[alsa-devel] r8a7790 only has audio when clock is forced on

[Kuninori Morimoto]

Hi Violeta, Mark

> Adding Morimoto-san who does most of the work on those drivers upstream
> - it's always best to CC relevant maintainers/developers on kernel stuff
> as things only on the lists are easily missed.  Not deleting context so
> he sees it.

Thank you for adding me.
I want to help you

> > We have a problem where audio on r8a7790 is not working due to it not
> > sending interrupts.

I need to ask you something

- Are you using lager board ?
- Which kernel are you using ?
- Does your kernel booted from legacy code (= using board-lager.c)
  or from DT code (= using board-lager-referenct.c) ?

> We've made a hack to force /mstp10_clks /on that makes the audio work.
> Further investigation showed that it's only needed to force SSI(ALL) on,
> but, as far as we know, the manual doesn't say anything about it having to
> be kept on.

YES. all SSI port needs SSI(ALL).
(Actually, all SRC needs SRC(ALL) too if you use it)

Basically, R-Car sound is very complex IP.
The interrupt/data register/DMA selection are depends on your "data path"

This driver is producing many steps to use it.

At 1st, you can use "PIO transfer". this is not good performance,
but, very easy settings. you can check your basic setting by this.
(power/codec/pin/clock...)

The data path is..

          PIO
    [MEM] ---> [SSI]

Next step is "using DMA". but, R-Car sound has 2 DMAs (Audio DMAC/Audio DMAC peri peri)
And, these DMAC usage is complex too. So, you can use basic DMA transfer as DMA 1st step.
The data path is..

       Audio DMAC
    [MEM] ---> [SSI]

Next step is more complex. use SRC

                     Audio DMAC
        Audio DMAC    peri peri
    [MEM] ---> [SRC] --->[SSI]

Final step is using DVC

                            Audio DMAC
        Audio DMAC           peri peri
    [MEM] ---> [SRC] ---> [DVC] --->[SSI]


Actually, lagacy boot is supporting above all path.
But, DT boot is supporting 1st/2nd step only at this point
(On rsnd driver side, DMAEngine DT is not yet supporing)
I want to support 3rd/4th step on DT, but I'm busy now...

I pushed my local patches which are based on LTSI v3.4 + our original patches.
These are tring to use sound as legacy code (= not DT) for lager/koelsh.
Maybe not good fit too you, but can help ?

https://dl.dropboxusercontent.com/u/2774973/lager-koelsh-sound.tar.bz2