Re: [PATCH] dt-bindings: dma: qcom,bam-dma: add optional memory interconnect properties

[neil . armstrong]

On 08/02/2023 10:03, Krzysztof Kozlowski wrote:
> On 07/02/2023 16:27, Dmitry Baryshkov wrote:
> > On 07/02/2023 15:35, Neil Armstrong wrote:
> > > On 07/02/2023 11:32, Dmitry Baryshkov wrote:
> > > > On 07/02/2023 12:03, Neil Armstrong wrote:
> > > > > Recents SoCs like the SM8450 or SM8550 requires memory interconnect
> > > > > in order to have functional DMA.
> > > > >
> > > > > Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
> > > > > ---
> > > > >    Documentation/devicetree/bindings/dma/qcom,bam-dma.yaml | 6 ++++++
> > > > >    1 file changed, 6 insertions(+)
> > > >
> > > > I suspect this will not work without a change for a driver.
> > >
> > > I had the impression single interconnect entries would be taken in account
> > > by the platform core, but it doesn't seem to be the case, anyway I can;t
> > > find
> > > any code doing that.
> >
> > Probably you mixed interconnects and power-domains here.
>
> The driver change was submitted some time ago:
> https://lore.kernel.org/all/20210505213731.538612-10-bhupesh.sharma@xxxxxxxxxx/
>
> There is already DTS user of it and we expect driver to be resubmitted
> at some point.
>
> What I don't really get is that crypto driver sets bandwidth for
> interconnects, not the BAM. Why BAM needs interconnect? Usually you do
> not need to initialize some middle paths. Getting the final interconnect
> path (e.g. crypto-memory) is enough, because it includes everything in
> between.

Indeed the interconnect on BAM may be redundant since QCE sets the BW,
I'll investigate to understand if it's also necessary on BAM.

Neil

> Maybe my review tag was a bit premature...
>
> Best regards,
> Krzysztof