drm/asahi: prepare native defaults for supported M3 Air and Pro

arch/arm64/configs/asahi.config

@@ -45,6 +45,8 @@ CONFIG_VIDEO_APPLE_AVD=m
 CONFIG_VIDEO_APPLE_ISP=m
 CONFIG_DRM=y
 CONFIG_DRM_ASAHI=m
+CONFIG_DRM_ASAHI_M3_T8122=y
+CONFIG_DRM_ASAHI_G15=y
 CONFIG_DRM_ADP=m
 CONFIG_DRM_APPLE=m
 CONFIG_DRM_APPLE_AUDIO=y

drivers/gpu/drm/asahi/Kconfig

@@ -56,10 +56,11 @@ config DRM_ASAHI_M3_T8122
 	help
 	  Build the M3 runtime that starts the GPU of the M3 MacBook Air
 	  (J613, J615) on the 14.8.3 GPU firmware the boot loader leaves
-	  loaded. It starts only with asahi.t8122_start=1 on the kernel
-	  command line, after the boot loader handed the GPU over; without
-	  it the T8122 probe is refused as before. Other GPUs are not
-	  affected.
+	  loaded. On the listed Air boards it starts after the boot loader
+	  handed the GPU over and resource/firmware identity checks pass.
+	  asahi.t8122_start=0 keeps startup disabled for recovery. Unknown
+	  boards and firmware do not gain automatic admission. Other GPUs
+	  are not affected.
 
 config DRM_ASAHI_G15
 	bool "Native G15 firmware backend (M3 Pro/Max)"

drivers/gpu/drm/asahi/m3/m3_soc.rs

@@ -1,3 +1,3 @@
 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 
 //! The per-SoC facts of the M3 runtime backend.
@@ -272,10 +272,9 @@
 /// the one the T8122 identity gate admits (`t8122_admission`: family 7, variant 2, revision 0x20,
 /// core slots in the first core-mask word only), with the die count of the AGX3 identification
 /// table (`hw::agx3::T8122`). The hardware configuration is `hw::t8122`; power configuration
-/// comes from the boot loader. The rest of the runtime configuration is complete, but until the
-/// runtime has passed on an M3 MacBook Air the SoC is refused, before the GPU is accessed, unless
-/// `asahi.t8122_start=1` arms the start (`t8122_start`), which uses this table's values and adds a
-/// performance-state cap.
+/// comes from the boot loader. Startup uses the guarded `t8122_start` path, which selects this
+/// table's values by default on admitted Air boards and adds a performance-state cap. Explicit
+/// `asahi.t8122_start=0` disables startup; firmware, board and resource admission still apply.
 pub(crate) static T8122: Soc = Soc {
     name: "T8122",
     gpu_name: "G15G",
@@ -326,7 +325,7 @@
     },
     power_from_boot_loader: true,
     unported: &[
-        "a pass on an M3 MacBook Air: until then the GPU starts only with asahi.t8122_start=1",
+        "M3 Air startup requires the guarded t8122_start path and its performance-state cap",
     ],
     // The performance state only. On the single-cluster G15G, reading the engine-busy or the
     // fault-bank registers after every job hangs the SoC within seconds at about 1000 jobs/s;

drivers/gpu/drm/asahi/m3/t8122_knobs.rs

@@ -1,3 +1,3 @@
 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 
 //! The parameters of the T8122 start experiment (`t8122_start`): their text, defaults, accepted
@@ -132,6 +132,17 @@
     }
 }
 
+/// The shipped board policy changes only an omitted start parameter. Explicit recovery-off,
+/// explicit experimental start, and malformed values retain their original meanings.
+/// Hardware resources and firmware identity are admitted separately by the caller.
+pub(crate) fn start_for_board(raw: &Raw, admitted_board: bool) -> Start {
+    if raw.start == UNSET && admitted_board {
+        Start::On
+    } else {
+        start(raw)
+    }
+}
+
 /// The GPU clock-generator IO mapping.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub(crate) enum ClockGen {
@@ -232,6 +243,19 @@
         assert!(with(|r| r.fender = INVALID).values_given());
     }
 
