sDMA on i.mx7d

[Alexandre Belloni]

Hi,

I've been trying to get a PCM3168s codec with a Colibri iMX7 using TDM
on SAI2.
I've got it working properly with the 4.1.35 kernel from Toradex (based
on the 4.1.15 from Freescale).
It is working fine with and without providing a firmware to the sDMA.

But, I couldn't get that to work with v4.9. I actually managed to
reproduce the issue using the SGTL5000 so I don't have any patch on top
of v4.9.

I really suspect the DMA driver as the issue varies with the selected
period/buffer size.

Basically, the samples in a period are in the correct order but the
periods are mixed up.

This is what I'm playing in a loop:
http://free-electrons.com/~alexandre/source.png

This is the output I get:
http://free-electrons.com/~alexandre/playback.png

The configuration for the cyclic transfer seems to be fine and I don't
know enough about the sdma to investigate further.
I can try to backport b7d2648ac3d4 "dmaengine: imx-sdma: Add i.MX7
support" to v4.8 and test I you think that can be useful

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com