Re: [PATCH] arm64: dts: rockchip: add HDMI sound node for rk3328-rock64

[Katsuhiro Suzuki]

Hello Heiko,

On 2019/02/12 20:12, Heiko StÃbner wrote:
> Hi,
>
> Am Montag, 4. Februar 2019, 13:59:37 CET schrieb Katsuhiro Suzuki:
> > On 2019/02/03 18:06, Heiko Stuebner wrote:
> > > Am Samstag, 2. Februar 2019, 05:34:44 CET schrieb Katsuhiro Suzuki:
> > > > This patch adds HDMI sound (I2S0) node and remove dma properties
> > > > from UART2 node for rock64.
> > > >
> > > > The DMAC of rk3328 can use 8 channels at same time. Currently, total
> > > >
> > > > 7 channels are used as follows:
> > > >     - I2S1  2ch
> > > >     - UART2 2ch
> > > >     - SPDIF 1ch
> > > >     - SPI0  2ch
> > > >
> > > > HDMI audio using I2S0 that requires 2ch but DMAC has only 1 channel.
> > > >
> > > > UART2 can work without DMA resources, so this patch removes dma
> > > > allocation for UART2 and reuses it to I2S0.
> > >
> > > I don't follow that description. How can i2s0 re-use the uart2 dma
> > > channels? Looking at the dma table in the TRM, uart2 has channels 6+7
> > > while i2s0 uses channels 11+12. They should just run concurrently?
> >
> > Sorry for confusing... 6 or 7 is as ID number of slave DMA channel.
> > TRM calls it 'Req number'. Req number 6+7 and 11+12 can work
> > concurrently but TRM says DMAC can transfer 8 DMA channels at same
> > time. So all 16 Req numbers cannot activate at same time. It should
> > be keep less or equal than 8 numbers.
>
> But that "shortcoming" of having more requests than channels is not
> something specific to the pl330, instead most dma controllers have that
> "problem", which seems to get solved by the virt-dma mechanism of
> dmaengine - which pl330 doesn't use so far. (but see pl080 for example)

I understand. I drop these patches.


> The devicetree only describes the hardware and is never meant as a
> configuration space for kernel-code shortcomings.

Yes, right. I don't want to use device-tree as configuration space,
so which is better?

- Fix the pl330 driver first and after that add HDMI-sound node
  to device-tree.
- Just add HDMI-sound node to device-tree. If someone (include me)
  want to support virt-dma on pl330 driver, they will fix it.
  (PL330 will face error but all sounds works fine and UART still
  works fine with DMA error)

> Heiko

Best Regards,
Katsuhiro Suzuki