Re: [PATCH v2, 1/1] mtd: devices: m25p80: Add PM suspend resume support

[Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>]

On 01/20/2017 12:42 PM, Marek Vasut wrote:
> On 01/20/2017 09:23 PM, Florian Fainelli wrote:
>> On 01/20/2017 12:13 PM, Marek Vasut wrote:
>>> On 01/20/2017 09:07 PM, Florian Fainelli wrote:
>>>> On 01/20/2017 12:02 PM, Marek Vasut wrote:
>>>>> On 01/20/2017 07:50 PM, Kamal Dasu wrote:
>>>>>> On Fri, Jan 20, 2017 at 12:22 PM, Marek Vasut <marex@xxxxxxx> wrote:
>>>>>>> On 01/20/2017 05:33 PM, Kamal Dasu wrote:
>>>>>>>> Marek,
>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> OK, so I'm fine with leaving the patch as is for now but I would like Marek
>>>>>>>>>> review just to be sure we didn't miss something: Marek, any comments?
>>>>>>>>>>
>>>>>>>>>> I just have one more comment below but it's only a detail.
>>>>>>>>>
>>>>>>>>> What would happen if you have a FS attached on this SPI NOR (like UBIFS)
>>>>>>>>> and you suspend with this patch ? Will it survive ?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> I have tried with both jffs2 rw and ubifs rw rootfs on spi-nor
>>>>>>>> booting from spi-nor partitions while  active filesystem operations
>>>>>>>> were going on over suspend/resume cycles. And it survives.
>>>>>>>
>>>>>>> Can you elaborate on your test a bit ?
>>>>>>>
>>>>>>
>>>>>> The power management test  puts  board in standby mode,  during
>>>>>> standby the DRAM is in refresh and power to the spi-nor is removed.
>>>>>> After a set timeout the board wakes up again and resumes from where it
>>>>>> left off. This pm test is run while a cp command is invoked where a
>>>>>> file is transferred to the rw rootfs. The test loops through said
>>>>>> number of iterations of suspend and resumes cycles. The copy
>>>>>> operations is eventually done over a few cycles. Once the test is
>>>>>> completed  filesystem should have no corruptions, the copied files
>>>>>> should compare and rootfs should be intact.  This test was repeated
>>>>>> with jffs2 as well as ubifs rootfs flashed on spi-nor device.
>>>>>
>>>>> Would be much nicer if you could just share the script you used.
>>>>
>>>> Not sure if this is even possible, but maybe we could. What part of
>>>> Kamal's description of the test is not clear here?
>>>
>>> I cannot check the test and see what was really done, the code is the
>>> best description. If someone tells me a script (which is likely about
>>> 20 lines) cannot be shared, that's fishy.
>>
>> The reason why I mentioned that is that it's not like our test suite is
>> somewhere out there on Github and we could just point you to it, it
>> could take some time and effort to extract the script, period. It's not
>> fishy, it's just not ideal, and it is a consequence of working in a
>> corporate environment.
> 
> Somehow, it feels like you're digging yourself in deeper and deeper ...
> now I'm seriously curious how this was tested. Esp. since this patch
> has potentially massive impact and could annoy a lot of people if it
> breaks things, so a lot of testing will have to happen on this one.

And somehow it feels like you don't even try to understand that the test
may be part of an existing test framework thus making it harder to
extract and send as a standalone shell script. Not everything we do is
open source, and although there is not necessarily a reason why not, it
just is. Not saying this is impossible, or that our testsuite is the
best thing since we discovered hot water, just don't expect it to show
up instantly, period.

Keep in mind that asking for an explanation about how this was tested
initially is a perfectly reasonable thing to do, and you may, or may not
be satisfied with the answer, clearly you are not, but asking for test
case is just not common thing, it also indicates that you absolutely
don't trust Kamal's explanation and understanding of the problem, and
that can be misinterpreted at best.

> Having a testcase would help ...

Agreed, just like having a proper test suite geared towards MTD/SPI that
we could contribute to (not necessarily LTP) would help as well. So,
where do we start now?
-- 
Florian
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