[jcrowthe]

Thunderbolt displays on the Mac Studio (M2 Ultra, J475d). Stacked on #462: the first commit here is #462's. Please review the last three.

1. thunderbolt: apple: qualify the M2 Ultra (t6022) for DP tunnels
2. phy: apple: atc: qualify the M2 Ultra and the fourth die-0 ATC for DP tunnels
3. arm64: dts: apple: t6022-j475d: wire Thunderbolt DP tunnels on the rear ports

Problem

A Thunderbolt display on a J475d rear port enumerates, but the DP tunnel is torn down after the DPRX timeout and the display gets no signal:

thunderbolt 0-1: LG Electronics 40WP95C
thunderbolt-apple-nhi f01f00000.nhi: 0:5 <-> 1:13 (DP): not active, tearing down
thunderbolt-apple-nhi f01f00000.nhi: 0:6 <-> 1:13 (DP): not active, tearing down

5a07508 kept M2 desktops out on purpose ("M2 desktops, T6002 and T8112 remain disabled"), pending hardware qualification. On t6022 three gates are closed:

• apple_dpin_qualified_soc (thunderbolt_apple) has t6020/t6021 but not t6022, so the DP IN adapter never asks for a pipeline.
• apple_atc_t602x_qualified() (phy-apple-atc) has the same list, and apple_atc_t602x_core_valid() only knows the laptop ATC0-2 bases. The desktops' fourth rear port is ATC3 at 0x1303000000.
• The M2 pre/post flow needs dual-stream wiring (apple_dp_tunnel_dual_stream()): two DCPs per connector with typecN-dpin0/1 on crossbar cells 1 and 2. The J474/J475 trees only wire dcpext1 to the rear ports, for DP alt mode (arm64: dts: apple: t6022-j475d: enable DP alt mode on the rear USB-C ports #462).

Changes

1. Add t6022 to apple_dpin_qualified_soc. Its die-0 ACIO, ATC and crossbar are the t6021 blocks, and the DCPs are the same apple,t6020-dcpext.
2. Add t6022 to apple_atc_t602x_qualified() and ATC3 (0x1303000000) to apple_atc_t602x_core_valid().
3. J475d DT. HDMI runs from die 1, so die-0 dcpext0 is free:
   • enable it as a USB-C-only pipeline for the four rear ports, at crossbar state 0 (dcpext1 stays at state 2, as on the laptops);
   • give both die-0 DCPs typecN-dpin0/1 controls on crossbar cells 1 and 2;
   • add the second endpoint to each rear connector's port@3;
   • add dispext0_dart to the display iommus;
   • add the dcpext0 alias.

The KUnit tables for both qualification gates are updated, with a t6022 row for unwired connectors that stays disabled.

m1n1 needs an alias for every enabled DCP

m1n1 sets apple,firmware-compat (and reserves the firmware) only through the ADT-indexed dcpext0…dcpext7 aliases. My first boot with dcpext0 enabled had no dcpext0 alias:

apple-dcp 289c00000.dcp: Could not read 'apple,firmware-compat': -22

and the whole apple-drm aggregate stayed down, HDMI included, so the desktop fell back to 1080p simpledrm. On t6022 the ADT index of die-0 dcpext0 is 0 (dcpext0@89C00000), dcpext1 is 1 and die-1 dcpext0 (HDMI) is 4, which is how the aliases are set. Any future board that enables another DCP needs the matching alias.

KUnit

tools/testing/kunit/kunit.py run --arch=arm64 (QEMU, -cpu max, 16K pages, clang 18.1.8) with USB4_APPLE_DPIN_KUNIT_TEST, PHY_APPLE_ATC_KUNIT_TEST and DRM_APPLE_FABRIC_KUNIT_TEST:

Tree	Result
This branch	182 tests: 181 passed, 1 skipped (S35_dual_retry_off, skipped by the suite itself)
Updated tests on the old code	3 failed: atc_tunnel_soc_qualification, atc_tunnel_core_qualification, apple_dpin_qualification_profiles
bed544b + #462	181 passed, 1 skipped

Device tree check

Built with the kernel's own scripts/dtc:

• t6020-j474s and t6021-j475c have the same sorted contents as the dtbs in linux-aurora 7.2.11.aurora16-1.
• For t6022-j475d, each rear connector (usb-pd@38, @3f, @3b, @3c) has two bidirectional endpoints, to dcpext1 and dcpext0. Both DCPs carry typecN / typecN-dpin0 / typecN-dpin1 on cells 0/1/2 of the same atcN-dpxbar, which is what apple_dp_tunnel_route_wired() checks.

