On Mon, Oct 26, 2026 at 11:51:11AM +0530, Jayant Shekhar wrote:
> DCP platforms place the display pipeline under firmware control, so Linux
> cannot discover display resources through direct register access. The DRM
> driver therefore needs device-tree descriptions of the Qualcomm transport
> wrapper, display topology, IOMMU contexts, and panel connections.
>
> Add bindings for the Qualcomm DCP transport wrapper and VirtIO display
> subsystem. Document the IPCC power-notify resources, transport and
> framebuffer IOMMU contexts, firmware-visible IOVA range, INTF graph, and
> DSI panel connections. The wrapper creates a standard VirtIO-MMIO child
> after the IPCC power-notify sequence has completed.
>
> Assisted-by: LLM
> Signed-off-by: Jayant Shekhar <[email protected]>
> ---
> .../bindings/display/msm/qcom,dcp-dsi.yaml | 79 ++++++++++++
> .../devicetree/bindings/display/msm/qcom,dcp.yaml | 123 +++++++++++++++++++
> .../bindings/virtio/qcom,dcp-virtio.yaml | 132
> +++++++++++++++++++++
> 3 files changed, 334 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/msm/qcom,dcp-dsi.yaml
> b/Documentation/devicetree/bindings/display/msm/qcom,dcp-dsi.yaml
> new file mode 100644
> index 000000000000..9a0acaf00bb3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/msm/qcom,dcp-dsi.yaml
> @@ -0,0 +1,79 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/msm/qcom,dcp-dsi.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm DCP DSI host
> +
> +maintainers:
> + - Jayant Shekhar <[email protected]>
> +
> +description: |
> + A MIPI DSI host exposed by the Qualcomm DCP VirtIO device (see
> + qcom,dcp.yaml). It follows the generic DSI controller binding, with panel
> + devices described as child nodes. The DCP INTF graph endpoint connects
> + directly to the panel; the DSI host node is not a graph endpoint. The host
> + node uses the dsi@N naming convention, and its reg property identifies the
> + DSI host index.
> +
> +allOf:
> + - $ref: /schemas/display/dsi-controller.yaml#
If there are no separate compatibles, can this be folded into the main
DCP schema?
> +
> +properties:
> + reg:
> + maxItems: 1
> + description: DSI host index matching the DCP output port.
> +
> +required:
> + - reg
> + - "#address-cells"
> + - "#size-cells"
> +
> +unevaluatedProperties: false
> +
> +examples:
> + - |
> + #include <dt-bindings/gpio/gpio.h>
> +
> + dcp-subsystem {
> + compatible = "virtio,device34";
> + iommus = <&apps_smmu 0x400 0x2>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ports {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + port@0 {
> + reg = <0>;
> + dcp_intf0_out: endpoint {
> + remote-endpoint = <&panel_dcp_in>;
> + };
> + };
> + };
> +
> + dsi@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
Yes, fold it there. It's not a separate device on its own.
> +
> + panel@0 {
> + compatible = "novatek,nt37801";
> + reg = <0>;
> +
> + vddio-supply = <&vreg_l12b_1p8>;
> + vci-supply = <&vreg_l13b_3p0>;
> + vdd-supply = <&display_panel_vdd>;
> + reset-gpios = <&tlmm 210 GPIO_ACTIVE_LOW>;
> +
> + port {
> + panel_dcp_in: endpoint {
> + remote-endpoint = <&dcp_intf0_out>;
> + };
> + };
> + };
> + };
> + };
> diff --git a/Documentation/devicetree/bindings/display/msm/qcom,dcp.yaml
> b/Documentation/devicetree/bindings/display/msm/qcom,dcp.yaml
> new file mode 100644
> index 000000000000..96f6c2a17e9e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/msm/qcom,dcp.yaml
> @@ -0,0 +1,123 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/msm/qcom,dcp.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Display Co-Processor (DCP)
> +
> +maintainers:
> + - Jayant Shekhar <[email protected]>
> +
> +description: |
> + The Display Co-Processor (DCP) is a firmware-owned display subsystem.
