Messages in this thread | | | From | Kevin Hilman <> | Subject | Re: [PATCH] i2c: exynos5: Properly use the "noirq" variants of suspend/resume | Date | Mon, 23 Jun 2014 15:19:11 -0700 |
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Doug Anderson <dianders@chromium.org> writes:
[...]
> On Fri, Jun 20, 2014 at 4:59 PM, Tomasz Figa <tomasz.figa@gmail.com> 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.
Kevin
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