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

[Florian Fainelli]

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 at denx.de> 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?

Even without doing actual copy across suspend/resume cycles, a device
which has a power domain architecture where the SPI-NOR flash gets
powered down during a suspend state, and the root filesystem is on that
flash would expose issues without Kamal's patch here.
-- 
Florian