linux-kernel - Re: [RFC PATCH 3/3] dt-bindings: display: add Amlogic Meson DRM Bindings

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Message-ID: <1695441.JP1H7VIm1f@avalon>
Date:   Mon, 28 Nov 2016 12:02:57 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     dri-devel@...ts.freedesktop.org, airlied@...ux.ie,
        khilman@...libre.com, carlo@...one.org, devicetree@...r.kernel.org,
        Xing.Xu@...ogic.com, victor.wan@...ogic.com,
        linux-kernel@...r.kernel.org, jerry.cao@...ogic.com,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 3/3] dt-bindings: display: add Amlogic Meson DRM Bindings

Hi Neil,

On Monday 28 Nov 2016 10:56:30 Neil Armstrong wrote:
> On 11/28/2016 10:37 AM, Laurent Pinchart wrote:
> > On Monday 28 Nov 2016 10:23:43 Neil Armstrong wrote:
> >> On 11/28/2016 09:33 AM, Laurent Pinchart wrote:
> >>> On Friday 25 Nov 2016 17:03:11 Neil Armstrong wrote:
> >>>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> >>>> ---
> >>>> 
> >>>>  .../bindings/display/meson/meson-drm.txt           | 134
> >>>>  +++++++++++++++
> >>>>  1 file changed, 134 insertions(+)
> >>>>  create mode 100644
> >>>> 
> >>>> Documentation/devicetree/bindings/display/meson/meson-drm.txt
> >>>> 
> >>>> diff --git
> >>>> a/Documentation/devicetree/bindings/display/meson/meson-drm.txt
> >>>> b/Documentation/devicetree/bindings/display/meson/meson-drm.txt new
> >>>> file
> >>>> mode 100644
> >>>> index 0000000..89c1b5f
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/display/meson/meson-drm.txt
> 
> [...]
> 
> >>>> +
> >>>> +VENC CBVS Output
> >>>> +----------------------
> >>>> +
> >>>> +The VENC can output Composite/CVBS output via a decicated VDAC.
> >>>> +
> >>>> +Required properties:
> >>>> +  - compatible: value must be one of:
> >>>> + - compatible: value should be different for each SoC family as :
> >>> One of those two lines is redundant.
> >> 
> >> Will fix.
> >> 
> >>>> + 	- GXBB (S905) : "amlogic,meson-gxbb-venc-cvbs"
> >>>> + 	- GXL (S905X, S905D) : "amlogic,meson-gxl-venc-cvbs"
> >>>> + 	- GXM (S912) : "amlogic,meson-gxm-venc-cvbs"
> >>>> +	followed by the common "amlogic,meson-gx-venc-cvbs"
> >>>> +
> >>> 
> >>> No registers ? Are the encoders registers part of the VPU register
> >>> space, intertwined in a way that they can't be specified separately here
> >>> ?
> >> 
> >> Exact, all the video registers on the Amlogic SoC are part of a long
> >> history of fixup/enhance from very old SoCs, it's quite hard to
> >> distinguish a Venc registers array since they are mixed with the
> >> multiple encoders registers...
> > 
> > In that case is there really a reason to model the encoders as separate
> > nodes in DT ?
> 
> Here, it more the encoder-connector couple that is represented as a node,
> and the CVBS output is optional.

You should actually have a DT node for the connector. I would merge the 
encoders into the VPU node (especially given that according to your diagram 
they are part of the VPU), and document the VPU output ports explicitly. If 
the CVBS output is not implemented by some of the SoCs in the family then the 
corresponding DT node should just omit that port.

> >> The only separate registers are the VDAC and HDMI PHY, I may move them to
> >> these separate nodes since they are part of the HHI register space.
> >> 
> >> It is a problem if I move them in the next release ? Next release will
> >> certainly have HDMI support, and will have these refactorings.
> > 
> > Given that DT bindings are considered as a stable ABI, I'm afraid it's an
> > issue.
> 
> OK, I will add the VDAC/HDMI PHY registers as part if these output nodes.

Thank you.

> >>>> +- ports: A ports node with endpoint definitions as defined in
> >>>> +  Documentation/devicetree/bindings/media/video-interfaces.txt. The
> >>>> +  first port should be the input endpoints, connected ot the VPU node.
> >>>> +
> >>>> +Example:
> >>>> +
> >>>> +venc_cvbs: venc-cvbs {
> >>>> +	compatible = "amlogic,meson-gxbb-venc-cvbs";
> >>>> +	status = "okay";
> >>>> +
> >>>> +	ports {
> >>>> +		#address-cells = <1>;
> >>>> +		#size-cells = <0>;
> >>>> +
> >>>> +		enc_cvbs_in: port@0 {
> >>>> +			 #address-cells = <1>;
> >>>> +			 #size-cells = <0>;
> >>>> +			 reg = <0>;
> >>>> +
> >>>> +			 venc_cvbs_in_vpu: endpoint@0 {
> >>>> +				 reg = <0>;
> >>>> +				 remote-endpoint = 
<&vpu_out_venc_cvbs>;
> >>>> +			};
> >>>> +		};
> >>>> +	};
> >>>> +};
> >>>> +
> >>>> +vpu: vpu@...00000 {
> >>>> +	compatible = "amlogic,meson-gxbb-vpu";
> >>>> +	reg = <0x0 0xd0100000 0x0 0x100000>,
> >>>> +	      <0x0 0xc883c000 0x0 0x1000>,
> >>>> +	      <0x0 0xc8838000 0x0 0x1000>;
> >>>> +	reg-names = "base", "hhi", "dmc";
> >>>> +	interrupts = <GIC_SPI 3 IRQ_TYPE_EDGE_RISING>;
> >>>> +
> >>>> +	ports {
> >>>> +		#address-cells = <1>;
> >>>> +		#size-cells = <0>;
> >>>> +
> >>>> +		vpu_out: port@1 {
> >>>> +			 #address-cells = <1>;
> >>>> +			 #size-cells = <0>;
> >>>> +			 reg = <1>;
> >>>> +
> >>>> +			 vpu_out_venc_cvbs: endpoint@0 {
> >>>> +				 reg = <0>;
> >>>> +				 remote-endpoint = 
<&venc_cvbs_in_vpu>;
> >>>> +			 };
> >>>> +		 };
> >>>> +	};
> >>>> +};
> >> 
> >> Thanks for the review !

-- 
Regards,

Laurent Pinchart