drm/asahi: default J516C display on and defer GPU until ready

arch/arm64/boot/dts/apple/t6031-dcp.dtsi

@@ -9,9 +9,10 @@
  * interrupts and DART windows are those of the J516C ADT.
  *
  * Every node stays status = "disabled". The display gate enables the DCP,
- * its mailbox, the two DARTs and the display subsystem only when
- * apple_t6031_display.enable=1 is on the kernel command line and the boot
- * loader has set apple,t6031-handoff = <1>. Compatibles are t6031-specific,
+ * its mailbox, the two DARTs and the display subsystem only when the boot
+ * loader has set apple,t6031-handoff = <1> and the native display is
+ * requested: by default on the J516C, with apple_t6031_display.enable=1 on
+ * the other boards, never with apple_t6031_display.enable=0. Compatibles are t6031-specific,
  * so a kernel that does not know them leaves the nodes unbound.
  *
  * Only the T6031 board files include this file: t6034.dtsi includes

drivers/gpu/drm/apple/apple_drv.c

@@ -57,28 +57,44 @@ struct apple_drm_private {
 };
 
 /* Component readiness is later than platform probe/bind. */
-static DEFINE_MUTEX(apple_t6030_display_lock);
+static DEFINE_MUTEX(apple_g15_display_lock);
 static struct device *apple_t6030_display;
+static struct device *apple_t6031_display;
 
-static int apple_t6030_display_publish(struct device *dev)
+/* The publication slot of a G15 SoC's internal display subsystem, or NULL. */
+static struct device **apple_g15_display_slot(struct device *dev)
 {
-	if (!of_device_is_compatible(dev->of_node, "apple,t6030-display-subsystem"))
+	if (of_device_is_compatible(dev->of_node, "apple,t6030-display-subsystem"))
+		return &apple_t6030_display;
+	if (of_device_is_compatible(dev->of_node, "apple,t6031-display-subsystem"))
+		return &apple_t6031_display;
+	return NULL;
+}
+
+static int apple_g15_display_publish(struct device *dev)
+{
+	struct device **slot = apple_g15_display_slot(dev);
+
+	if (!slot)
 		return 0;
-	guard(mutex)(&apple_t6030_display_lock);
-	if (apple_t6030_display)
-		return apple_t6030_display == dev ? 0 : -EBUSY;
-	apple_t6030_display = get_device(dev);
+	guard(mutex)(&apple_g15_display_lock);
+	if (*slot)
+		return *slot == dev ? 0 : -EBUSY;
+	*slot = get_device(dev);
 	return 0;
 }
 
-static void apple_t6030_display_withdraw(struct device *dev)
+static void apple_g15_display_withdraw(struct device *dev)
 {
+	struct device **slot = apple_g15_display_slot(dev);
 	struct device *old = NULL;
 
-	scoped_guard(mutex, &apple_t6030_display_lock) {
-		if (apple_t6030_display == dev) {
-			old = apple_t6030_display;
-			apple_t6030_display = NULL;
+	if (!slot)
+		return;
+	scoped_guard(mutex, &apple_g15_display_lock) {
+		if (*slot == dev) {
+			old = *slot;
+			*slot = NULL;
 		}
 	}
 	put_device(old);
@@ -89,22 +105,35 @@ static void apple_t6030_display_withdraw(struct device *dev)
  * publish separately. This lock protects only publication and a device link;
  * no display calls or firmware RPC run while it is held.
  */
-int apple_drm_t6030_link_device(struct device *consumer)
+static int apple_g15_link_device(struct device *consumer, const char *machine,
+				 const char *gpu, struct device **display)
 {
 	struct device_link *link;
 
-	if (!of_machine_is_compatible("apple,t6030") || !consumer->of_node ||
-	    !of_device_is_compatible(consumer->of_node, "apple,agx-t6030"))
+	if (!of_machine_is_compatible(machine) || !consumer->of_node ||
+	    !of_device_is_compatible(consumer->of_node, gpu))
 		return -ENODEV;
-	guard(mutex)(&apple_t6030_display_lock);
-	if (!apple_t6030_display)
+	guard(mutex)(&apple_g15_display_lock);
+	if (!*display)
 		return -EPROBE_DEFER;
-	link = device_link_add(consumer, apple_t6030_display,
-			       DL_FLAG_AUTOREMOVE_CONSUMER);
+	link = device_link_add(consumer, *display, DL_FLAG_AUTOREMOVE_CONSUMER);
 	return link ? 0 : -EINVAL;
 }
+
+int apple_drm_t6030_link_device(struct device *consumer)
+{
+	return apple_g15_link_device(consumer, "apple,t6030", "apple,agx-t6030",
+				     &apple_t6030_display);
+}
 EXPORT_SYMBOL_GPL(apple_drm_t6030_link_device);
 
