rk3399 issue: no DMA in Linux with mainline TF-A and U-Boot SPL

[Russell King (Oracle)]

On Mon, Apr 03, 2023 at 12:11:40PM +0200, Christoph Fritz wrote:
> > 
> >      The ARM PL330 DMA driver in kernel only relate to:
> > 
> > - DTS kernel used, can be check in /proc/device-tree/
> > 
> > - kernel driver which should mach the compatible name.
> 
> drivers/dma/pl330.c needs also a successfully matched amba, but this
> fails when using mainline TF-A and U-Boot SPL.
> 
> I'm using the same kernel and devicetree on both tests, the only thing
> changed is TF-A and U-Boot SPL   vs   mini-loader and rk3399_bl31.
> 
> > This driver should has nothing to do with U-Boot SPL or TF-A, because we 
> > don't have any special setting for PL330 in loader stage.
> 
> It is drivers/amba/bus.c, which is unable to find an AMBA_CID on the
> ARM bus. The DMA driver not loading is just a symptom of this issue.

That brings up the obvious question: why is it unable to find the AMBA
CID? Is that because some resource needed to read it hasn't been
enabled yet? If the AMBA CID is not accessible, presumably the rest of
the PL330 also isn't accessible, so even if we could bind the driver,
it still wouldn't work?

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