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

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Date:   Wed,  3 Aug 2022 09:24:21 +0800
From:   Liu Ying <victor.liu@....com>
To:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     robh+dt@...nel.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: [PATCH v2 3/3] dt-bindings: bus: Add Freescale i.MX8qxp pixel link MSI bus binding

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
+---
+$id: http://devicetree.org/schemas/bus/fsl,imx8qxp-pixel-link-msi-bus.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+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
+
+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