arm64: dts: rockchip: add "No Graphics" overlay for RK3576 boards

Add a single DT overlay that disables the display pipeline so it can be
powered down when booting to a headless "No Graphics" target: the VOP
display controller and its IOMMU, the HDMI and DP interfaces and their
PHYs, the HDMI/DP audio cards, and the rockchip-drm display-subsystem
aggregator.

The Mali GPU is deliberately left enabled: a headless system may still
drive a directly-attached panel (e.g. the Flipper One SPI panel, its own
drm/tiny device) whose userspace renders via GLES/EGL, which needs the
GPU. The GPU idles into its own power domain via runtime PM when unused,
so leaving it enabled costs practically nothing.

All disabled nodes are SoC nodes defined in rk3576.dtsi, so one overlay
applies to any RK3576 board; nodes a given board does not enable simply
stay disabled. Overlay-application tests are provided for the EVB1,
ArmSoM Sige5, NanoPi M5, Rock 4D and Flipper One boards.

With these consumers disabled, genpd powers off the PD_VO0 and PD_VO1
domains. PD_VOP is the genpd parent of PD_USB/PD_VO0/PD_VO1, so it stays
powered while USB/UFS are in use - a hardware power-tree constraint; the
VOP controller itself is left unbound and idle.

Panels driven directly over a peripheral bus rather than through the VOP
(e.g. the Flipper One SPI panel) are unaffected and keep working.

Signed-off-by: Yury Smirnov <yurymonzon@gmail.com>

Author: Yury-MonZon

arch/arm64/boot/dts/rockchip/Makefile

@@ -180,6 +180,7 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-khadas-edge-2l.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-luckfox-omni3576.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-nanopi-m5.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-nanopi-r76s.dtb
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-no-graphics.dtbo
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-roc-pc.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-rock-4d.dtb
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3582-radxa-e52c.dtb
@@ -301,6 +302,10 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-armsom-sige5-dp-4k-hdmi-2.5k.dtb
 rk3576-armsom-sige5-dp-4k-hdmi-2.5k-dtbs := rk3576-armsom-sige5.dtb \
 	rk3576-dp-4k-hdmi-2.5k.dtbo
 
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-armsom-sige5-no-graphics.dtb
+rk3576-armsom-sige5-no-graphics-dtbs := rk3576-armsom-sige5.dtb \
+	rk3576-no-graphics.dtbo
+
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-armsom-sige5-v1.2-wifibt.dtb
 rk3576-armsom-sige5-v1.2-wifibt-dtbs := rk3576-armsom-sige5.dtb \
 	rk3576-armsom-sige5-v1.2-wifibt.dtbo
@@ -309,6 +314,10 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-evb1-v10-dp-4k-hdmi-2.5k.dtb
 rk3576-evb1-v10-dp-4k-hdmi-2.5k-dtbs := rk3576-evb1-v10.dtb \
 	rk3576-dp-4k-hdmi-2.5k.dtbo
 
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-evb1-v10-no-graphics.dtb
+rk3576-evb1-v10-no-graphics-dtbs := rk3576-evb1-v10.dtb \
+	rk3576-no-graphics.dtbo
+
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-evb1-v10-pcie1.dtb
 rk3576-evb1-v10-pcie1-dtbs := rk3576-evb1-v10.dtb \
 	rk3576-evb1-v10-pcie1.dtbo
@@ -321,6 +330,10 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-flipper-one-i2c2-free.dtb
 rk3576-flipper-one-i2c2-free-dtbs := rk3576-flipper-one-rev-f0b0c1.dtb \
 	rk3576-flipper-one-i2c2-free.dtbo
 
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-flipper-one-no-graphics.dtb
+rk3576-flipper-one-no-graphics-dtbs := rk3576-flipper-one-rev-f0b0c1.dtb \
+	rk3576-no-graphics.dtbo
+
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-flipper-one-sata.dtb
 rk3576-flipper-one-sata-dtbs := rk3576-flipper-one-rev-f0b0c1.dtb \
 	rk3576-flipper-one-sata.dtbo
@@ -329,6 +342,14 @@ dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-flipper-one-uart2.dtb
 rk3576-flipper-one-uart2-dtbs := rk3576-flipper-one-rev-f0b0c1.dtb \
 	rk3576-flipper-one-uart2.dtbo
 
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-nanopi-m5-no-graphics.dtb
+rk3576-nanopi-m5-no-graphics-dtbs := rk3576-nanopi-m5.dtb \
+	rk3576-no-graphics.dtbo
+
+dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3576-rock-4d-no-graphics.dtb
+rk3576-rock-4d-no-graphics-dtbs := rk3576-rock-4d.dtb \
+	rk3576-no-graphics.dtbo
+
 dtb-$(CONFIG_ARCH_ROCKCHIP) += rk3588-edgeble-neu6a-wifi.dtb
 rk3588-edgeble-neu6a-wifi-dtbs := rk3588-edgeble-neu6a-io.dtb \
 	rk3588-edgeble-neu6a-wifi.dtbo

arch/arm64/boot/dts/rockchip/rk3576-no-graphics.dtso

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * DT-overlay for a "No Graphics" (headless) target on RK3576 boards: disables
+ * the display pipeline so it can be powered down - the VOP display controller
+ * and its IOMMU, the HDMI and DP interfaces and their PHYs, the HDMI/DP audio
+ * cards, and the rockchip-drm display-subsystem aggregator.
+ *
+ * The Mali GPU is deliberately left enabled: a headless system may still drive
+ * a directly-attached panel (e.g. the Flipper One SPI panel, its own drm/tiny
+ * device) whose userspace renders via GLES/EGL, which needs the GPU. The GPU
+ * also idles into its own power domain via runtime PM when unused, so leaving
+ * it enabled costs practically nothing.
+ *
+ * All disabled nodes are SoC nodes defined in rk3576.dtsi, so this single
+ * overlay applies to any RK3576 board. Nodes a given board does not enable stay
+ * disabled - a harmless no-op that also keeps the overlay robust against
+ * stacked overlays.
+ *
+ * With these consumers disabled, genpd powers off the PD_VO0 and PD_VO1 power
+ * domains. Note that PD_VOP is the genpd parent of PD_USB/PD_VO0/PD_VO1, so it
+ * stays powered as long as USB/UFS (children of PD_USB) are in use - a hardware
+ * power-tree constraint. The VOP controller itself is left unbound and idle.
+ *
+ * Panels driven directly over a peripheral bus rather than through the VOP
+ * (e.g. the Flipper One SPI panel) are unaffected and keep working.
+ */
+
+/dts-v1/;
+/plugin/;
+
+&display_subsystem {
+	status = "disabled";
+};
+
+&vop {
+	status = "disabled";
+};
+
+&vop_mmu {
+	status = "disabled";
+};
+
+&hdmi {
+	status = "disabled";
+};
+
+&hdptxphy {
+	status = "disabled";
+};
+
+&hdmi_sound {
+	status = "disabled";
+};
+
+&dp {
+	status = "disabled";
+};
+
+&dp0_sound {
+	status = "disabled";
+};