Re: [PATCH] MIPS: Fix errata for some 1074K cores.

[Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>]

It is not mine, I just fixed an existent code which applies a wrong 
errata to 1074K.
Errata fix did exist before me.

- Leonid.


On 09/12/2013 08:12 AM, Paul Burton wrote:
> Agreed, my point is not about your code but your commit message. If 
> I'm reading a commit which works around CPU errata I should not have 
> to go and ask the hardware engineers or even read an errata document 
> in order to know what you're doing. Your commit message should explain 
> the errata, its effects and how your patch works around the problem.
>
> Paul
>
> On 12/09/13 16:05, Florian Fainelli wrote:
>> 2013/9/12 Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>:
>>> Treat it as is.
>>>
>>> It is a dirty laundry of HW engineers and you may need to 
>>> communicate with them or read Errata docs on CPU.
>>>
>>> If it is about a way how it is written - ask Steven, initially it 
>>> was in mainland probe code but he think it should be a separate 
>>> function. I just corrected him, pointing that erratas on 74K and 
>>> 1074K are different. But because he insist on having the same 
>>> CPU_74K for both, so...
>> If you take a look at another CPU company such as ARM, they provide
>> lengthy explanations for their various Erratas:
>>
>> config PJ4B_ERRATA_4742
>>          bool "PJ4B Errata 4742: IDLE Wake Up Commands can Cause the
>> CPU Core to Cease Operation"
>>          depends on CPU_PJ4B && MACH_ARMADA_370
>>          default y
>>          help
>>            When coming out of either a Wait for Interrupt (WFI) or a 
>> Wait for
>>            Event (WFE) IDLE states, a specific timing sensitivity 
>> exists between
>>            the retiring WFI/WFE instructions and the newly issued 
>> subsequent
>>            instructions.  This sensitivity can result in a CPU hang 
>> scenario.
>>            Workaround:
>>            The software must insert either a Data Synchronization 
>> Barrier (DSB)
>>            or Data Memory Barrier (DMB) command immediately after the 
>> WFI/WFE
>>            instruction
>>
>> I really think that you should aim for the same level of information
>> so that people know whether this is relevant for their platform,
>> whether they have the ECO applied etc...
>