+int apple_drm_t6031_link_device(struct device *consumer)
+{
+	return apple_g15_link_device(consumer, "apple,t6031", "apple,agx-t6031",
+				     &apple_t6031_display);
+}
+EXPORT_SYMBOL_GPL(apple_drm_t6031_link_device);
+
 DEFINE_DRM_GEM_DMA_FOPS(apple_fops);
 
 #define DART_PAGE_SIZE 16384
@@ -1089,7 +1118,7 @@ static int apple_drm_init(struct device *dev)
 	drm_client_setup_with_fourcc(&apple->drm, DRM_FORMAT_XRGB8888);
 
 	/* A subsequent successful platform probe retries deferred GPU probes. */
-	ret = apple_t6030_display_publish(dev);
+	ret = apple_g15_display_publish(dev);
 	if (ret) {
 		drm_dev_unregister(&apple->drm);
 		goto err_unbind;
@@ -1111,7 +1140,7 @@ static void apple_drm_uninit(struct device *dev)
 {
 	struct apple_drm_private *apple = dev_get_drvdata(dev);
 
-	apple_t6030_display_withdraw(dev);
+	apple_g15_display_withdraw(dev);
 
 	apple_drm_quiesce_connectors(&apple->drm);
 	drm_dev_unplug(&apple->drm);

drivers/gpu/drm/asahi/g15/boot.rs

@@ -1,3 +1,3 @@
 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 
 //! Admission and firmware start to READY.
@@ -72,6 +72,7 @@
         fn asahi_g15_ioremap_wc(start: u64, size: usize) -> *mut core::ffi::c_void;
         fn asahi_g15_dma_coherent(dev: *mut core::ffi::c_void) -> bool;
         pub(crate) fn asahi_g15_pmp_prepare(dev: *mut core::ffi::c_void) -> core::ffi::c_int;
+        pub(crate) fn asahi_g15_display_prepare(dev: *mut core::ffi::c_void) -> core::ffi::c_int;
         pub(crate) fn asahi_g15_pmp_get(dev: *mut core::ffi::c_void) -> core::ffi::c_int;
         pub(crate) fn asahi_g15_pmp_put(dev: *mut core::ffi::c_void);
         fn asahi_g15_reserved_uat(index: u32, start: u64, size: u64) -> bool;
@@ -482,6 +483,17 @@
     } else if !glue::machine(cfg.machine) {
         dev_err!(dev, "G15: not a {} machine\n", cfg.name);
         return Err(ENODEV);
+    } else {
+        // No PMP vote here, but the first start follows the native display all the same.
+        // SAFETY: `dev` is the bound GPU device.
+        let ret = unsafe { glue::asahi_g15_display_prepare(dev.as_raw().cast()) };
+        if ret != 0 {
+            let err = Error::from_errno(ret);
+            if err != EPROBE_DEFER {
+                dev_err!(dev, "native display not admitted: {:?}\n", err);
+            }
+            return Err(err);
+        }
     }
     let adt = adt::read(dev, cfg)
         .inspect_err(|e| dev_err!(dev, "GPU regions not admitted: {:?}\n", e))?;

drivers/gpu/drm/asahi/g15/glue.c

@@ -34,6 +34,7 @@ int asahi_g15_adt_phram(u64 *start, u64 *size);
 void __iomem *asahi_g15_ioremap_wc(u64 start, size_t size);
 bool asahi_g15_dma_coherent(struct device *dev);
 int asahi_g15_pmp_prepare(struct device *dev);
+int asahi_g15_display_prepare(struct device *dev);
 int asahi_g15_pmp_get(struct device *dev);
 void asahi_g15_pmp_put(struct device *dev);
 bool asahi_g15_reserved_uat(u32 index, u64 start, u64 size);
@@ -141,6 +142,33 @@ int asahi_g15_pmp_prepare(struct device *dev)
 	return apple_pmp_link_device(dev);
 }
 
+/*
+ * T6031 has no PMP vote, but its first firmware start follows the native
+ * display as T6030's does: defer until that display is up. The display can
+ * be off for this boot (no handoff, or not requested), so say once why. An
+ * enabled display that is not published yet is said once too: if it never
+ * comes up (its DCP refused or failed to bind), that line is why the GPU
+ * stays off.
+ */
+int asahi_g15_display_prepare(struct device *dev)
+{
+	struct device_node *np;
+	int ret;
+
+	if (!dev->of_node || !of_device_is_compatible(dev->of_node, "apple,agx-t6031"))
+		return -ENODEV;
+	ret = apple_drm_t6031_link_device(dev);
+	if (ret != -EPROBE_DEFER)
+		return ret;
+	np = of_find_compatible_node(NULL, NULL, "apple,t6031-display-subsystem");
+	if (!np || !of_device_is_available(np))
+		dev_info_once(dev, "G15: waiting for the T6031 native display, which this boot did not enable (it needs the boot loader's display handoff, and apple_t6031_display.enable=1 except on the J516C)\n");
+	else
+		dev_info_once(dev, "G15: waiting for the T6031 native display to come up: the GPU firmware starts only after the display is published\n");
+	of_node_put(np);
+	return ret;
+}
+
 int asahi_g15_pmp_get(struct device *dev)
 {
 	if (!asahi_g15_board() || !dev->of_node ||

