drm/asahi: dispatch G15 compute through extended T8122 firmware

drivers/gpu/drm/asahi/file.rs

@@ -1350,9 +1350,15 @@ impl File {
             cls_pr_debug!(Errors, "queue_create: Invalid priority\n");
             return Err(EINVAL);
         }
-        // HIGH has only been run on G17; G13 and G14 keep refusing it.
+        // Keep support tied to a backend and admitted profile. G13/G14 and
+        // unqualified M3 profiles retain their previous rejection.
+        let high_supported = reg_data.gpu.as_any().is::<crate::g17::Gpu>();
+        #[cfg(CONFIG_DRM_ASAHI_M3_T8122)]
+        let high_supported = high_supported || reg_data.gpu.as_any()
+            .downcast_ref::<crate::m3::m3_drm::Backend>()
+            .is_some_and(|gpu| gpu.supports_high_priority());
         if data.priority == uapi::drm_asahi_priority_DRM_ASAHI_PRIORITY_HIGH
-            && !reg_data.gpu.as_any().is::<crate::g17::Gpu>()
+            && !high_supported
         {
             cls_pr_debug!(
                 Errors,

drivers/gpu/drm/asahi/m3/m3_board.rs

@@ -13,7 +13,7 @@ use crate::m3::m3_resources::{
 use crate::m3::m3_soc::Soc;
 
 /// Whether the root node's compatible list contains `compatible`.
-fn board_is(compatible: &[u8]) -> bool {
+pub(crate) fn board_is(compatible: &[u8]) -> bool {
     let Some(root) = kernel::of::root() else {
         return false;
     };

drivers/gpu/drm/asahi/m3/m3_completion.rs

@@ -24,10 +24,9 @@ impl WorkItem for Completion {
     type Pointer = Arc<Self>;
     fn run(owner: Arc<Self>) {
         use crate::m3::m3_runtime::Service;
-        // Snapshots after a notification before sleeping for the next one: the completion
-        // stamps can trail the firmware's event message.
-        const TRAILING_POLLS: u32 = 4;
-        let (mut trailing, mut waited_at) = (0, u64::MAX);
+        // No deliberate spin: fsleep(5) selects udelay, not a scheduler sleep.
+        // Check immediately on IRQ, with backoff for trailing coherent witnesses.
+        let mut policy = super::m3_completion_policy::WaitPolicy::new();
         loop {
             let (outcome, events) = {
                 let mut guard = owner.shared.lock();
@@ -37,23 +36,20 @@ impl WorkItem for Completion {
                 // Preserve the root-only CPU-overlap diagnostic: disabled waits retain
                 // the runtime lock so VM/timestamp preparation cannot overlap the GPU.
                 if let Service::Waiting(messages)=outcome {
-                    if !events.cpu_overlap() {events.wait_past(messages);continue;}
+                    if !events.cpu_overlap() {
+                        events.wait_past(messages, policy.next_wait_us(events.wait_ceiling_us()));
+                        continue;
+                    }
                 }
                 (outcome,events)
             };
             match outcome {
                 Service::Idle => break,
-                Service::Progress => { trailing = 0; waited_at = u64::MAX; }
+                Service::Progress => policy.progress(),
                 Service::Waiting(messages) => {
-                    if messages != waited_at { waited_at = messages; trailing = 0; }
-                    if trailing < TRAILING_POLLS {
-                        trailing += 1;
-                        kernel::time::delay::fsleep(kernel::time::Delta::from_micros(5));
-                    } else {
-                        // Until the next firmware event, or a bounded 100 us resnapshot.
-                        events.wait_past(messages);
-                        trailing = 0;
-                    }
+                    // IRQs and timer expiry alone are not retirement progress.
+                    // Keep backing off until service publishes or retires work.
+                    events.wait_past(messages, policy.next_wait_us(events.wait_ceiling_us()));
                 }
             }
         }

drivers/gpu/drm/asahi/m3/m3_completion_policy.rs

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+
+//! Bounded fallback for witnesses which can become visible after the last IRQ.
+//!
+//! Notifications request a fresh snapshot, but do not prove witness progress.
+//! Only publication or retirement resets this policy. In particular, neither a
+//! timer wake nor a stream of early firmware notifications renews a spin budget.
+
+pub(crate) struct WaitPolicy {
+    next_us: u64,
+}
+
+impl WaitPolicy {
+    pub(crate) const fn new() -> Self {
+        Self { next_us: 25 }
+    }
+
+    pub(crate) fn progress(&mut self) {
+        self.next_us = 25;
+    }
+
+    /// No deliberate busy delay: IRQs still wake each sleep immediately.
+    /// The caller supplies the root-selected ceiling (25..=1000 us).
+    pub(crate) fn next_wait_us(&mut self, ceiling_us: u64) -> u64 {
+        let wait = self.next_us.min(ceiling_us.clamp(25, 1000));
+        self.next_us = (wait * 2).min(1000);
+        wait
+    }
+}
+
+#[cfg_attr(not(test), kernel::macros::kunit_tests(asahi_m3_completion_policy))]
+mod tests {
+    use super::WaitPolicy;
+
+    #[test]
+    fn no_progress_backs_off_and_stays_bounded() {
+        let mut policy = WaitPolicy::new();
+        for expected in [25, 50, 100, 200, 400, 800, 1000, 1000] {
+            assert_eq!(policy.next_wait_us(1000), expected);
+        }
+        for _ in 0..100_000 {
+            assert_eq!(policy.next_wait_us(1000), 1000);
+        }
+    }
+
+    #[test]
+    fn publication_or_retirement_restarts_fast_detection() {
+        let mut policy = WaitPolicy::new();
+        for _ in 0..8 { policy.next_wait_us(1000); }
+        policy.progress();
+        assert_eq!(policy.next_wait_us(1000), 25);
+        assert_eq!(policy.next_wait_us(1000), 50);
+    }
+
+    #[test]
+    fn live_ceiling_changes_apply_to_the_next_wait() {
+        let mut policy = WaitPolicy::new();
+        for _ in 0..8 { policy.next_wait_us(1000); }
+        assert_eq!(policy.next_wait_us(25), 25);
+        assert_eq!(policy.next_wait_us(1000), 50);
+        assert_eq!(policy.next_wait_us(100), 100);
+        assert_eq!(policy.next_wait_us(100), 100);
+    }
+
+    #[test]
+    fn fallback_keeps_timeout_checks_frequent_without_any_irq() {
+        let mut policy = WaitPolicy::new();
+        let mut elapsed_us = 0;
+        while elapsed_us < 2_000_000 {
+            let wait = policy.next_wait_us(1000);
+            assert!(wait <= 1000);
+            elapsed_us += wait;
+        }
+        // This bounds the requested delay, not scheduler dispatch latency.
+        assert!(elapsed_us < 2_001_000);
+    }
+}