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Subject: Re: [PATCH 11/14] dt-bindings: display: bridge: Add i.MX8qm/qxp
 LVDS display bridge binding
From:   Liu Ying <victor.liu@nxp.com>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org, airlied@linux.ie, daniel@ffwll.ch,
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        vkoul@kernel.org
Date:   Tue, 22 Dec 2020 16:27:06 +0800
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Hi Laurent,

On Tue, 2020-12-22 at 09:49 +0200, Laurent Pinchart wrote:
> Hi Liu,
> 
> On Tue, Dec 22, 2020 at 09:36:37AM +0200, Laurent Pinchart wrote:
> > On Thu, Dec 17, 2020 at 05:59:30PM +0800, Liu Ying wrote:
> > > This patch adds bindings for i.MX8qm/qxp LVDS display bridge(LDB).
> > > 
> > > Signed-off-by: Liu Ying <victor.liu@nxp.com>
> > > ---
> > >  .../bindings/display/bridge/fsl,imx8qxp-ldb.yaml   | 185 +++++++++++++++++++++
> > >  1 file changed, 185 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/display/bridge/fsl,imx8qxp-ldb.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,imx8qxp-ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,imx8qxp-ldb.yaml
> > > new file mode 100644
> > > index 00000000..4e5ff6f
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/display/bridge/fsl,imx8qxp-ldb.yaml
> > > @@ -0,0 +1,185 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fschemas%2Fdisplay%2Fbridge%2Ffsl%2Cimx8qxp-ldb.yaml%23&amp;data=04%7C01%7Cvictor.liu%40nxp.com%7C3c38a4426c5e40581a1c08d8a64e2e13%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637442201999086534%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=fr9ARb0ct7BDgvzllfXENvJ5KKTLD63PNOaDSkVzqFQ%3D&amp;reserved=0
> > > +$schema: https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=04%7C01%7Cvictor.liu%40nxp.com%7C3c38a4426c5e40581a1c08d8a64e2e13%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637442201999086534%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=LVh6NVTyid8M0%2FDPbBfJQ5%2BhuBxMKw4%2BK9u%2FSIkeaVw%3D&amp;reserved=0
> > > +
> > > +title: Freescale i.MX8qm/qxp LVDS Display Bridge
> > > +
> > > +maintainers:
> > > +  - Liu Ying <victor.liu@nxp.com>
> > > +
> > > +description: |
> > > +  The Freescale i.MX8qm/qxp LVDS Display Bridge(LDB) has two channels.
> > > +
> > > +  For i.MX8qxp LDB, each channel supports up to 24bpp parallel input color
> > > +  format and can map the input to VESA or JEIDA standards.  The two channels
> > > +  cannot be used simultaneously, that is to say, the user should pick one of
> > > +  them to use.  Two LDB channels from two LDB instances can work together in
> > > +  LDB split mode to support a dual link LVDS display.  The channel indexes
> > > +  have to be different.  Channel0 outputs odd pixels and channel1 outputs
> > > +  even pixels.
> > 
> > In this case, does the display controller output odd pixels and even
> > pixels separately to the two LVDS channels, with each channel
> > effectively be a separate LVDS encoder ? Could you give an example of DT
> > integration for dual-link LVDS support, with the display controller, two
> > LDB instances, and a dual-link LVDS panel ?
> 
> I also can't find any mention of the LDB in IMX8MDQLQRM or IMX8DQXPRM.
> Am I missing something ?

i.MX8mq doesn't has LDB.

The i.MX8qxp RM calls LDB as pixel mapper.

This binding calls it 'LDB' for below reasons:
1) 'LDB' is a shorter name.

2) Our internal i.MX8qm/qxp documentations do mention that pixel mapper
uses LDB logic and is based on i.MX6 LDB.

3) Patch 10/14 creates a 'imx-ldb-helper' which can be potentially used
by i.MX6qdl/sx LDBs. So, it will be a consistent name.

Do you think if it will be ok if I mention 'pixel mapper' as a side
note in the next version?

