[metal] Reprogram PIT 0 (system timer) before enabling IRQ 0

libc/irq/acpi-fadt.c

@@ -493,15 +493,23 @@ textstartup void _AcpiFadtInit(void) {
       return;
     }
     length = fadt->Header.Length;
-    ACPI_INFO("FADT @ %p,+%#zx", fadt, length);
+    ACPI_INFO("FADT %.8!s @ %p,+%#zx", fadt->Header.OemTableId, fadt, length);
     _Static_assert(offsetof(AcpiTableFadt, Dsdt) == 40);
     _Static_assert(offsetof(AcpiTableFadt, BootFlags) == 109);
     _Static_assert(offsetof(AcpiTableFadt, XDsdt) == 140);
     if (length >= offsetof(AcpiTableFadt, BootFlags) + sizeof(fadt->BootFlags))
     {
-      _AcpiBootFlags = flags = fadt->BootFlags;
+      flags = fadt->BootFlags;
+      if (READ64LE(fadt->Header.OemTableId) == READ64LE("BXPC    ")) {
+        /* Work around incomplete AML tables under QEMU. */
+        ACPI_WARN("FADT: boot flags %#x -> %#x (QEMU workaround)",
+                  (unsigned)flags, (unsigned)(flags | kAcpiFadtLegacyDevices));
+        flags |= kAcpiFadtLegacyDevices;
+      } else {
         ACPI_INFO("FADT: boot flags %#x", (unsigned)flags);
       }
+      _AcpiBootFlags = flags;
+    }
     if (length >= offsetof(AcpiTableFadt, XDsdt) + sizeof(fadt->XDsdt) &&
         fadt->XDsdt) {
       dsdt_phy = fadt->XDsdt;

libc/irq/acpi-xsdt.c

@@ -193,13 +193,14 @@ textstartup void _AcpiXsdtInit(void) {
       ACPI_INFO("no RSDP found");
       return;
     }
-    ACPI_INFO("RSDP @ %p", rsdp);
+    ACPI_INFO("RSDP OEM %.6!s @ %p", rsdp->OemId, rsdp);
     if (rsdp->Revision <= 1 ||
         rsdp->Length < offsetof(AcpiTableRsdp, Reserved) ||
         !rsdp->XsdtPhysicalAddress) {
       const AcpiTableRsdt *rsdt = _AcpiMapTable(rsdp->RsdtPhysicalAddress);
       nents = (rsdt->Header.Length - sizeof(rsdt->Header)) / sizeof(uint32_t);
-      ACPI_INFO("RSDT @ %p, %#zx entries", rsdt, nents);
+      ACPI_INFO("RSDT %.8!s @ %p, %#zx entries", rsdt->Header.OemTableId, rsdt,
+                                                 nents);
       ents = _AcpiOsAllocate(nents * sizeof(AcpiTableHeader *));
       if (ents) {
         for (i = 0; i < nents; ++i) {
@@ -209,7 +210,8 @@ textstartup void _AcpiXsdtInit(void) {
     } else {
       const AcpiTableXsdt *xsdt = _AcpiMapTable(rsdp->XsdtPhysicalAddress);
       nents = (xsdt->Header.Length - sizeof(xsdt->Header)) / sizeof(uint64_t);
-      ACPI_INFO("XSDT @ %p, %#zx entries", xsdt, nents);
+      ACPI_INFO("XSDT %.8!s @ %p, %#zx entries", xsdt->Header.OemTableId, xsdt,
+                                                 nents);
       ents = _AcpiOsAllocate(nents * sizeof(AcpiTableHeader *));
       if (ents) {
         for (i = 0; i < nents; ++i) {

libc/irq/acpi.internal.h

@@ -348,8 +348,8 @@ _AcpiCompressHid(const uint8_t *__hid, size_t __len) {
   __c = __hid[6];
   if (__c < '0' || __c > 'F' || (__c > '9' && __c < 'A')) return 0;
   __d3 = __c <= '9' ? __c - '0' : __c - 'A' + 0xA;
-  __evalu = (uint32_t)__a0 << 26 | (uint32_t)__a1 << 21 | (uint32_t)__a2 << 16 |
+  __evalu = (uint32_t)__a0 << 26 | (uint32_t)__a1 << 21 | (uint32_t)__a2 << 16
-          __d0 << 12 | __d1 << 8 | __d2 << 4 | __d3;
+            | __d0 << 12 | __d1 << 8 | __d2 << 4 | __d3;
   return bswap_32(__evalu);
 }
 
