linux-kernel - Re: [PATCH 2/4] drm: Add DT bindings documentation for ARC PGU display controller

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Date:	Thu, 3 Mar 2016 13:58:18 +0000
From:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:	"robh@...nel.org" <robh@...nel.org>
CC:	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"linux-snps-arc@...ts.infradead.org" 
	<linux-snps-arc@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/4] drm: Add DT bindings documentation for ARC PGU
 display controller

Hi Rob,

On Tue, 2016-02-23 at 14:38 -0600, Rob Herring wrote:
> On Fri, Feb 19, 2016 at 04:03:52PM +0300, Alexey Brodkin wrote:
> > 
> > This add DT bindings documentation for ARC PGU display controller.
> > 
> > Signed-off-by: Alexey Brodkin <abrodkin@...opsys.com>
> > Cc: Rob Herring <robh+dt@...nel.org>
> > Cc: Pawel Moll <pawel.moll@....com>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: Ian Campbell <ijc+devicetree@...lion.org.uk>
> > Cc: Kumar Gala <galak@...eaurora.org>
> > Cc: devicetree@...r.kernel.org
> > Cc: linux-snps-arc@...ts.infradead.org
> > ---
> >  .../devicetree/bindings/display/snps,arcpgu.txt    | 74 ++++++++++++++++++++++
> >  1 file changed, 74 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/snps,arcpgu.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/display/snps,arcpgu.txt
> > b/Documentation/devicetree/bindings/display/snps,arcpgu.txt
> > new file mode 100644
> > index 0000000..c8382fb
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/snps,arcpgu.txt
> > @@ -0,0 +1,74 @@
> > +ARC PGU
> > +
> > +This is a display controller found on several development boards produced
> > +by Synopsys. The ARC PGU is an RGB streamer that reads the data from a
> > +framebuffer and sends it to a single digital encoder (usually HDMI).
> > +
> > +Required properties:
> > +  - compatible: "snps,arcpgu"
> Seems like this should be more specific. Is there some sort or 
> versioning with ARC blocks?

Well as of today there's only one and only version of PGU.
So is there a real need for "snps,arcpgu-1.0"?

> > 
> > +  - reg: Physical base address and length of the controller's registers.
> > +  - clocks: A list of phandle + clock-specifier pairs, one for each
> > +    entry in 'clock-names'.
> > +  - clock-names: A list of clock names. For ARC PGU it should contain:
> > +      - "pxlclk" for the clock feeding the output PLL of the controller.
> > +  - encoder-slave: Phandle of encoder chip.
> This is unnecessary with the OF graph.

Do you mean I may drop "encoder-slave" from bindings description?
I actually thought about that because in case of simulation platform where
this device is also used there's no encoder as well as no connector - we're
dealing with memory area which is read by host and then displayed on host's
display.

> > +
> > +/ {
> > +	...
> > +
> > +	pgu@...XXXXXXX {
> Unit address should not have '0x'

Correct, let me fix it.

> > +
> > +	/* HDMI encoder on I2C bus */
> > +	i2c@...XXXXXXX {
> > +		compatible = "...";
> > +
> > +		encoder_node:encoder_node@...XXXXXXX{
> I2C addresses would be 8-bit only.

Indeed - copy-paste is evil :)

-Alexey