Liu Ying

> 
> > > +
> > > +  For i.MX8qm LDB, each channel additionally supports up to 30bpp parallel
> > > +  input color format.  The two channels can be used simultaneously, either
> > > +  in dual mode or split mode.  In dual mode, the two channels output identical
> > > +  data.  In split mode, channel0 outputs odd pixels and channel1 outputs even
> > > +  pixels.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - fsl,imx8qm-ldb
> > > +      - fsl,imx8qxp-ldb
> > > +
> > > +  "#address-cells":
> > > +    const: 1
> > > +
> > > +  "#size-cells":
> > > +    const: 0
> > > +
> > > +  clocks:
> > > +    items:
> > > +      - description: pixel clock
> > > +      - description: bypass clock
> > > +
> > > +  clock-names:
> > > +    items:
> > > +      - const: pixel
> > > +      - const: bypass
> > > +
> > > +  power-domains:
> > > +    maxItems: 1
> > > +
> > > +  fsl,syscon:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle
> > > +    description: |
> > > +      A phandle which points to Control and Status Registers(CSR) module.
> > > +
> > > +  fsl,companion-ldb:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle
> > > +    description: |
> > > +      A phandle which points to companion LDB which is used in LDB split mode.
> > > +
> > > +patternProperties:
> > > +  "^channel@[0-1]$":
> > > +    type: object
> > > +    description: Represents a channel of LDB.
> > > +
> > > +    properties:
> > > +      "#address-cells":
> > > +        const: 1
> > > +
> > > +      "#size-cells":
> > > +        const: 0
> > > +
> > > +      reg:
> > > +        description: The channel index.
> > > +        enum: [ 0, 1 ]
> > > +
> > > +      phys:
> > > +        description: A phandle to the phy module representing the LVDS PHY.
> > > +        maxItems: 1
> > > +
> > > +      phy-names:
> > > +        const: lvds_phy
> > > +
> > > +      port@0:
> > > +        type: object
> > > +        description: Input port of the channel.
> > > +
> > > +        properties:
> > > +          reg:
> > > +            const: 0
> > > +
> > > +        required:
> > > +          - reg
> > > +
> > > +      port@1:
> > > +        type: object
> > > +        description: Output port of the channel.
> > > +
> > > +        properties:
> > > +          reg:
> > > +            const: 1
> > > +
> > > +        required:
> > > +          - reg
> > > +
> > > +    required:
> > > +      - "#address-cells"
> > > +      - "#size-cells"
> > > +      - reg
> > > +      - phys
> > > +      - phy-names
> > > +
> > > +    additionalProperties: false
> > > +
> > > +required:
> > > +  - compatible
> > > +  - "#address-cells"
> > > +  - "#size-cells"
> > > +  - clocks
> > > +  - clock-names
> > > +  - power-domains
> > > +  - fsl,syscon
> > > +  - channel@0
> > > +  - channel@1
> > > +
> > > +allOf:
> > > +  - if:
> > > +      properties:
> > > +        compatible:
> > > +          contains:
> > > +            const: fsl,imx8qm-ldb
> > > +    then:
> > > +      properties:
> > > +        fsl,companion-ldb: false
> > > +
> > > +additionalProperties: false
> > > +
> > > +examples:
> > > +  - |
> > > +    #include <dt-bindings/firmware/imx/rsrc.h>
> > > +    ldb {
> > > +        #address-cells = <1>;
> > > +        #size-cells = <0>;
> > > +        compatible = "fsl,imx8qxp-ldb";
> > > +        clocks = <&clk IMX_SC_R_LVDS_0 IMX_SC_PM_CLK_MISC2>,
> > > +                 <&clk IMX_SC_R_LVDS_0 IMX_SC_PM_CLK_BYPASS>;
> > > +        clock-names = "pixel", "bypass";
> > > +        power-domains = <&pd IMX_SC_R_LVDS_0>;
> > > +        fsl,syscon = <&mipi_lvds_0_csr>;
> > > +
> > > +        channel@0 {
> > > +            #address-cells = <1>;
> > > +            #size-cells = <0>;
> > > +            reg = <0>;
> > > +            phys = <&mipi_lvds_0_phy>;
> > > +            phy-names = "lvds_phy";
> > > +
> > > +            port@0 {
> > > +                reg = <0>;
> > > +
> > > +                mipi_lvds_0_ldb_ch0_mipi_lvds_0_pxl2dpi: endpoint {
> > > +                    remote-endpoint = <&mipi_lvds_0_pxl2dpi_mipi_lvds_0_ldb_ch0>;
> > > +                };
> > > +            };
> > > +        };
> > > +
> > > +        channel@1 {
> > > +            #address-cells = <1>;
> > > +            #size-cells = <0>;
> > > +            reg = <1>;
> > > +            phys = <&mipi_lvds_0_phy>;
> > > +            phy-names = "lvds_phy";
> > > +
> > > +            port@0 {
> > > +                reg = <0>;
> > > +
> > > +                mipi_lvds_0_ldb_ch1_mipi_lvds_0_pxl2dpi: endpoint {
> > > +                    remote-endpoint = <&mipi_lvds_0_pxl2dpi_mipi_lvds_0_ldb_ch1>;
> > > +                };
> > > +            };
> > > +        };
> > > +    };
> > 
> > -- 
> > Regards,
> > 
> > Laurent Pinchart