Tomasz Figa <tomasz.figa@xxxxxxxxx> writes: > On 24.06.2014 00:27, Doug Anderson wrote: >> Kevin, >> >> On Mon, Jun 23, 2014 at 3:19 PM, Kevin Hilman <khilman@xxxxxxxxxx> 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. >> >> Ah, so even with my fix of moving to noirq we could still be broken if >> the system decided to enable interrupts for the device before the i2c >> controller get resumed then we'd still be SOL. >> >> ...oh, but if it matches probe order then maybe we're guaranteed for >> that not to happen? We know that we will probe the i2c bus before the >> devices on it, right? > > If the mentioned device is a child of the I2C controller then the > parent-child relation determines the order. Otherwise (e.g. another, > non-I2C interrupt source that just triggers some operation on an I2C > device like voltage regulator) we're doomed. ;) Exactly. There are lots of dragons hiding here. Runtime PM is your friend. ;) Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
