feat: add support for aarch64 timer/interrupts, port MontaukOS userspace

kernel/src/Drivers/USB/Xhci.cpp

@@ -220,6 +220,13 @@ namespace Drivers::USB::Xhci {
         *(volatile uint32_t*)(g_opBase + reg) = value;
     }
 
+    // PollEvents() acknowledges the Port Status Change event, clearing PRC,
+    // so a controller that resets instantly (QEMU) can complete the reset
+    // between two reads of PRC. A port that left reset enabled is done too.
+    static bool PortResetComplete(uint32_t portsc) {
+        return (portsc & PORTSC_PRC) || ((portsc & PORTSC_PED) && !(portsc & PORTSC_PR));
+    }
+
     static uint32_t ReadOp(uint32_t reg) {
         return *(volatile uint32_t*)(g_opBase + reg);
     }
@@ -474,6 +481,16 @@ namespace Drivers::USB::Xhci {
         BudgetExhausted,
     };
 
+    // Without MSI nothing interrupts: the deferred-work check (timer and
+    // idle loop) looks at the event ring itself instead. This is the only
+    // mode on platforms whose PCIe has no MSI controller (Raspberry Pi 4).
+    static bool g_pollMode = false;
+
+    static bool EventRingHasWork() {
+        const volatile TRB& evt = g_evtRing[g_evtRingDequeue];
+        return ((evt.Control & TRB_CYCLE_BIT) != 0) == g_evtRingCCS;
+    }
+
     static PollResult PollEventsBounded(uint32_t maxEvents) {
         // PollEvents runs from synchronous poll loops (ControlTransfer,
         // SendCommand, firmware download) and idle bottom halves on different
@@ -1396,6 +1413,9 @@ namespace Drivers::USB::Xhci {
     }
 
     bool HasDeferredWork() {
+        if (g_initialized && g_pollMode && EventRingHasWork()) {
+            g_irqDrainPending.store(true, std::memory_order_release);
+        }
         return g_initialized &&
             (g_irqDrainPending.load(std::memory_order_acquire) ||
              g_deferredWorkPending.load(std::memory_order_acquire) ||
@@ -1537,7 +1557,7 @@ namespace Drivers::USB::Xhci {
                     for (uint32_t i = 0; i < 100000; i++) {
                         PollEvents();
                         uint32_t ps = ReadOp(OP_PORTSC_BASE + port * OP_PORTSC_STRIDE);
-                        if (ps & PORTSC_PRC) {
+                        if (PortResetComplete(ps)) {
                             resetDone = true;
                             break;
                         }
@@ -1732,6 +1752,7 @@ namespace Drivers::USB::Xhci {
         // MSI setup
         if (!SetupMsi(dev.Bus, dev.Device, dev.Function)) {
             KernelLogStream(WARNING, "xHCI") << "MSI not available, using poll mode";
+            g_pollMode = true;
         }
 
         // Enable interrupter 0
@@ -1772,7 +1793,7 @@ namespace Drivers::USB::Xhci {
             for (uint32_t i = 0; i < 100000; i++) {
                 PollEvents();
                 uint32_t ps = ReadOp(OP_PORTSC_BASE + port * OP_PORTSC_STRIDE);
-                if (ps & PORTSC_PRC) { resetDone = true; break; }
+                if (PortResetComplete(ps)) { resetDone = true; break; }
                 for (int j = 0; j < 100; j++) Arch::CompilerBarrier();
             }
 
@@ -2045,6 +2066,7 @@ namespace Drivers::USB::Xhci {
         // -----------------------------------------------------------------
         if (!SetupMsi(foundDev->Bus, foundDev->Device, foundDev->Function)) {
             KernelLogStream(WARNING, "xHCI") << "MSI not available, using poll mode";
+            g_pollMode = true;
         }
 
         // -----------------------------------------------------------------