or not since we do not have 
similar board configurations on Cygnus (on Cygnus each host is always 
connected to a single device). I can check with the ASIC team, but that 
will be a very lengthy process and I'm not sure when I can get the 
answer we need (and yes I do work at Broadcom, :))
- Jon Mason reported similar abort issues on NS2 when an externally 
connected, multi function device is used. I'm still waiting for him to 
send me the error log and see if it's the same type of data abort.

>
> NB: there could be other platforms some day needing that which also propagate the error differently, forcing you to add more and more of these codes in the PCIe driver.
>

Yes, at this point, we are unsure whether the same or different code is 
used among different platforms.

Thanks,

Ray