On Tue, 15 Oct 2019 at 15:18, Russell King - ARM Linux admin
<linux@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Oct 15, 2019 at 03:12:49PM +0200, Christian Zigotzky wrote:
> > Hello Russell,
> >
> > You asked me about "dma-coherent" in the Cyrus device tree. Unfortunately I
> > don't find the property "dma-coherent" in the dtb source files.
> >
> > Output of "fdtdump cyrus_p5020_eth_poweroff.dtb | grep dma":
> >
> > dma0 = "/soc@ffe000000/dma@100300";
> > dma1 = "/soc@ffe000000/dma@101300";
> > dma@100300 {
> > compatible = "fsl,eloplus-dma";
> > dma-channel@0 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@80 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@100 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@180 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma@101300 {
> > compatible = "fsl,eloplus-dma";
> > dma-channel@0 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@80 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@100 {
> > compatible = "fsl,eloplus-dma-channel";
> > dma-channel@180 {
> > compatible = "fsl,eloplus-dma-channel";
>
> Hmm, so it looks like PowerPC doesn't mark devices that are dma
> coherent with a property that describes them as such.
>
> I think this opens a wider question - what should of_dma_is_coherent()
> return for PowerPC? It seems right now that it returns false for
> devices that are DMA coherent, which seems to me to be a recipe for
> future mistakes.
Perhaps implement the arch_setup_dma_ops() for PPC, that set
"dev->dma_coherent = true" could work?
[...]
Kind regards
Uffe
