On 6/2/24 18:08, Jonathan Cameron wrote: > On Thu, 30 May 2024 16:07:22 +0200 > Denis Benato <benato.denis96@xxxxxxxxx> wrote: > >> On 1/15/24 10:37, Jonathan Cameron wrote: >>> On Sun, 14 Jan 2024 21:04:12 +0100 >>> Denis Benato <benato.denis96@xxxxxxxxx> wrote: >>> >>>> On 1/13/24 18:46, Jonathan Cameron wrote: >>>>> On Wed, 10 Jan 2024 23:35:01 +0100 >>>>> Denis Benato <benato.denis96@xxxxxxxxx> wrote: >>>>> >>>>>> Hello, >>>>>> >>>>>> With this mail I am submitting bug report that is probably related to >>>>>> iio-trig-hrtimer but there is also the possibility for it to be >>>>>> specific to bmi160 and bmi323. >>>>>> >>>>>> The described problem have been reproduced on my handheld PC (Asus >>>>>> RC71L) and in another handheld PC with two different gyroscope >>>>>> drivers: bmi323 (backported by me on v6.7, on RC71L) and bmi160. >>>>>> >>>>>> My target hardware (RC71L that yeld to this discovery) has a bmi323 >>>>>> chip that does not have any interrupt pins reaching the CPU, yet I >>>>>> need to fetch periodically data from said device, therefore I used >>>>>> iio-trig-hrtimer: created a trigger, set the device and trigger >>>>>> sampling frequencies, bound the trigger to the device and enabled >>>>>> buffer: data is being read and available over /dev/iio:device0. >>>>>> >>>>>> While in this state if I suspend my handheld I receive (from dmesg) >>>>>> the warning reported below and at resume data is not coming out of >>>>>> the iio device and the hrtimer appears to not be working. If I create >>>>>> a new trigger and bind the new trigger to said iio device and >>>>>> re-enable buffer data does come out of /dev/iio:device0 once more, >>>>>> until the next sleep. >>>>>> >>>>>> Since this is important to me I have taken the time to look at both >>>>>> drivers and iio-trig-hrtimer and I have identified three possible >>>>>> reasons: >>>>>> >>>>>> 1) iio-trig-hrtimer won't work after suspend regardless of how it is >>>>>> used (this is what I believe is the cause) >>>>> me too. >>>> who and how should investigate this issue? Would putting a kprintf in the hrtimer callback be enough to check? >>> The warning you have pretty much points at this being the problem, but sure >>> you could add a print there to be absolutely sure. >>> >>>> >>>> >>>> Just to make sure I understood correctly: is this a separate issue from the warning I receive or are those linked? >>> >>> I think it's all one issue. >> Hello, >> >> Sorry for the delay, I was able to find some time just recently. >> >> Sadly I don't think anymore this is just one issue: >> >> I have setup a proof of concept that at suspend sets a boolean to true and at resume sets the same boolean to false, and on trigger_handler returns IRQ_NONE if the device is sleeping (everything guarded by an additional mutex) and it solved the warning: no more regmap access are being performed after the device is put to sleep, but unfortunately the acquisition does not automatically resume after waking up the device. >> >> How shall we proceed? > > It's been a while (and a busy day of reviewing) so I'm struggling > a bit with the best away forwardHello, Don't worry about it, I don't have much time available either. That stuff is as precious as gold! Thank you kindly for your time! > > A hackyish approach might be to mask the interrupt at device side > (fake interrupt used as part of the tree from a trigger to a pollfunc). > A tidy wrapped up version of this might be the best route forwards > though it won't currently stop the hrtimer merrily poking interrupts > at no oneI am sorry but I am not sure I understood this correctly: do you mean having something "in-between" iio-trig-hrtimer and the target iio device and use that to selectively poll the device? > > As a hack, could you try having your suspend call disable_irq() on > the irq found in iio_dev->poll_func->irq and reenable it in resume? > That might be sufficient. I used disable_irq and enable_irq as suggested and it works perfectly: I tested it four times and all four times (in a row) data flow resumed after s2idle-suspending the device. I can do more testing, but this is already looking very good and I'm happy (I don't have knowledge about iio internals so I am unable to tell if what I did will introduce some race conditions). As a reference I leave here the github link to the branch I have been experimenting with: https://github.com/NeroReflex/linux/commits/bmi323-pollfunc/ (Please don't mind that proof-of-concept code being copied and partially commented from bmc150-accel). No errors are printed out and combining that info with the fact it's now working it can only means pollfunc and irq are both non-NULL and non-zero at both suspend and resume. > > Check poll_func goes somewhere first though and that irq is > 0 > I think that will call iio_trig_subirq_mask() which should block > any further interrupts until it's unmasked again. > > We'll need to ensure this doesn't race with pollfunc going away though > which will make it more complex, but the above test should tell us > if there is a fairly smooth path to making this work. > > I'll try and find time to do some testing myself, but it won't be > for a few weeks :( > > Thanks, > > Jonathan Thank you again for your guidance, Denis Benato > > >>> >>>>> >>>>>> 2) iio-trig-hrtimer is stopped by the -ESHTDOWN returned by the >>>>>> function printing "Transfer while suspended", however that stack >>>>>> trace does not include function calls related to iio-trig-hrtimer and >>>>>> this seems less plausible 3) bmi160 and bmi323 