I think that link refers to SPI slave nodes and not SPI slave mode. There are a few postings on E2E related to SPI slave mode, but none seem to have achieve anything, or at least anything that they disclosed.
My approach is to use Starterware to mock up a solution where I have McSPI and EDMA transferring data to a ping-pong buffer (DMA writes to one buffer while CPU processes the other buffer and then swap buffers at the end of each transfer). If I can achieve that then I should be able to implement the same solution in a device driver. Regards, John > On Nov 3, 2015, at 7:33 PM, William Hermans <[email protected]> wrote: > > So, I was curious about this too, and decided to do some web searching . . . > it seems there is a lot of talk about this going back since around 2009. > Although it is unclear whether or not slave mode was ever achieved, some guy > on the E2E forums claimed to have done it. Using DMA as well. > > But there is this: > http://linux-kernel.2935.n7.nabble.com/PATCH-spi-spi-omap2-mcspi-c-Add-dts-for-slave-device-configuration-td622831.html > > <http://linux-kernel.2935.n7.nabble.com/PATCH-spi-spi-omap2-mcspi-c-Add-dts-for-slave-device-configuration-td622831.html> > > And a bunch of other semi code related posts here and there that I can't make > out if they're useful or not. It's kind of a wonder that any of these guys > ever get anything done . . . > > > On Tue, Nov 3, 2015 at 4:25 PM, Matthijs van Duin <[email protected] > <mailto:[email protected]>> wrote: > On 2 November 2015 at 19:02, John Syne <[email protected] > <mailto:[email protected]>> wrote: > I have been reading your posts and I am impressed with your detailed > knowledge of the inner workings of the AM335x. Do you have any experience > with using MCSPI as a slave and using EDMA. I’m using a high speed ADC that > works as a SPI master (generates sclk). Since LInux has no support for SPI > slave mode, my plan was create a driver that sets up MCSPI in slave mode and > use EDMA to store measurements to a ping-pong buffer. > > I don't have any experience with it yet, but it sounds like it should work. > McSPI even has an option to relocate the fifo port to a 32-byte aligned > address which is specifically added to allow you to use EDMA's "FIFO mode" > (aka "constant addressing" or "streaming burst"), which enables it to slurp > 16 or 32 bytes from the McSPI fifo with a single read. > > I'm not sure about the "ping-pong buffer" though, I'm not really familiar > with linux kernel programming but I think for incoming DMA it might be better > to allocate cache-cold pages? hmm, not sure how the reduced cache activity > would balance against the increase in bookkeeping... depends also on what you > intend to do with the received data, e.g. if you're going to stuff it down a > pipe towards userspace you probably want to hand over the pages and need to > allocate new ones anyway. > > Beware BTW that if SPI mode 0 or 2 is used, chip select is required to be > deasserted between transfers. No such restriction applies to SPI mode 1 or 3, > and chip select is optional there. > > Depending on what exactly that adc is sending, there's also a (small) chance > you could interface it to McASP instead, which has a larger fifo and some > data reformatting options. > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > > > -- > For more options, visit http://beagleboard.org/discuss > <http://beagleboard.org/discuss> > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
