linux-kernel - Re: [linux-sunxi] [PATCH 01/13] dt-bindings: update the binding for Allwinner H3 DE2 support

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Message-ID: <20170810002121.jydgklyxpm3fuekl@rob-hp-laptop>
Date:   Wed, 9 Aug 2017 19:21:21 -0500
From:   Rob Herring <robh@...nel.org>
To:     Jernej Škrabec <jernej.skrabec@...l.net>
Cc:     linux-sunxi@...glegroups.com, icenowy@...c.io,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [linux-sunxi] [PATCH 01/13] dt-bindings: update the binding for
 Allwinner H3 DE2 support

On Wed, Aug 02, 2017 at 09:06:26PM +0200, Jernej Škrabec wrote:
> Hi,
> 
> Dne sreda, 02. avgust 2017 ob 07:02:39 CEST je icenowy@...c.io napisal(a):
> > 在 2017-08-02 12:53，Jernej Škrabec 写道：
> > 
> > > Hi Icenowy,
> > > 
> > > Dne torek, 01. avgust 2017 ob 15:12:52 CEST je Icenowy Zheng
> > > 
> > > napisal(a):
> > >> Allwinner H3 features a "Display Engine 2.0".
> > >> 
> > >> Add device tree bindings for the following parts:
> > >> - H3 TCONs
> > >> - H3 Mixers
> > >> - H3 Display engine
> > >> 
> > >> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
> > >> ---
> > >> 
> > >>  .../bindings/display/sunxi/sun4i-drm.txt           | 25
> > >> 
> > >> ++++++++++++++++++---- 1 file changed, 21 insertions(+), 4
> > >> deletions(-)
> > >> 
> > >> diff --git
> > >> a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > >> b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt index
> > >> 2ee6ff0ef98e..92512953943e 100644
> > >> --- a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > >> +++ b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > >> 
> > >> @@ -87,18 +87,17 @@ Required properties:
> > >>     * allwinner,sun6i-a31-tcon
> > >>     * allwinner,sun6i-a31s-tcon
> > >>     * allwinner,sun8i-a33-tcon
> > >> 
> > >> +   * allwinner,sun8i-h3-tcon
> > >> 
> > >>     * allwinner,sun8i-v3s-tcon
> > >>   
> > >>   - reg: base address and size of memory-mapped region
> > >>   - interrupts: interrupt associated to this IP
> > >>   
> > >>   - clocks: phandles to the clocks feeding the TCON. Three are needed:
> > >>     - 'ahb': the interface clocks
> > >> 
> > >> -   - 'tcon-ch0': The clock driving the TCON channel 0
> > >> 
> > >>   - resets: phandles to the reset controllers driving the encoder
> > >>   
> > >>     - "lcd": the reset line for the TCON channel 0
> > >>   
> > >>   - clock-names: the clock names mentioned above
> > >>   - reset-names: the reset names mentioned above
> > >> 
> > >> - - clock-output-names: Name of the pixel clock created
> > >> 
> > >>  - ports: A ports node with endpoint definitions as defined in
> > >>  
> > >>    Documentation/devicetree/bindings/media/video-interfaces.txt. The
> > >> 
> > >> @@ -112,7 +111,23 @@ Required properties:
> > >>    channel the endpoint is associated to. If that property is not
> > >>    present, the endpoint number will be used as the channel number.
> > >> 
> > >> -On SoCs other than the A33 and V3s, there is one more clock required:
> > >> +For the following compatibles:
> > >> +   * allwinner,sun5i-a13-tcon
> > >> +   * allwinner,sun6i-a31-tcon
> > >> +   * allwinner,sun6i-a31s-tcon
> > >> +   * allwinner,sun8i-a33-tcon
> > >> +   * allwinner,sun8i-v3s-tcon
> > >> +there is one more clock and one more property required:
> > >> + - clocks:
> > >> +   - 'tcon-ch0': The clock driving the TCON channel 0
> > >> + - clock-output-names: Name of the pixel clock created
> > >> +
> > >> +For the following compatibles:
> > >> +   * allwinner,sun5i-a13-tcon
> > >> +   * allwinner,sun6i-a31-tcon
> > >> +   * allwinner,sun6i-a31s-tcon
> > >> +   * allwinner,sun8i-h3-tcon
> > >> 
> > >> +there is one more clock required:
> > >>     - 'tcon-ch1': The clock driving the TCON channel 1
> > >>  
> > >>  DRC
> > >> 
> > >> @@ -207,6 +222,8 @@ supported.
> > >> 
> > >>  Required properties:
> > >>    - compatible: value must be one of:
> > >>      * allwinner,sun8i-v3s-de2-mixer
> > >> 
> > >> +    * allwinner,sun8i-h3-de2-mixer0
> > >> +    * allwinner,sun8i-h3-de2-mixer1
> > > 
> > > About that, I concur with Maxime here, plane number properties would be
> > > better. If we don't do this now, we will never have it.
> > 
> > But I still prefer different compatibles, as the capabilities are
> > already
> > proven to be different between mixer0 and mixer1, and furtherly we
> > cannot
> > promise Allwinner won't add more functions only available at mixer0.
> > 
> > Then we will be trapped into a situation that we describe more and more
> > functions via properties, but they should be encoded into the
> > compatible.
> 
> It is either multiple compatibles or multiple properties. I prefer the later, 
> but it is up to maintainers to decide.

It's not the same. A compatible can imply an infinite number of 
properties. I'm fine with properties too, but with only 2 instances I 
don't think it makes much sense.

Rob