Hello all, Any suggestion about the below questions?
Thanks, Thomas On Thu, 7 Aug 2014 09:57:33 +0200, Thomas Petazzoni wrote: > Hello, > > I am currently writing a driver for the XHFC ISDN chip from Cologne > Chip, which is interfaced over SPI with an ARM processor (i.e it's not > the typical PCI card setup). The fact that it's over SPI means that > talking to the XHFC chip is quite slower than talking to memory-mapped > devices such as PCI devices. > > With the default DAHDI_CHUNKSIZE of 8 bytes, we need to have an > interrupt every millisecond to push and pull data from/out of the XHFC > chip. And it's quite difficult to do all the necessary SPI > communication in one millisecond (not really transferring the 8 bytes, > but doing all the administrative stuff such as reading the interrupt > flags, etc.). Getting interrupts every millisecond is also generating a > fairly significant CPU load. > > Ideally, we would like to be able to get less interrupts, like only > every 4 ms, and therefore push and pull 32 bytes of data at each > interrupt. > > This would however require raising the DAHDI_CHUNKSIZE to 32 bytes > instead of the default 8 bytes. What are the consequences of such an > increase of the chunk size ? > > Back in 2010, there was a thread at > http://lists.digium.com/pipermail/asterisk-ss7/2010-March/003544.html > showing that apparently wasn't really simple. And the document at > http://www.sangoma.com/assets/docs/misc/2009_10_09_How_to_Reduce_Asterisk_System_Loads.pdf > indicates that if you use any other value than 8 bytes for > DAHDI_CHUNKSIZE, you cannot use any software echo cancellation. But > both of these things are 4-5 years old, so I'm not sure to what extent > they apply to the current DAHDI code base. > > Do you have any insights/experience about the possibility of raising > the DAHDI_CHUNKSIZE ? > > Thanks a lot, > > Thomas -- Thomas Petazzoni, CTO, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- _____________________________________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-dev mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-dev