> + Linux communicates with DCP over HFI through VirtIO and does not access
> + display hardware registers directly.
> +
> + This node describes the externally connected display graph between DCP
> + INTF outputs and attached DSI panels. It is assigned to the VirtIO device
> + by the Qualcomm transport driver and is not independently enumerated.
> + Firmware capabilities and internal resources, including pipes, mixers,
> + CRTCs, and clocks, are discovered at runtime.
> +
> +allOf:
> + - $ref: /schemas/virtio/virtio-device.yaml#
> +
> +properties:
> + compatible:
> + const: virtio,device34
> +
> + iommus:
> + maxItems: 1
> + description:
> + SMMU context used by DCP firmware to access GEM framebuffers. This
> + is separate from the HFI transport context specified by the
> + iommus property on the parent DCP transport node.
> + The child context is used for framebuffer DMA performed by DCP
> + firmware, while the parent context is used for VirtIO transport and HFI
> + queue buffers. These contexts represent distinct firmware-visible DMA
> + address spaces and must not be used interchangeably.
> +
> + "#address-cells":
> + const: 1
> +
> + "#size-cells":
> + const: 0
> +
> + ports:
> + $ref: /schemas/graph.yaml#/properties/ports
> + description: |
> + DPU INTF output-only ports. The port number matches the firmware INTF
> + index. The corresponding DSI host is the child node whose reg value
> + matches the port number; the graph endpoint itself connects directly to
> + the attached panel. Unused INTF ports are omitted.
> + unevaluatedProperties: false
> + patternProperties:
> + "^port@[0-9a-f]+$":
> + $ref: /schemas/graph.yaml#/$defs/port-base
> + unevaluatedProperties: false
> + properties:
> + endpoint:
> + $ref: /schemas/graph.yaml#/$defs/endpoint-base
> + unevaluatedProperties: false
> + required:
> + - remote-endpoint
> +
> +patternProperties:
> + "^dsi@[0-9a-f]+$":
> + $ref: qcom,dcp-dsi.yaml#
When adding DP support, would you add more devices at the same level? If
so, we risk getting a warning about multiple devices using the same
address.
> +required:
> + - compatible
> + - iommus
> + - "#address-cells"
> + - "#size-cells"
> + - ports
> +
> +unevaluatedProperties: false
> +
> +examples:
> + - |
> + #include <dt-bindings/gpio/gpio.h>
> +
> + dcp-subsystem {
> + compatible = "virtio,device34";
> + iommus = <&apps_smmu 0x400 0x2>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ports {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + port@0 {
> + reg = <0>;
> + dcp_intf0_out: endpoint {
> + remote-endpoint = <&panel_dcp_in>;
> + };
> + };
> + };
> +
> + dsi@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + panel@0 {
> + compatible = "novatek,nt37801";
> + reg = <0>;
> +
> + vddio-supply = <&vreg_l12b_1p8>;
> + vci-supply = <&vreg_l13b_3p0>;
> + vdd-supply = <&display_panel_vdd>;
> + reset-gpios = <&tlmm 210 GPIO_ACTIVE_LOW>;
> +
> + port {
> + panel_dcp_in: endpoint {
> + remote-endpoint = <&dcp_intf0_out>;
> + };
> + };
> + };
> + };
> + };
> diff --git a/Documentation/devicetree/bindings/virtio/qcom,dcp-virtio.yaml
> b/Documentation/devicetree/bindings/virtio/qcom,dcp-virtio.yaml
> new file mode 100644
> index 000000000000..6020e848ce25
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/virtio/qcom,dcp-virtio.yaml
> @@ -0,0 +1,132 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/virtio/qcom,dcp-virtio.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm DCP VirtIO transport
> +
> +maintainers:
> + - Jayant Shekhar <[email protected]>
> +
> +description: |
> + Qualcomm DCP VirtIO transport. The IPCC power-notify channel and
> + associated interrupts are required before the transport can access its
> + MMIO registers. This is a Qualcomm-specific transport and must not use the
> + generic virtio-mmio driver. The DCP VirtIO function is described as a child
> + node and is assigned to the registered VirtIO device by this transport.
