Re: [PATCH] i2c: exynos5: Properly use the "noirq" variants of suspend/resume

[Tomasz Figa]

On 24.06.2014 00:19, Kevin Hilman wrote:
> Doug Anderson <dianders@xxxxxxxxxxxx> writes:
> 
> [...]
> 
>> On Fri, Jun 20, 2014 at 4:59 PM, Tomasz Figa <tomasz.figa@xxxxxxxxx> wrote:
>>>
>>> I'm not sure noirq is going to work correctly, at least not with current
>>> callbacks. I can see a call to clk_prepare_enable() there which needs to
>>> acquire a mutex.
>>
>> Nice catch, thanks!  :)
>>
>> OK, looking at that now.  Interestingly this doesn't seem to cause us
>> problems in our ChromeOS 3.8 tree.  I just tried enabling:
>>   CONFIG_DEBUG_ATOMIC_SLEEP=y
>>
>> ...and confirmed that I got it on right:
>>
>> # zgrep -i atomic /proc/config.gz
>> CONFIG_DEBUG_ATOMIC_SLEEP=y
>>
>> I can suspend/resume with no problems.  My bet is that it works fine because:
>>
>> * resume_noirq is not considered "atomic" in the sense enforced by
>> CONFIG_DEBUG_ATOMIC_SLEEP (at least not in 3.8--I haven't tried on
>> ToT)
> 
> The reason is because "noirq" in the suspend/resume path actually means
> no *device* IRQs for that specific device.
> 
> It's often assumed that the "noirq" callbacks are called with *all*
> interrupts disabled, but that's not the case.  Only the IRQs for that
> specific device are disabled when its noirq callbacks run.

Thanks for clarifying this. This means that we should be fine with the
noirq variant then.

Best regards,
Tomasz
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