Re: [PATCH 06/11] dt-bindings: display: sun4i-drm: Add A83T HDMI pipeline

[Jernej Åkrabec]

Hi Rob,

Dne sreda, 03. januar 2018 ob 21:21:54 CET je Rob Herring napisal(a):
> On Sat, Dec 30, 2017 at 10:01:58PM +0100, Jernej Skrabec wrote:
> > This commit adds all necessary compatibles and descriptions needed to
> > implement A83T HDMI pipeline.
> > 
> > Mixer is already properly described, so only compatible is added.
> > 
> > However, A83T TCON1, which is connected to HDMI, doesn't have channel 0,
> > contrary to all TCONs currently described. Because of that, TCON
> > documentation is extended.
> > 
> > A83T features Synopsys DW HDMI controller with a custom PHY which looks
> > like Synopsys Gen2 PHY with few additions. Since there is no
> > documentation, needed properties were found out through experimentation
> > and reading BSP code.
> > 
> > At the end, example is added for newer SoCs, which features DE2 and DW
> > HDMI.
> > 
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
> > ---
> > 
> >  .../bindings/display/sunxi/sun4i-drm.txt           | 188
> >  ++++++++++++++++++++- 1 file changed, 181 insertions(+), 7 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt index
> > 9f073af4c711..3eca258096a5 100644
> > --- a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > +++ b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
> > 
> > @@ -64,6 +64,40 @@ Required properties:
> >      first port should be the input endpoint. The second should be the
> >      output, usually to an HDMI connector.
> > 
> > +DWC HDMI TX Encoder
> > +-----------------------------
> > +
> > +The HDMI transmitter is a Synopsys DesignWare HDMI 1.4 TX controller IP
> > +with Allwinner's own PHY IP. It supports audio and video outputs and CEC.
> > +
> > +These DT bindings follow the Synopsys DWC HDMI TX bindings defined in
> > +Documentation/devicetree/bindings/display/bridge/dw_hdmi.txt with the
> > +following device-specific properties.
> > +
> > +Required properties:
> > +
> > +  - compatible: value must be one of:
> > +    * "allwinner,sun8i-a83t-dw-hdmi"
> > +  - reg: two pairs of base address and size of memory-mapped region,
> > first
> > +    for controller and second for PHY
> > +    registers.
> 
> Seems like the phy should be a separate node and use the phy binding.
> You can use the phy binding even if you don't use the kernel phy
> framework...

Unfortunately, it's not so straighforward. Phy is actually accessed through 
I2C implemented in HDMI controller. Second memory region in this case has 
small influence on phy. However, it has big influence on controller. For 
example, magic number has to be written in one register in second memory 
region in order to unlock read access to any register from first memory region 
(controller). However, they shouldn't be merged to one region, because first 
memory region requires byte access while second memory region can be accessed 
per byte or word.

To complicate things more, later I want to add support for another SoC which 
has same glue layer (unlocking read access, etc.) and uses memory mapped phy 
registers in second memory region.

I think current binding is the least complicated way to represent this.

> 
> > +  - reg-io-width: See dw_hdmi.txt. Shall be 1.
> > +  - interrupts: HDMI interrupt number
> > +  - clocks: phandles to the clocks feeding the HDMI encoder
> > +    * iahb: the HDMI bus clock
> > +    * isfr: the HDMI register clock
> > +    * tmds: the HDMI tmds clock
> > +  - clock-names: the clock names mentioned above
> > +  - resets: phandles to the reset controllers driving the encoder
> > +    * ctrl: the reset line for the controller
> > +    * phy: the reset line for the PHY
> > +  - reset-names: the reset names mentioned above
> > +
> > +  - ports: A ports node with endpoint definitions as defined in
> > +    Documentation/devicetree/bindings/media/video-interfaces.txt. The
> > +    first port should be the input endpoint. The second should be the
> > +    output, usually to an HDMI connector.
> > +
> > 
> >  TV Encoder
> >  ----------
> > 
> > @@ -94,18 +128,17 @@ Required properties:
> >     * allwinner,sun7i-a20-tcon
> >     * allwinner,sun8i-a33-tcon
> >     * allwinner,sun8i-a83t-tcon-lcd
> > 
> > +   * allwinner,sun8i-a83t-tcon-tv
> > 
> >     * 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:
> > 
> > + - clocks: phandles to the clocks feeding the TCON. One is 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
> > 
> > @@ -119,11 +152,31 @@ 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:
> > +Following compatibles:
> > + * allwinner,sun4i-a10-tcon
> > + * allwinner,sun5i-a13-tcon
> > + * allwinner,sun6i-a31-tcon
> > + * allwinner,sun6i-a31s-tcon
> > + * allwinner,sun7i-a20-tcon
> > + * allwinner,sun8i-a33-tcon
> > + * allwinner,sun8i-a83t-tcon-lcd
> > + * allwinner,sun8i-v3s-tcon
> > +have additional required properties:
> > + - 'tcon-ch0': The clock driving the TCON channel 0
> 
> tcon-ch0 is a clock name, not a property.

right.

Best regards,
Jernej