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Subject: Re: [PATCH 01/23] devicetree: bindings: hisi_sas: add v2 HW bindings
To: Mark Rutland <mark.rutland@arm.com>
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From: John Garry <john.garry@huawei.com>
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Date: Fri, 8 Jan 2016 15:34:37 +0000
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>>>> +Optional main node properties:
>>>> + - am-max-trans : limit controller for am max transmissions
>>>
>>> Is this a boolean? Number?
>>>
>>
>> This is a boolean. It is for dealing with a quirk in the chipset: an
>> instance of the controller in the hip06 chipset requires registers
>> set with a different init value.
>
> Ok. I think the property at needs a better description for that.
>
> It's not clear to me how "limit controller for am max transmissions"
> maps to writing a specific value to some registers, but I don't know
> much about SAS.
>
> Is this some well-known thing, or values specific to hip06?
>
> Thanks,
> Mark.
>

This is a specific issue for hip06 chipset. There is a bug in the HW on 
hip06 where controller #1 has to set to 2 registers to non-default 
values to limit "am-max-transmissions". This would not be a common 
SAS/SCSI controller property and is specific to our HW.

Thanks,
John