+    #[test]
+    fn automatic_start_is_board_scoped_and_explicit_values_win() {
+        assert_eq!(start_for_board(&Raw::NONE, true), Start::On);
+        assert_eq!(start_for_board(&Raw::NONE, false), Start::Off);
+        for admitted_board in [false, true] {
+            assert_eq!(start_for_board(&with(|r| r.start = 0), admitted_board), Start::Off);
+            assert_eq!(start_for_board(&with(|_| {}), admitted_board), Start::On);
+            assert_eq!(start_for_board(&with(|r| r.start = 2), admitted_board), Start::Invalid);
+            assert_eq!(start_for_board(&with(|r| r.start = INVALID), admitted_board), Start::Invalid);
+            assert_eq!(start_for_board(&with(|r| r.start = parse_number("bogus")), admitted_board), Start::Invalid);
+        }
+    }
+
     #[test]
     fn defaults_are_the_plan_baseline() {
         let v = resolve(&with(|_| {})).unwrap();

drivers/gpu/drm/asahi/m3/t8122_start.rs

@@ -1,11 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0-only OR MIT
 
-//! The T8122 (M3, G15G) start, `asahi.t8122_start=1`.
+//! T8122 (M3, G15G) board-default startup and bounded experiment values.
 //!
-//! The T8122 table (`m3_soc::T8122`) is complete, but the runtime has not passed on an M3
-//! MacBook Air yet, so the SoC is refused unless `asahi.t8122_start=1` arms the start. On a T8122
-//! whose GPU the boot loader handed over (resource admission passed), an armed start uses the
-//! table's values, with a performance-state cap. Each value can be overridden for a lab A/B by
+//! The T8122 table (`m3_soc::T8122`) is complete. An omitted start parameter starts
+//! automatically only on its listed Air boards; explicit `asahi.t8122_start=0`
+//! remains the recovery opt-out. Resource and known-firmware admission still run.
+//! The same table values can be changed for a controlled experiment by
 //! rebooting with a parameter:
 //!
 //! | Parameter | Default | Others |
@@ -19,7 +19,7 @@
 //! | `asahi.t8122_pstate_cap` | `2` | 1 to 5 |
 //!
 //! The defaults are the T8122 table's values. A parameter given with a value it does not accept
-//! refuses the start. Without `asahi.t8122_start=1` nothing here runs, and T8122 is refused.
+//! refuses the start. Unlisted boards remain refused by the existing backend admission.
 //! Nothing here applies to any other SoC.
 
 use core::mem::offset_of;
@@ -237,22 +237,22 @@
 
 /// Decide, after resource admission, whether `soc` starts with the experiment values.
 ///
-/// Any SoC but T8122: Ok(None), silently. T8122 without `asahi.t8122_start=1`: Ok(None), so the
-/// caller refuses it as before (one extra line when experiment parameters were given). T8122
-/// with `asahi.t8122_start=1`: the experiment, after logging every value, or a refusal for a
-/// parameter value it does not accept.
+/// Any SoC but T8122: Ok(None). On its listed Air boards, an omitted parameter
+/// selects the table values; explicit 0 disables startup, and invalid values fail
+/// closed. Existing backend admission still refuses an unlisted board, even
+/// with an explicit start request.
 pub(crate) fn arm(dev: &device::Device, soc: &Soc) -> Result<Option<Experiment>> {
     if !is_t8122(soc) {
         return Ok(None);
     }
     let raw = crate::m3::m3_params::t8122_params();
-    match knobs::start(&raw) {
+    match knobs::start_for_board(&raw, crate::m3::m3_board::runtime_validated_board(soc)) {
         Start::On => {}
         Start::Off => {
             if raw.values_given() {
                 dev_info!(
                     dev,
-                    "M3 G15G start: asahi.t8122_* values given without asahi.t8122_start=1; ignored\n"
+                    "M3 G15G start: disabled by asahi.t8122_start=0; other asahi.t8122_* values ignored\n"
                 );
             }
             return Ok(None);
@@ -283,7 +283,7 @@
     let e = Experiment(v);
     dev_warn!(
         dev,
-        "M3 G15G start: armed (asahi.t8122_start=1, boot loader handoff admitted): initdata_version={:#018x} fender={:#x} clkgen={} sgx_setup={} unit_mask_a={:#x} unit_mask_b={:#x} pstate_cap={}\n",
+        "M3 G15G start: armed (board default or asahi.t8122_start=1, boot loader handoff admitted): initdata_version={:#018x} fender={:#x} clkgen={} sgx_setup={} unit_mask_a={:#x} unit_mask_b={:#x} pstate_cap={}\n",
         v.initdata_version,
         v.fender,
         clkgen_label(v.clock_gen, v.fender),
@@ -352,9 +352,12 @@
     }
 }
 
-/// Log, on a T8122 armed with `asahi.t8122_start=1`, that resource admission refused it.
+/// Log that resource admission refused a T8122 start selected by board default or flag.
 pub(crate) fn not_admitted(dev: &device::Device, soc: &Soc) {
-    if is_t8122(soc) && knobs::start(&crate::m3::m3_params::t8122_params()) == Start::On {
+    if is_t8122(soc) && knobs::start_for_board(
+        &crate::m3::m3_params::t8122_params(),
+        crate::m3::m3_board::runtime_validated_board(soc),
+    ) == Start::On {
         dev_err!(
             dev,
             "M3 G15G start: not armed: resource admission refused the GPU (see the lines above); the boot loader did not hand it over completely\n"