> +
> +properties:
> + compatible:
> + const: qcom,dcp-virtio
> +
> + reg:
> + maxItems: 1
> +
> + interrupts-extended:
> + minItems: 2
> + maxItems: 2
> + description: The VirtIO-MMIO and DCP power-notify interrupts, in that
> order.
> +
> + iommus:
> + maxItems: 1
> +
> + iommu-ranges:
> + $ref: /schemas/types.yaml#/definitions/uint32-array
> + description: |
> + The firmware-visible IOVA range, specified as a four-cell tuple
> + containing a 64-bit IOVA base followed by a 64-bit range size.
> + items:
> + - description: IOVA base, high cell
> + $ref: /schemas/types.yaml#/definitions/uint32
> + - description: IOVA base, low cell
> + $ref: /schemas/types.yaml#/definitions/uint32
> + - description: IOVA range size, high cell
> + $ref: /schemas/types.yaml#/definitions/uint32
> + - description: IOVA range size, low cell
> + $ref: /schemas/types.yaml#/definitions/uint32
> +
> + dma-coherent: true
> +
> + mboxes:
> + maxItems: 1
> +
> + mbox-names:
> + const: dcp-power-tx
> +
> + dcp-subsystem:
'dcp' is not a generic name. If you want to list it here, it should be
something like 'display-subsystem' or 'display-controller'.
> + $ref: ../display/msm/qcom,dcp.yaml#
> +
> +required:
> + - compatible
> + - reg
> + - interrupts-extended
> + - iommus
> + - iommu-ranges
> + - dma-coherent
> + - mboxes
> + - mbox-names
> + - dcp-subsystem
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + #include <dt-bindings/gpio/gpio.h>
> + #include <dt-bindings/interrupt-controller/arm-gic.h>
> + #include <dt-bindings/interrupt-controller/irq.h>
> + #include <dt-bindings/mailbox/qcom-ipcc.h>
> +
> + virtio@9be8000 {
> + compatible = "qcom,dcp-virtio";
> + reg = <0x09be8000 0x1000>;
> + interrupts-extended = <&intc GIC_ESPI 956 IRQ_TYPE_LEVEL_HIGH>,
> + <&ipcc 13 5 IRQ_TYPE_EDGE_RISING>;
> + iommus = <&apps_smmu 0x15a3 0x0>;
> + iommu-ranges = <0x0 0x84000000 0x0 0x04000000>;
This doesn't match the address / size cells.
> + dma-coherent;
> + mboxes = <&ipcc 13 5>;
> + mbox-names = "dcp-power-tx";
> +
> + dcp-subsystem {
> + compatible = "virtio,device34";
> + iommus = <&apps_smmu 0x400 0x2>;
> +
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + ports {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + port@0 {
> + reg = <0>;
> + dcp_intf0_out: endpoint {
> + remote-endpoint = <&panel_dcp_in>;
> + };
> + };
> + };
> +
> + dsi@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + panel@0 {
> + compatible = "novatek,nt37801";
> + reg = <0>;
> +
> + vddio-supply = <&vreg_l12b_1p8>;
> + vci-supply = <&vreg_l13b_3p0>;
> + vdd-supply = <&display_panel_vdd>;
> + reset-gpios = <&tlmm 210 GPIO_ACTIVE_LOW>;
> +
> + port {
> + panel_dcp_in: endpoint {
> + remote-endpoint = <&dcp_intf0_out>;
> + };
> + };
> + };
> + };
> + };
> + };
>
> --
> 2.43.0
>
--
With best wishes
Dmitry