drivers/gpu/drm/asahi/g15/mod.rs

@@ -1,3 +1,3 @@
 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 
 //! G15 GPU support (T6030, M3 Pro: J514S, J516S; firmware RTKit 2419, the macOS 14.7-14.8 stub).
@@ -14,9 +14,9 @@
 //!
 //! # Plugging into the shared driver
 //!
-//! - [`Driver`] is a separate platform driver. T6030 has a module alias; its probe must wait
-//!   for the native display and PMP supplier before booting firmware. T6031 retains explicit
-//!   module loading. It calls [`crate::driver::AsahiPlatformDriver::probe_g15`].
+//! - [`Driver`] is a separate platform driver with a module alias. Its probe must wait for
+//!   the native display (T6030 and T6031) and the PMP supplier (T6030) before booting
+//!   firmware. It calls [`crate::driver::AsahiPlatformDriver::probe_g15`].
 //! - [`Gpu`] implements [`crate::gpu::Gpu`]: GET_PARAMS identity, VM creation (`new_vm`),
 //!   queues (`new_queue`, see [`queue`]) and timestamp buffers.
 //! - User VMs are shared-layer [`mmu::Vm`]s on a [`mmu::Uat::new_adopted`] UAT with tracked
@@ -152,14 +152,16 @@
         ),
     ]);
 
-// T6030 probe admission requires the native display and PMP supplier before
-// firmware starts. T6031 retains explicit loading until it has an equivalent
-// display-order admission gate.
+// Probe admission requires the native display before firmware starts (T6030
+// also its PMP supplier), so both may be loaded at device creation.
 kernel::of_device_table!(
     AUTOLOAD_OF_TABLE,
     MODULE_OF_TABLE_G15,
     (),
-    [(of::DeviceId::new(c_str!("apple,agx-t6030")), ())]
+    [
+        (of::DeviceId::new(c_str!("apple,agx-t6030")), ()),
+        (of::DeviceId::new(c_str!("apple,agx-t6031")), ()),
+    ]
 );
 
 /// The G15 platform adapter: the shared DRM registration probed through

drivers/soc/apple/Kconfig

@@ -228,9 +228,14 @@ config APPLE_T6030_DISPLAY_GATE
 	  nomodeset.
 
 	  It also serves T6031 (M3 Max) device trees with apple,t6031-handoff,
-	  in the same way, but only for a boot with
-	  apple_t6031_display.enable=1 on the kernel command line, and only
-	  with the PMP values the boot loader passes.
+	  in the same way and only with the PMP values the boot loader passes.
+	  There the native display is on by default on the J516C, unless
+	  apple_t6031_display.enable=0; the other T6031 boards need
+	  apple_t6031_display.enable=1 on the kernel command line. The T6031
+	  GPU driver starts its firmware only after this native display is
+	  up, so apple_t6031_display.enable=0, or a native display that does
+	  not come up, also keeps the GPU off for that boot. It is not a
+	  display-only switch.
 
 	  Say 'y' if you want the native display on M3 Pro MacBook Pros.
 
@@ -258,10 +263,11 @@ config APPLE_DISPLAY_GATE_KUNIT_TEST
 	default KUNIT_ALL_TESTS
 	help
 	  Runs the display gate on test device trees with the T6030, T6031
-	  and T8122 display nodes, without Apple hardware. On T6031: off by
-	  default, enabled only by apple_t6031_display.enable=1, only with the
-	  boot loader's handoff marker and this Mac's PMP values, and with
-	  nothing changed when a check fails. On T6030: on by default, as
+	  and T8122 display nodes, without Apple hardware. On T6031: on by
+	  default only on the default board (the J516C), otherwise only with
+	  apple_t6031_display.enable=1, off with apple_t6031_display.enable=0,
+	  only with the boot loader's handoff marker and this Mac's PMP values,
+	  and with nothing changed when a check fails. On T6030: on by default, as
 	  before, whatever the T6031 option says. On T8122: on by default,
 	  and nothing changed when the handoff or the device tree's own PMP
 	  topology does not check out.