On Mon, 20 Sep 2021 10:37:39 +0200 Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > Hi Jonathan, > > jic23@xxxxxxxxxx wrote on Sat, 18 Sep 2021 18:13:08 +0100: > > > On Wed, 15 Sep 2021 12:18:32 +0200 > > Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > > Hi Jonathan, Nuno, > > > > > > jic23@xxxxxxxxxx wrote on Sun, 5 Sep 2021 17:10:46 +0100: > > > > > > > On Thu, 2 Sep 2021 23:14:36 +0200 > > > > Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote: > > > > > > > > > So far the driver only supported to use the hardware cnvst trigger. This > > > > > was purely a software limitation. > > > > > > > > > > The IRQ handler is already registered as being a poll function and thus > > > > > can be called upon external triggering. In this case, a new conversion > > > > > must be started, and one must wait for the data to be ready before > > > > > reading the samples. > > > > > > > > > > As the same handler can be called from different places, we check the > > > > > value of the current IRQ with the value of the registered device > > > > > IRQ. Indeed, the first step is to get called with a different IRQ number > > > > > than ours, this is the "pullfunc" version which requests a new > > > > > > > > pullfunc? > > > > > > > > > conversion. During the execution of the handler, we will wait for the > > > > > EOC interrupt to happen. This interrupt is handled by the same > > > > > helper. This time the IRQ number is the one we registered, we can in > > > > > this case call complete() to unlock the primary handler and return. The > > > > > primary handler continues executing by retrieving the data normally and > > > > > finally returns. > > > > > > > > Interesting to use the irq number.. > > > > > > > > I'm a little nervous about how this has ended up structured. > > > > I'm not 100% sure my understanding of how you've done it is correct. > > > > > > > > We should have the following situation: > > > > > > > > IRQ IN > > > > | > > > > v > > > > Trigger IRQ / EOC IRQ (this is the spi->irq) (currently iio_trigger_generic_data_poll_ready) > > > > | | > > > > --------- v > > > > | | complete > > > > v v > > > > TrigH1 (TrigH2) (these are the IRQs below the irq_chip IIO uses to demux triggers) > > > > > > > > > > > > So when using it's own trigger we are using an internal interrupt > > > > tree burried inside the IIO core. When using it only as an EOC interrupt we shouldn't > > > > be anywhere near that internal interrupt chip. > > > > > > > > So I'm surprised the IRQ matches with the spi->irq as > > > > those trigH1 and trigH2 will have their own IRQ numbers. > > > > > > > > For reference I think your architecture is currently > > > > > > > > IRQ IN > > > > | > > > > v > > > > Trigger IRQ > > > > | > > > > v > > > > TRIG H1 > > > > Either fills the buffer or does the completion. > > > > > > > > I am a little confused how this works with an external trigger because the Trig H1 interrupt > > > > should be disabled unless we are using the trigger. That control isn't exposed to the > > > > driver at all. > > > > > > > > Is my understanding right or have I gotten confused somewhere? > > > > > > I think the confusion comes from the fact that in the > > > current implementation, Trigger IRQ and EOC IRQ handlers are the same. > > > This comes from a possible misunderstanding in the previous review, > > > where I understood that you and Nuno wanted to keep using > > > iio_trigger_generic_data_rdy_poll() hand have a single handler in the > > > driver (which I think is far from optimal). I can try to split that > > > handler again to have two distinct paths. > > That is the right thing to do. The split should be done a little differently > > than you have it in v3. I've added comments to that patch. > > > > Data ready triggers are always a little messy because we end up with a split that > > is: > > > > Trigger side - Interrupt comes in here... > > > > --------- GENERIC IIO HANDLING ----- Take the trigger and routes it to the device code --- > > > > Device side - We do the data reading here. > > > > The reason for this is that we may well have other devices using the same trigger > > and we want to keep the model looking the same for all devices. > > > > A push into an iio buffer should always be on the device side of that boundary. > > This is much clearer, I think I have got the main idea. > > However I have a question that is specific to the current situation. In > the case of this particular device, I don't really understand how > another device could use the same trigger than the hardware one, > because we have no indication of the trigger being latched. When we get > the information the data is already in the FIFO, this means we get the > information much later than when the hardware transitioned to indicate > a conversion request. Is it that in your model, we should be able to > use the EOC IRQ handler to trigger another IIO device, even though > this implies an additional delay? It's not ideal, but sometimes it is better to have somewhat consistent 'synchronization' between multiple devices. You are correct that anything else using a data ready trigger will be a bit late - but the frequencies will at least be matched. Not great but the best possible under these circumstances. If it's possible to use a truely shared hardware trigger that is obviously better than you can do here. Jonathan > > Thanks, > Miquèl > > > > > I also can't see a path in which the eoc interrupt will get fired for raw_reads. > > > > > > > > Could you talk me through how that works currently? > > > > > > > > I suspect part of the confusion here is that this driver happens to be using the > > > > standard core handler iio_trigger_generic_data_rdy_poll which hides away that > > > > there are two interrupt handlers in a normal IIO driver for a device with a > > > > trigger and buffered mode. > > > > 1 for the trigger and 1 for the buffer. Whether the buffer one is a result > > > > of the trigger one (via iio_poll_trigger) is down to whether the device is > > > > using it's own trigger or not. > > > > > > Also, to answer Nuno about the question: is this actually working: IIRC > > > I mentioned it in the cover letter but my hardware does not have the > > > EOC line wired so I am unable to actually test that I am not breaking > > > this. My main goal is to be able to use external triggers (such as a > > > timer) and I am a bit struggling with the constraints of my hardware + > > > the design of this chip. > > > > > > I will provide a third implementation in v3 and if this still does not > > > fit your mental model please guide me with maybe an untested code > > > snippet just to show me how you think this should be implemented. > > > > > > Thank you both for the numerous reviews and precious feedback anyway! > > > Miquèl > > >
