From b1dcc099d97cedf827a61fa82a717f9fab12e2fd Mon Sep 17 00:00:00 2001
From: Jacob Crowther <3944151+jcrowthe@users.noreply.github.com>
Date: Thu, 12 Nov 2026 23:26:53 -0700
Subject: [PATCH] arm64: dts: apple: t6022-j475d: enable DP alt mode on the
 rear USB-C ports

On the Mac Studio (M2 Ultra) no display controller is wired to the four
rear USB-C ports, so a USB-C DisplayPort display there never lights up.
The dcpext1 routes in t602x-j474-j475.dtsi sit inside the
APPLE_T602X_NON_ULTRA block together with the USB4/PCIe-C wiring, and
t6022 does not define it.

The die-0 half of the t6022 keeps the plain labels and the same rear-port
wiring as the M2 Max Studio. macOS on a J475d drives a DP alt mode display
on rear ports 1 and 2 from DCPEXT1 through the display crossbar (ADT
display-crossbar0, "display-crossbar,t602x"), the same controller the
non-Ultra boards use. Keep only the USB4 aliases, the PCIe-C tunnels and
the non-Ultra display iommus under the guard. The dcpext1 display routes,
dpaudio2, the ATC crossbars and the always-on ATC common power domains now
apply to J475d too.

t6022-jxxxd.dtsi points the display subsystem at the die-1 HDMI DART only,
so add dispext1_dart to it on J475d for the framebuffers of the new pipe.

J474s and J475c keep the same nodes and properties; only the position of
the dcpext1 alias within /aliases changes.

Signed-off-by: Jacob Crowther <3944151+jcrowthe@users.noreply.github.com>
---
 arch/arm64/boot/dts/apple/t6022-j475d.dts      |  9 +++++++++
 arch/arm64/boot/dts/apple/t602x-j474-j475.dtsi | 15 ++++++++++++++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/apple/t6022-j475d.dts b/arch/arm64/boot/dts/apple/t6022-j475d.dts
index 6c09afcffc9a69..35f002d23d6e8d 100644
--- a/arch/arm64/boot/dts/apple/t6022-j475d.dts
+++ b/arch/arm64/boot/dts/apple/t6022-j475d.dts
@@ -45,6 +45,15 @@
 	power-domains = <&ps_dispext0_cpu0_die1>, <&ps_dptx_phy_ps_die1>;
 };
 
+/*
+ * HDMI scans out through dispext0 on die 1, and the rear USB-C ports through
+ * dcpext1/dispext1 on die 0 (see t602x-j474-j475.dtsi).
+ */
+&display {
+	iommus = <&dispext0_dart_die1 0 0x100 0x0 0x10 0x0>,
+		 <&dispext1_dart 0 0x100 0x0 0x10 0x0>;
+};
+
 &dcpext0_die1 {
 	// J180 misses "function-dp2hdmi_pwr_en"
 	dp2hdmi-pwren-gpios = <&smc_gpio 25 GPIO_ACTIVE_HIGH>;
diff --git a/arch/arm64/boot/dts/apple/t602x-j474-j475.dtsi b/arch/arm64/boot/dts/apple/t602x-j474-j475.dtsi
index 822760c80ae598..22827a0ffab38f 100644
--- a/arch/arm64/boot/dts/apple/t602x-j474-j475.dtsi
+++ b/arch/arm64/boot/dts/apple/t602x-j474-j475.dtsi
@@ -24,7 +24,6 @@
 #ifdef APPLE_T602X_NON_ULTRA
 / {
 	aliases {
-		dcpext1 = &dcpext1;
 		/* Same Thunderbolt aliases as the 14/16-inch boards. This mini
 		 * brings up a fourth controller.
 		 */
@@ -67,6 +66,19 @@
 	iommus = <&dispext0_dart 0 0x100 0x0 0x10 0x0>,
 		 <&dispext1_dart 0 0x100 0x0 0x10 0x0>;
 };
+#endif
+
+/*
+ * dcpext1 on die 0 drives the rear USB-C ports through the display crossbar
+ * on all of these boards, M2 Ultra included: macOS routes a DP alt mode
+ * display on the J475d's rear ports to DCPEXT1 as well. Only the USB4 and
+ * PCIe-C wiring below stays non-Ultra.
+ */
+/ {
+	aliases {
+		dcpext1 = &dcpext1;
+	};
+};
 
 &dispext1_dart {
 	status = "okay";
@@ -229,6 +241,7 @@
 	apple,always-on;
 };
 
+#ifdef APPLE_T602X_NON_ULTRA
 &usb4_0_acio {
 	apple,pcie-tunnel = <&usb4_0_pcie_tunnel>;
 };