On 14/01/16 08:29, Julio Cruz wrote: > Hi again, > > After digging on this issue, the SPI data loss was due to: > > 1. The latency of some kernel drivers/modules. After disable some > modules as suggested by Mat and tglx [1] the SPI handler latency was > better, however still have some missing. > 2. The SPI thread priority was too low. After setting the > policy/priority as suggested by Daniel [2], the SPI response was as > expected. > > The interrupt latency depends on different factors, and those are very > interesting once you research it (interrupt controller implementation, > device priority of the interrupt, others drivers, etc...). Sorry for > the noise about this issue. > > Maybe this experience could be of interest for others SPI based drivers. > > Julio > Thanks for the updates. Certainly of interest in general and good to have a set of references to look at when next this question is raised! Jonathan > ---- > [1] Long max latencies on Wandbaord / Freescale i.MX6 > http://marc.info/?l=linux-rt-users&m=144368690819933&w=2 > ---- > [2] cyclictest versus custom SPI based system > http://marc.info/?l=linux-rt-users&m=145271122200825&w=2 > > On Tue, Jan 12, 2016 at 11:50 PM, Julio Cruz <jcsistemas2001@xxxxxxxxx> wrote: >> Hi, >> >> I'm running an acquisition system @1KHz sampling frequency (27 >> bytes/sample) with libiio as interface between the application and the >> IIO driver (SPI based). The network and local context are working as >> expected. >> >> However, the system have some data loss at SPI level (confirmed by >> scope) even if the data is not pushed to the buffer >> (iio_push_to_buffers). The scope show that every 1.4 sec (aprox), the >> handler is not called. It seem other process is taking priority over >> this. >> >> I'm trying to find the process that is taking over the SPI/IRQ handlers. >> >> - My system is running in ext4 (on SD) and maybe this could be the >> problem (journal)? >> - Implement a RT and review interrupt context as suggested by Xander >> (http://marc.info/?l=linux-iio&m=143933412720586&w=2)? >> - I would like to implement a DMA buffer as suggested by Lars (two >> month ago) but I'm not sure this will help in this case >> (http://marc.info/?l=linux-iio&m=144475305426138&w=2), for now. >> >> In any case, any advice to address this problem is welcome. >> >> Thanks > -- > 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 > -- 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
