On Tue, Jun 21, 2011 at 10:03 PM, Stefan Schmidt <[email protected]> wrote: > > Hello. > > On Thu, 2011-06-16 at 17:44, Eric Miao wrote: > > On Thu, Jun 16, 2011 at 5:19 PM, Stefan Schmidt > > <[email protected]> wrote: > > > > > > Its either 8bit or 16bit for a message. The mentioned problem happens > > > on a 8 bit message. It does nothing else then writing to a defined > > > register address to trigger the hardware sending the data in the FIFO. > > > > This might get too much overhead. I didn't check the source code, but > > my guess is it's waiting for interrupt for each message, and once the > > interrupt of message being flushed out happens, it starts the next one > > waiting for the FIFO empty interrupt coming. Did you try stuff more > > bytes into a single message? > > Took me some time to implement and test al kind of different > scenarios. As you suggested I tried to stuff more bytes into a message > as well as testing all kind of combination with tx and rx thresholds, > timout, PIO and DMA, cs_change , etc. No change. > > I then bit the bullet and changed the board to use the spi_gpio driver > instead of pxa2xx. After some struggling (make sure you setup pin > config correctly :)) I got it working but with the same result. > > My last test block was around using spi_async() instead of spi_sync > and as well I was not able to reach my timing criteria. :( > > To me it seems right now as if it is just not possible to reach > something in the 100 usec range with the SPI framework. Obviuously I > would be loved to be proven wrong. :) > > As I'm running way out of time for this part of my project I'm back to > the driver now trying to find a solution that avoids the tight timing > criteria.
I think for a time budget like this, you may want to try a dedicated polling driver avoid all the interrupt/wait stuff, that's going to maximize the throughput. If that's even not possible, it might be HW limitations. > > Eric, thanks again for your fast and helpfull mails. No problem, most welcome. > > regards > Stefan Schmidt ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
