linux-kernel - Re: [PATCH v2 3/3] dt-bindings: bus: Add Freescale i.MX8qxp pixel link MSI bus binding

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Message-ID: <7310519e9a9684f591bc0d58277ad7715881e192.camel@nxp.com>
Date:   Thu, 04 Aug 2022 13:53:37 +0800
From:   Liu Ying <victor.liu@....com>
To:     Rob Herring <robh@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, krzysztof.kozlowski+dt@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com, saravanak@...gle.com,
        gregkh@...uxfoundation.org, geert+renesas@...der.be,
        krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v2 3/3] dt-bindings: bus: Add Freescale i.MX8qxp pixel
 link MSI bus binding

On Wed, 2022-08-03 at 17:37 -0600, Rob Herring wrote:
> On Wed, Aug 03, 2022 at 09:24:21AM +0800, Liu Ying wrote:
> > Freescale i.MX8qxp pixel link MSI bus is a simple memory-mapped
> > bus.
> > It is used to access peripherals in i.MX8qm/qxp imaging, LVDS, MIPI
> > DSI and HDMI TX subsystems, like I2C controller, PWM controller,
> > MIPI DSI controller and Control and Status Registers (CSR) module.
> > 
> > Reference simple-pm-bus bindings and add Freescale i.MX8qxp pixel
> > link MSI bus specific bindings.
> > 
> > Signed-off-by: Liu Ying <victor.liu@....com>
> > ---
> > v1->v2:
> > Address Krzysztof's comments:
> > * Add a select to explicitly select the MSI bus dt-binding.
> > * List 'simple-pm-bus' explicitly as one item of compatible
> > strings.
> > * Require compatible and reg properties.
> > * Put reg property just after compatible property in example.
> > 
> >  .../bus/fsl,imx8qxp-pixel-link-msi-bus.yaml   | 97
> > +++++++++++++++++++
> >  1 file changed, 97 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/bus/fsl,imx8qxp-pixel-link-msi-
> > bus.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/bus/fsl,imx8qxp-
> > pixel-link-msi-bus.yaml
> > b/Documentation/devicetree/bindings/bus/fsl,imx8qxp-pixel-link-msi-
> > bus.yaml
> > new file mode 100644
> > index 000000000000..358c032041e5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/bus/fsl,imx8qxp-pixel-link-
> > msi-bus.yaml
> > @@ -0,0 +1,97 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: 
> > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fschemas%2Fbus%2Ffsl%2Cimx8qxp-pixel-link-msi-bus.yaml%23&amp;data=05%7C01%7Cvictor.liu%40nxp.com%7C3ce426916ec64ab9089708da75a92be5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637951666695217514%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=qKEVrlyUkszZ%2FQyYeTIF9AoEqYvCiJjwVTIflzYiyOY%3D&amp;reserved=0
> > +$schema: 
> > https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=05%7C01%7Cvictor.liu%40nxp.com%7C3ce426916ec64ab9089708da75a92be5%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637951666695217514%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=hhwFjqe3xmBtdrbG0EwtpGv%2By3jD%2Bm6OXN3hK6WQw4A%3D&amp;reserved=0
> > +
> > +title: Freescale i.MX8qxp Pixel Link Medium Speed Interconnect
> > (MSI) Bus
> > +
> > +maintainers:
> > +  - Liu Ying <victor.liu@....com>
> > +
> > +description: |
> > +  i.MX8qxp pixel link MSI bus is used to control settings of PHYs,
> > I/Os
> > +  sitting together with the PHYs.  It is not the same as the MSI
> > bus coming
> > +  from i.MX8 System Controller Unit (SCU) which is used to control
> > power,
> > +  clock and reset through the i.MX8 Distributed Slave System
> > Controller (DSC).
> > +
> > +  i.MX8qxp pixel link MSI bus is a simple memory-mapped bus. Two
> > input clocks,
> > +  that is, MSI clock and AHB clock, need to be enabled so that
> > peripherals
> > +  connected to the bus can be accessed. Also, the bus is part of a
> > power
> > +  domain. The power domain needs to be enabled before the
> > peripherals can
> > +  be accessed.
> > +
> > +  Peripherals in i.MX8qm/qxp imaging, LVDS, MIPI DSI and HDMI TX
> > subsystems,
> > +  like I2C controller, PWM controller, MIPI DSI controller and
> > Control and
> > +  Status Registers (CSR) module, are accessed through the bus.
> > +
> > +  The i.MX System Controller Firmware (SCFW) owns and uses the
> > i.MX8qm/qxp
> > +  pixel link MSI bus controller and does not allow SCFW user to
> > control it.
> > +  So, the controller's registers cannot be accessed by SCFW user.
> > Hence,
> > +  the interrupts generated by the controller don't make any sense
> > from SCFW
> > +  user's point of view.
> > +
> > +allOf:
> > +  - $ref: simple-pm-bus.yaml#
> > +
> > +# We need a select here so we don't match all nodes with 'simple-
> > pm-bus'.
> > +select:
> > +  properties:
> > +    compatible:
> > +      contains:
> > +        enum:
> > +          - fsl,imx8qxp-display-pixel-link-msi-bus
> > +          - fsl,imx8qm-display-pixel-link-msi-bus
> > +  required:
> > +    - compatible
> > +
> > +properties:
> > +  compatible:
> > +    items:
> > +      - enum:
> > +          - fsl,imx8qxp-display-pixel-link-msi-bus
> > +          - fsl,imx8qm-display-pixel-link-msi-bus
> > +      - const: simple-pm-bus
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    items:
> > +      - description: master gated clock from system
> > +      - description: AHB clock
> > +
> > +  clock-names:
> > +    items:
> > +      - const: msi
> > +      - const: ahb
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - clocks
> > +  - clock-names
> > +  - power-domains
> > +
> > +unevaluatedProperties: false
> 
> No child nodes allowed?

Should be allowed.

I'll add a pattern property to allow child nodes.

Thanks,
Liu Ying

> 
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/clock/imx8-lpcg.h>
> > +    #include <dt-bindings/firmware/imx/rsrc.h>
> > +    bus@...00000 {
> > +        compatible = "fsl,imx8qxp-display-pixel-link-msi-bus",
> > "simple-pm-bus";
> > +        reg = <0x56200000 0x20000>;
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +        interrupt-parent = <&dc0_irqsteer>;
> > +        interrupts = <320>;
> > +        ranges;
> > +        clocks = <&dc0_disp_ctrl_link_mst0_lpcg IMX_LPCG_CLK_4>,
> > +                 <&dc0_disp_ctrl_link_mst0_lpcg IMX_LPCG_CLK_4>;
> > +        clock-names = "msi", "ahb";
> > +        power-domains = <&pd IMX_SC_R_DC_0>;
> > +    };
> > -- 
> > 2.25.1
> > 
> >