On Fri, Jan 4, 2019 at 8:53 PM Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> wrote: > > On Fri, Jan 04, 2019 at 08:39:34PM -0800, John Stultz wrote: > > On Fri, Jan 4, 2019 at 8:00 PM Manivannan Sadhasivam > > <manivannan.sadhasivam@xxxxxxxxxx> wrote: > > > > > > Hi John, > > > > > > On Fri, Jan 04, 2019 at 12:56:22PM -0800, John Stultz wrote: > > > > Some dma channels can be reserved for secure mode or other > > > > hardware on the SoC, so provide a binding for a bitmask > > > > listing the available channels for the kernel to use. > > > > > > > > Cc: Vinod Koul <vkoul@xxxxxxxxxx> > > > > Cc: Rob Herring <robh+dt@xxxxxxxxxx> > > > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > > > Cc: Tanglei Han <hantanglei@xxxxxxxxxx> > > > > Cc: Zhuangluan Su <suzhuangluan@xxxxxxxxxxxxx> > > > > Cc: Ryan Grachek <ryan@xxxxxxxxx> > > > > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> > > > > Cc: dmaengine@xxxxxxxxxxxxxxx > > > > Cc: devicetree@xxxxxxxxxxxxxxx > > > > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> > > > > --- > > > > Documentation/devicetree/bindings/dma/k3dma.txt | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/Documentation/devicetree/bindings/dma/k3dma.txt b/Documentation/devicetree/bindings/dma/k3dma.txt > > > > index 10a2f15..1c466c1 100644 > > > > --- a/Documentation/devicetree/bindings/dma/k3dma.txt > > > > +++ b/Documentation/devicetree/bindings/dma/k3dma.txt > > > > @@ -14,6 +14,9 @@ Required properties: > > > > have specific request line > > > > - clocks: clock required > > > > > > > > +Optional properties: > > > > +- dma-avail-chan: Bitmask of available physical channels > > > > + > > > > > > This property looks too generic. Since this is specific to HiSi SoCs, > > > this could be "hisi-dma-avail-chan"? > > > > I'm fine to change it, but I'm not sure I fully understand the > > rational. Can you help me understand? > > Are device node-binding names supposed to have global scope? I assumed > > the node property names are basically scoped to the entry? > > IIUC properties documented in subsystem binding (dma.txt in this case) > will have global scope. Those which are not documented in this binding > are specific to vendor IPs and should be prefixed with the vendor > prefix (hisi in this case). Thanks I appreciate the explanation here. I hadn't really understood this point, and really haven't developed much "taste" in what makes a good or bad binding. > > Further, having some dma channels be reserved doesn't seem to be too > > unique a concept, so I'm not sure what we gain long term by prefixing > > it? > > > > Right, but this brings up the point of having this functionality in > generic DMA engine so that the DMA controller drivers need not handle. > So either we should move this available channel check to DMA Engine > and document the property in dma.txt so that other IPs can also use it > or keep the functionality in K3 driver and use HiSi prefix for the > property. > > But I'd like to hear Vinod/Rob's opinion on this! Sure. Though for now I'll prefix it as the logic is handled at the driver level. thanks -john