Hardware testing

Mac Studio (M2 Ultra, 2023), apple,j475d / apple,t6022. The base is linux-aurora 7.2.11.aurora16-1 (bed544b). thunderbolt_apple.ko and phy-apple-atc.ko were rebuilt from this branch (clang 18.1.8, same vermagic) into updates/ with the initramfs regenerated, and the J475d dtb was built from this branch. OS firmware 13.5, system firmware 26.6.2. m1n1 stage 2 is ba130ffb + omacom/m1n1#46 + the T602x DART patch from #379, which the HDMI DCP needs on this machine (#428). Hyprland 0.57.2.

Displays: LG 40WP95C (5120x2160) over Thunderbolt; LG UltraFine 4K over a USB-C to DisplayPort cable; Dell U2718Q on HDMI.

All three DCPs bind and boot:

apple-drm soc@200000000:display-subsystem: bound 289c00000.dcp (ops dcp_comp_ops [appledrm])
apple-drm soc@200000000:display-subsystem: bound 315c00000.dcp (ops dcp_comp_ops [appledrm])
apple-drm soc@200000000:display-subsystem: bound 2289c00000.dcp (ops dcp_comp_ops [appledrm])
apple-dcp 289c00000.dcp: DCP booted
apple-dcp 315c00000.dcp: DCP booted
apple-dcp 2289c00000.dcp: DCP booted

Thunderbolt on rear port 2:

apple-dcp 315c00000.dcp: display routed to Thunderbolt DP tunnel dpin0
thunderbolt-apple-acio f01ac0000.cio: dpin0: active handshake=0
thunderbolt-apple-nhi f01f00000.nhi: 0:5 <-> 1:13 (DP): Apple: DP tunnel paths up, not waiting for DPRX
apple-display-crossbar f0304c000.mux: Switched dpin0 to dispext1,0
apple-dcp 315c00000.dcp: set_digital_out_mode(color:71 timing:60) "5120x2160": 72 ...
apple-dcp 315c00000.dcp: set_digital_out_mode() color mode depth:10 ...

Results (rear ports counted from the left, looking at the back):

Action	Result
Thunderbolt coldplug, rear 2 (f01ac0000.cio)	pass, 5120x2160@72, 10 bpc
Thunderbolt unplug/replug, rear 2	pass: dpin0: inactive, crossbar link down, dcp_dptx_disconnect; back at 5120x2160@72 about 2.4 s after new device found
Thunderbolt on rear 1 (1301ac0000.cio, ATC3 / phy@1303000000)	pass, 5120x2160@72
DPMS off/on with the tunnel up, 5 cycles	pass, dpin0: inactive / crossbar link down on off, active / crossbar link up and modeset on on
Thunderbolt + DP alt mode (rear 4, dcpext0) + HDMI (dcpext4) at once	pass, 5120x2160@72 + 3840x2160@60 + 3840x2160@60
DP alt mode on rear 1–4 (from #462)	pass
Front USB-C ports (die 1)	not tested, not wired
Second stream on one port (dpin1), MST, dual-stream docks	not tested, no such dock here
DP audio over the tunnel	not tested
Suspend/resume	not tested
PCIe over Thunderbolt	not working, out of scope. An ORARA U2E-01 enumerates, then PCIe-C is not initialized by m1n1 or the kernel. apple_pcie_tunnel_cold_init_machines in the built-in pcie-apple also lacks t6022.

No WARNING, BUG or oops in any boot. Messages seen that do not stop the display:

• thunderbolt-apple-nhi ...: device links to tunneled native ports are missing! (also present before these changes, see j475d (Mac Studio M2 Ultra): dcpext RTKit boot times out (-62), apple-drm never binds — HDMI and Thunderbolt displays all stuck on simpledrm #428)
• tps6598x 0-003b: cable revalidation failed after 3 attempts
• phy-apple-atc ...: Failed to lock pipehandler once per port during a move. This also appears with the stock modules during DP alt mode hotplug.

The repeated screen wake while locked is the Dell dropping HPD in standby combined with aquamarine, hyprwm/aquamarine#495. The tunnel goes down and comes back up cleanly through each of those cycles.

Not covered

The J474s and J475c use die-0 dcpext0 for HDMI, so their dual-stream wiring needs a different layout. With the ATC3 fix here, they could probably follow the 14/16-inch pattern (dcpext0 for HDMI plus Type-C routes), but I can't test that.