Re: [PATCH 1/5] ARM: DT: tegra114: add APB DMA controller DT entry

[Laxman Dewangan]

On Saturday 09 March 2013 12:11 AM, Stephen Warren wrote:
> On 03/08/2013 11:06 AM, Laxman Dewangan wrote:
> > On Friday 08 March 2013 11:21 PM, Stephen Warren wrote:
> > > On 03/08/2013 06:52 AM, Laxman Dewangan wrote:
> > > > NVIDIA's Tegra114 has 32 channels APB DMA controller. Add DT entry for
> > > > APB DMA controllers and make it compatible with
> > > > "nvidia,tegra114-apbdma".
> > > > diff --git a/arch/arm/boot/dts/tegra114.dtsi
> > > > b/arch/arm/boot/dts/tegra114.dtsi
> > > > +    apbdma: dma {
> > > > +        compatible = "nvidia,tegra114-apbdma";
> > > So I know that the Tegra114 HW has a new channel-pause feature, which
> > > the driver /can/ use. However, if the driver didn't know about that
> > > feature, and continued to use the global-pause feature, would it still
> > > work fine?
> > >
> > > In other words, is the Tegra114 HW 100% backwards-compatible with the
> > > Tegra30 HW, it's just that there are new features that SW could
> > > optionally use?
> > >
> > > If that is true, then we should also include "nvidia,tegra30-apbdma" in
> > > the compatible value.
> > Tegra114 HW is not compatible with the tegra30 as with global pause, it
> > is not able to write into the dma register in T114. On t114, the dma
> > register is clock gated with global enable/disable.
> Interesting. In that case, the compatible value above is entirely
> correct. Thanks for the explanation. It might be worth mentioning this
> in the commit description.

I can describe here as I am going to respin the patches anyhow.
However, I have already explain this in the driver commit when porting 
for T114.


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