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. ;) Best regards, Tomasz -- 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