appears to be similar >>>>>> and maybe are sharing a common bug with suspend (this is also why I >>>>>> have maintainers of those drivers in the recipient list) >>>>>> >>>>>> Thanks for your time, patience and understanding, >>>>> >>>>> Hi Denis, >>>>> >>>>> I suspect this is the legacy of the platform I used to test the hrtimer >>>>> and similar triggers on never had working suspend and resume (we ripped >>>>> support for that board out of the kernel a while back now...) >>>>> Hence those paths were never tested by me and others may not have cared >>>>> about this particular case. >>>>> >>>>> Anyhow, so I think what is going on is fairly simple. >>>>> >>>>> There is no way for a driver to indicate to a trigger provided by a separate >>>>> module / hardware device that it should stop triggering data capture. >>>>> The driver in question doesn't block data capture when suspended, which >>>>> would be easy enough to add but doesn't feel like the right solution. >>>>> >>>>> So my initial thought is that we should add suspend and resume callbacks to >>>>> iio_trigger_ops and call them manually from iio device drivers in their >>>>> suspend and resume callbacks. These would simply pause whatever the >>>>> trigger source was so that no attempts are made to trigger the use of >>>>> the device when it is suspended. >>>>> >>>>> It gets a little messy though as triggers can be shared between >>>>> multiple devices so we'd need to reference count suspend and resume >>>>> for the trigger to make sure we only resume once all consumers of >>>>> the trigger have said they are ready to cope with triggers again. >>>>> >>>>> As mentioned, the alternative would be to block the triggers at ingress >>>>> to the bmi323 and bmi160 drivers. There may be a helpful pm flag that could >>>>> be used but if not, then setting an is_suspended flag under the data->mutex >>>>> to avoid races. and reading it in the trigger_handler to decide whether >>>>> to talk to the device should work. >>>> I was thinking of doing this too, but I don't know if adding a mutex to frequently invoked functions is going to introduce some timing problems and so I was waiting for some comments on that matter. If nothing bad is expected I can surely try it. >>>>> >>>>> I'd kind of like the generic solution of actually letting the trigger >>>>> know, but not sure how much work it would turn out to be. Either way there >>>>> are a lot of drivers to fix this problem in as in theory most triggers can >>>>> be used with most drivers that support buffered data capture. >>>>> There may also be fun corners where a hardware trigger from one IIO >>>>> device A is being used by another B and the suspend timing is such that B >>>>> finishing with the trigger results in A taking an action (in the try_reenable >>>>> callback) that could result in bus traffic. >>>>> That one is going to be much more fiddly to handle than the simpler case >>>>> you have run into. >>>> Since more and more handheld PCs are coming and provided many vendors such as >>>> asus tends to improve what they did built on previous generations I think a >>>> general solution would be desirable. >>>> >>>> Plus there are handheld PCs that does not yet have a driver (bmi270) or are >>>> using an existing one and it would be very difficult to fix it in every of >>>> them as of now, in the future I fear it will become almost impossible or >>>> extremely time consuming as market expands. >>> >>> Both solutions require specific calls to be added to every driver that might >>> encounter this - so most drivers that support triggers other than the ones >>> they supply. >>> >>>>> >>>>> Thanks for the detailed bug report btw. To get it fixed a few >>>>> questions: >>>>> 1) Are you happy to test proposed fixes? >>>>> 2) Do you want to have a go at fixing it yourself? (I'd suggest trying >>>>> the fix in the bmi323 driver first rather than looking at the other >>>>> solution) >>>>> If we eventually implement the more general version, then a bmi323 >>>>> additional protection against this problem would not be a problem. >>>>> >>>>> Clearly I'd like the answers to be yes to both questions, but up to you! >>>>> >>>>> Jonathan >>>>> >>>>> >>>> Hello Jonathan and thank you kindly for you answer, >>>> >>>> I am very interested in the iio ecosystem as in those aforementioned >>>> handheld PCs the gyroscope plays the role as a mouse so it's a pretty >>>> important input device. >>>> >>>> I am writing to lkml not just as a single developer, but as part of a >>>> larger community in this matter: this means we will be able to test >>>> any solution and in more than just one hardware. >>>> >>>> To answers your questions: >>>> 1) yes, we all will be very happy to >>>> 2) as I am very busy right now I might be unable to do that immediately, >>>> but I will surely do it if one general solution cannot be found or is impractical. >>>> >>>> As of my limited knowledge the number of drivers now existing that are affected >>>> are 2, and the number of drivers that will be affected, once the driver is >>>> written, will be at least 3. >>> >>> The problem appears to be general unfortunately. >>> >>> I'll have to see if I can fire up something where I can actually test solutions >>> and I'm afraid I also don't have a lot of time at the moment. >>> Perhaps I can find time in the next few weeks to hack together a prototype >>> for one of the drivers you can test. >>> >>> Jonathan >>> >>>> >>>> Thank you very much for your answer, >>>> Denis >>>> >>> >> >> Thank you for you time and patience, >> Denis >
