On 03.11.2017 08:17, Jonathan Cameron wrote:
I assume we are talking a hw fifo? I'm going to guess with a watershed interrupt...
What exactly does "watershed interrupt" mean in this context ? Per ADC we have 2 buffers, while one is filled by adc, while the other is read out by the the cpu. (unfortunately they're not visible as a memory block, but only a fifo head register - hopefully we can change that, so i can just use memcpy() or dma engine). When one buffer is full, the corresponding interrupt is trigged and adc switches to filling the other one.
Triggers are used when you have a single interrupt for each sample pass of a given ADC. (a so called scan - of data captured at the same time - or often based on an internal shared sequencer).
Is a sample pass limited to one sample, or can it be a whole block of samples ?
So typically when you have a flow involving a hardware buffer you skip the trigger and have the interrupt controller push data directly to the buffers from the interrupt handler thread.
That was my idea. Is there already some driver which does exactly that ? (with blocks of samples instead of just a single one)
If you have 3 different interrupts and the ADCs have separate buffers then you can't guarantee to do reads from all on a single interrupt?
Theoretically, the adcs should be synchronous, but the buffers and interrupts are separated (the original requirements demanded separate sampling rates defined potentially separate sampling rates, but in the meantime changed to same rate for all).
In that case, as far as IIO is concerned you have 3 separate ADC systems which will need to each be a separate IIO device.
Why not 3 channels w/ separate interrupts ? Do multiple channels of one device always share the same sampling rate and sampling points (like stereo channels on an audio device) ?
There is also infrastructure to match the fifo watershed with the software one so that you only read from the hardware when you want to read it from userspace.
How does that work ? --mtx -- Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@xxxxxxxxx -- +49-151-27565287 -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
