On 12/06/2016 09:37 PM, David.Wu wrote: > Hi Doug, > > 在 2016/12/7 0:31, Doug Anderson 写道: >> Hi, >> >> On Tue, Dec 6, 2016 at 12:12 AM, David.Wu <david.wu@xxxxxxxxxxxxxx> >> wrote: >>> Hi Heiko, >>> >>> 在 2016/12/5 18:54, Heiko Stuebner 写道: >>>> >>>> Hi David, >>>> >>>> Am Montag, 5. Dezember 2016, 16:02:59 CET schrieb David Wu: >>>>> >>>>> During suspend there may still be some i2c access happening. >>>>> And if we don't keep i2c irq ON, there may be i2c access timeout if >>>>> i2c is in irq mode of operation. >>>> >>>> >>>> can you describe the issue you're trying to fix a bit more please? >>> >>> >>> Sometimes we could see the i2c timeout errors during suspend/resume, >>> which >>> makes the duration of suspend/resume too longer. >>> >>> [ 484.171541] CPU4: Booted secondary processor [410fd082] >>> [ 485.172777] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1 >>> [ 486.172760] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1 >>> [ 487.172759] rk3x-i2c ff3c0000.i2c: timeout, ipd: 0x10, state: 1 >>> [ 487.172840] cpu cpu4: _set_opp_voltage: failed to set voltage (800000 >>> 800000 800000 mV): -110 >>> [ 487.172874] cpu cpu4: failed to set volt 800000 >>> >>>> >>>> I.e. I'd think the i2c-core does suspend i2c-client devices first, >>>> so that >>>> these should be able to finish up their ongoing transfers and not start >>>> any >>>> new ones instead? >>>> >>>> Your irq can still happen slightly after the system started going to >>>> actually >>>> sleep, so to me it looks like you just widened the window where irqs >>>> can >>>> be >>>> handled. Especially as your irq could also just simply stem from the >>>> start >>>> state, so you cannot even be sure if your transaction actually is >>>> finished. >>> >>> >>> Okay, you are right. I want to give it a double insurance at first, >>> but it >>> may hide the unhappend issue. >>> >>>> >>>> So to me it looks like the i2c-connected device driver should be fixed >>>> instead? >>> >>> >>> I tell them to fix it in rk808 driver. >> >> To me it seems like perhaps cpufreq should not be changing frequencies >> until it is resumed properly. Presumably if all the ordering is done >> right then cpufreq should be resumed _after_ the i2c regulator so you >> should be OK. ...or am I somehow confused about that? > > yes，the cpufreq and regulator should start i2c job after they resume > properly. > >> >> Also note that previous i2c busses I worked with simply returned -EIO >> in the case where they were called when suspended. See >> "i2c-exynos5.c" and "i2c-s3c2410.c". > > In "i2c-exynos5.c", it seems that using the "i2c->suspended" to protect > i2c transfer works most of the time. Of course it could prevent the next > new i2c transfer to start. But in one case, if the current i2c job was > not finished until the i2c irq was disabled by system suspend, the i2c > timeout error would also happen, as the current i2c job may have a large > data to transfer and it lasts from a long time. And this means you have bug in some of I2C client drivers which do not stop their activities during suspend properly (most usual case - driver uses work and this work still active during suspend and can run on one CPU while suspend runs on another). At the moment .suspend_noirq() callback is called there should be no active I2C transactions in general. > > So is it necessary to add a mutex lock to wait the current job to be > finished before the "i2c->suspended" is changed in i2c_suspend_noirq()? > You need to catch and fix all driver who will try to access I2C after your I2C bus driver passes suspend_noirq stage. Smth, like [1], uses i2c_lock_adapter(). [1] https://git.ti.com/android-sdk/kernel-omap/commit/125ef8f7016e7b205886f93862288a45a312b1d8 -- regards, -grygorii -- 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
