Re: [PATCH 6/9] sunxi-cedrus: Add device tree binding document

From: Paul Kocialkowski
Date: Thu Apr 19 2018 - 10:56:33 EST


Hi,

On Sun, 2018-03-18 at 07:48 -0500, Rob Herring wrote:
> On Fri, Mar 09, 2018 at 11:14:42AM +0100, Paul Kocialkowski wrote:
> > From: Florent Revest <florent.revest@xxxxxxxxxxxxxxxxxx>
>
> "device tree binding document" can all be summarized with the subject
> prefix "dt-bindings: media: ".

Will do in v2, thanks.

> Also, email should be updated to @bootlin.com?

I will keep the address @free-electrons.com (since there is no matching
@bootlin.com address). Although that address was broken at the time of
sending v1, it should be a valid redirect nowadays.

> >
> > Device Tree bindings for the Allwinner's video engine
> >
> > Signed-off-by: Florent Revest <florent.revest@xxxxxxxxxxxxxxxxxx>
> > ---
> > .../devicetree/bindings/media/sunxi-cedrus.txt | 44
> > ++++++++++++++++++++++
> > 1 file changed, 44 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/media/sunxi-
> > cedrus.txt
> >
> > diff --git a/Documentation/devicetree/bindings/media/sunxi-
> > cedrus.txt b/Documentation/devicetree/bindings/media/sunxi-
> > cedrus.txt
> > new file mode 100644
> > index 000000000000..138581113c49
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/sunxi-cedrus.txt
> > @@ -0,0 +1,44 @@
> > +Device-Tree bindings for SUNXI video engine found in sunXi SoC
> > family
> > +
> > +Required properties:
> > +- compatible : "allwinner,sun4i-a10-video-engine";
> > +- memory-region : DMA pool for buffers allocation;
>
> Why do you need this linkage? Many drivers use CMA and don't need
> this.

The VPU can only access the first 256 MiB of DRAM, that are DMA-mapped
starting from the DRAM base. This requires specific memory allocation
and handling. I'll add the information in v2.

> > +- clocks : list of clock specifiers, corresponding to
> > + entries in clock-names property;
> > +- clock-names : should contain "ahb", "mod" and "ram"
> > entries;
> > +- resets : phandle for reset;
> > +- interrupts : should contain VE interrupt number;
> > +- reg : should contain register base and length
> > of VE.
> > +
> > +Example:
> > +
> > +reserved-memory {
> > + #address-cells = <1>;
> > + #size-cells = <1>;
> > + ranges;
> > +
> > + ve_reserved: cma {
> > + compatible = "shared-dma-pool";
> > + reg = <0x43d00000 0x9000000>;
> > + no-map;
> > + linux,cma-default;
> > + };
> > +};
> > +
> > +video-engine {
> > + compatible = "allwinner,sun4i-a10-video-engine";
> > + memory-region = <&ve_reserved>;
> > +
> > + clocks = <&ahb_gates 32>, <&ccu CLK_VE>,
> > + <&dram_gates 0>;
> > + clock-names = "ahb", "mod", "ram";
> > +
> > + assigned-clocks = <&ccu CLK_VE>;
> > + assigned-clock-rates = <320000000>;
>
> Not documented.

Will do in v2.

--
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com

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