Date:   Wed, 16 Aug 2017 23:46:53 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Rob Herring <robh@...nel.org>
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

Hi,

Dne četrtek, 10. avgust 2017 ob 02:21:21 CEST je Rob Herring napisal(a):
> 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.

Actually, there are more combinations since different SoCs have also different 
capabilities regarding mixer0 or mixer1.

For example, mixer0 on H3 has different capabilities than mixer0 on A83T (max. 
plane size and number and type of planes, etc.).

Best regards,
Jernej

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