Re: [PATCH v3] parisc: Fix crash due alternative coding for NP iopdir_fdc bit

[Helge Deller <deller@gmx.de>]

On 28.05.19 20:40, John David Anglin wrote:
> On 2019-05-28 1:39 p.m., Sven Schnelle wrote:
>> Hi,
>>
>> On Tue, May 28, 2019 at 07:24:29PM +0200, Rolf Eike Beer wrote:
>>> Am Dienstag, 28. Mai 2019, 19:06:48 CEST schrieb John David Anglin:
>>>> On 2019-05-28 11:38 a.m., Sven Schnelle wrote:
>>>>> Interesting. Now that you mention it i see that my C3750 reports the same.
>>>>> Google returned the following page
>>>>> https://support.hpe.com/hpsc/swd/public/detail?swItemId=PF_CCJ70020
>>>>>
>>>>> Which is 2.0, and only mentions "C3650/C3700/C3750/J6700/J6750 firmware"
>>>>> So maybe these machines have NP set, and machines "below" (like C3600)
>>>>> don't have it set.
>>>>>
>>>>> I wonder what happens if you try to flash a 5.0 firmware to such a box.
>>>>
>>>> From what I see, the "C3650/C3700/C3750/J6700/J6750" and "HP 9000 Model
>>>> B1000/C3000/J5000/J7000" use different firmware.
>>>
>>> Which makes sense as the former have use a 8600 CPU, while the latter have
>>> 8700 ones.
>>
>> Exactly. And as:
>>
>> a) All C3600 PDC versions clear the NP bit
>> b) All C37XX/J5000 PDC version set the NP bit
>>
>> i don't think there's some bug in the PDC. I would guess that the patch Carlo
>> reported to fix issues is just hiding the real problem. Would be interesting
>> to run Carlo's Test on a C37XX.
>
> Probably, hardware cache coherent I/O is not implemented correctly for Elroy based systems.
> https://www.hpl.hp.com/hpjournal/96feb/feb96a6.pdf
> Does it work on C360?

I slowly start to get confused...
Just thinking about another possibility: Maybe we can rely on the value of the
NP iopdir_fdc bit only on machines with >= PA8700 CPUs?
For older machines (which would need opdir_fdc) HP-UX or other operating
systems decides on the found CPU.
This would explain why it's not  set on Carlo's C3600, and if Sven's C240
(with a PA8200 CPU) doesn't has the bit set too, then this could explain this theory.

Helge