> On Dec 16, 2015, at 7:41 AM, Robert Nelson <[email protected]> wrote:
> 
> 
> 
> On Wed, Dec 16, 2015 at 9:31 AM, William Hermans <[email protected] 
> <mailto:[email protected]>> wrote:
> SPI works great on v4.1.x now, just pay attention this this little
> spi-dma-disable hack:
> 
> https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-SPIDEV0-00A0.dts#L54
>  
> <https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-SPIDEV0-00A0.dts#L54>
> 
> "ti,pio-mode;"
> 
> Otherwise, the spidev interface will lock up on the 160'th bit...
> 
> (3.8 never used dma on spi, so this isn't a regression in speed..)
> 
> Is it possible to control the SPI hardware through the PRU, and if so, would 
> that hack still matter Robert ? No idea if spidev is used in such a case or 
> not . . . 
Yes, you can control the SPI with the PRU. Take the SPI driver from Starterware 
and adapt it to work on the PRU and then build with the PRU C compiler. SPIDEV 
is a Linux feature and has nothing to do with the PRU. Starterware is barebone 
programming where you manipulate the peripheral, bus and clock registers 
directly using the CortexA8 ARM processor. The PRU can manipulate these same 
registers. From what I remember, there is a github project that has already 
ported some of the Starterware drivers to work on the PRU.

Regards,
John
> 
> I didn't investage that side..  It's just when used as an overlay, that's 
> needed..
> 
> If you setup a *.dtb with spi enabled in the dtb-rebuilder you don't need 
> that workaround..
> 
> https://github.com/RobertCNelson/dtb-rebuilder/blob/4.1-ti/src/arm/am335x-boneblack-spi0.dts#L140
>  
> <https://github.com/RobertCNelson/dtb-rebuilder/blob/4.1-ti/src/arm/am335x-boneblack-spi0.dts#L140>
> 
> Regards,
> 
> -- 
> Robert Nelson
> https://rcn-ee.com/ <https://rcn-ee.com/>
> 
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