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

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Date:   Thu, 19 Apr 2018 16:55:10 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com,
        "Signed-off-by : Bob Ham" <rah@...trans.net>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Florent Revest <revestflo@...il.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Icenowy Zheng <icenowy@...c.xyz>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Thomas van Kleef <thomas@...sch.nl>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH 6/9] sunxi-cedrus: Add device tree binding document

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@...e-electrons.com>
> 
> "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@...e-electrons.com>
> > ---
> >  .../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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