@@ -382,6 +382,12 @@ forceinline bool _AcpiDecompressHid(uintmax_t __hid,
   return true;
 }
 
+forceinline AcpiDeviceHid _AcpiMakePnpHid(uint16_t __pnp_id) {
+  uint32_t __evalu = (uint32_t)16 << 26 | (uint32_t)14 << 21 |
+                     (uint32_t)16 << 16 | __pnp_id;
+  return bswap_32(__evalu);
+}
+
 #define ACPI_INFO(FMT, ...)                                            \
         do {                                                           \
           if (!IsTiny()) {                                             \

libc/irq/irq-8259.c

@@ -34,7 +34,24 @@
 
 #ifdef __x86_64__
 
-textstartup void _Irq8259Init(void) {
+textstartup static const AcpiDefDevice *_AcpiFindDevice(AcpiDeviceHid hid) {
+  const AcpiDefDevice *dev = _AcpiDefDevices;
+  while (dev && dev->hid != hid) dev = dev->next;
+  return dev;
+}
+
+textstartup static void _Pit0Init(void) {
+  if (!(_AcpiBootFlags & kAcpiFadtLegacyDevices) &&
+      !_AcpiFindDevice(_AcpiMakePnpHid(0x0100))) {
+    ACPI_FATAL("no 8254 PIT");
+  }
+  ACPI_INFO("resetting 8254 PIT");
+  outb(PIT_CMD, PIT_SC0 | PIT_RW | PIT_SQW);
+  outb(PIT0_DATA, 0x00);
+  outb(PIT0_DATA, 0x00);
+}
+
+textstartup static void _Irq8259Init(void) {
   if (_weaken(_ApicDisableAll)) _weaken(_ApicDisableAll)();
   ACPI_INFO("starting 8259 IRQs");
   outb(PIC1_CMD, PIC_INIT | PIC_IC4);  /* ICW1 */
@@ -51,12 +68,14 @@ textstartup void _Irq8259Init(void) {
   /* Send EOIs for good measure. */
   outb(PIC1_CMD, PIC_EOI);
   outb(PIC2_CMD, PIC_EOI);
+  /* Reprogram PIT 0. */
   enable();
 }
 
 textstartup void _IrqHwInit(void) {
   if (!_weaken(_AcpiMadtFlags) ||
       (_AcpiMadtFlags & kAcpiMadtPcAtCompat) != 0) {
+    _Pit0Init();
     _Irq8259Init();
   } else {
     /* TODO */

libc/runtime/pc.internal.h

@@ -147,6 +147,21 @@
 #define PIC_READ_IRR 0x0a /* OCW3 irq ready next CMD read */
 #define PIC_READ_ISR 0x0b /* OCW3 irq service next CMD read */
 
+/*
+ * @see Intel Corporation.  82C54 CHMOS Programmable Interval Timer.  1994.
+ *      Intel order number 23124-006.
+ */
+#define PIT       0x40       /* IO base address for PIT */
+#define PIT0_DATA (PIT + 0)
+#define PIT1_DATA (PIT + 1)
+#define PIT2_DATA (PIT + 2)
+#define PIT_CMD   (PIT + 3)
+#define PIT_SC0   0x00       /* select counter 0 */
+#define PIT_SC1   0x00       /* select counter 1 */
+#define PIT_SC2   0x00       /* select counter 2 */
+#define PIT_RW    0x30       /* read/write operation */
+#define PIT_SQW   0x06       /* square wave mode */
+
 /* Long Mode Paging
    @see Intel Manual V.3A §4.1 §4.5
                                           IsValid (ignored on CR3) V┐