SchOS/kernel/acpi/aml.c

// SPDX-License-Identifier: GPL-2.0-or-later
//
// What the kernel uses AML for. See include/acpi.h.
//
// Interrupt routing is the reason this exists. A PCI device's config space
// names an interrupt line, but that number is the 8259's: the firmware
// programmed it for an OS running the legacy PICs, and with the I/O APIC in
// use the device is on some other pin entirely. Which pin is written down
// only in the namespace, as each PCI root bridge's _PRT -- a table from
// (device, INTx pin) to either a GSI or a "link device" whose _CRS holds the
// GSI. Without reading it, every INTx device on a real board waited on the
// wrong pin, and only MSI and the poller (kernel/dev/irq.c) kept anything
// working at all.
//
// The rest is what every machine expects of an OS once it has ACPI: the
// power button powers it off cleanly, and power-off and reset go through the
// firmware's own registers rather than an emulator's magic ports.

#include "types.h"
#include "defs.h"
#include "param.h"
#include "x86.h"
#include "spinlock.h"
#include "pci.h"
#include "irq.h"
#include "acpi.h"

#include <uacpi/uacpi.h>
#include <uacpi/utilities.h>
#include <uacpi/namespace.h>
#include <uacpi/resources.h>
#include <uacpi/event.h>
#include <uacpi/sleep.h>

static int ready;

static uacpi_interrupt_ret power_button(uacpi_handle ctx);

void
acpi_aml_init(void)
{
  uacpi_status st;

  if (acpi_rsdp_phys() == 0)
    return;

  st = uacpi_initialize(0);
  if (uacpi_unlikely_error(st)) {
    cprintf("acpi: tables not usable: %s\n", uacpi_status_to_string(st));
    return;
  }
  st = uacpi_namespace_load();
  if (uacpi_unlikely_error(st)) {
    cprintf("acpi: AML would not load: %s\n", uacpi_status_to_string(st));
    return;
  }

  // \_PIC(1): tell the firmware the I/O APIC is in use, so that _PRT answers
  // with I/O APIC inputs rather than PIC lines. Before _INI runs, which on
  // some boards reads the answer.
  uacpi_set_interrupt_model(UACPI_INTERRUPT_MODEL_IOAPIC);

  st = uacpi_namespace_initialize();
  if (uacpi_unlikely_error(st)) {
    cprintf("acpi: namespace would not initialize: %s\n",
            uacpi_status_to_string(st));
    return;
  }

  st = uacpi_install_fixed_event_handler(UACPI_FIXED_EVENT_POWER_BUTTON,
                                         power_button, 0);
  if (uacpi_unlikely_error(st) && st != UACPI_STATUS_COMPILED_OUT)
    kinfo("acpi: no fixed power button: %s\n", uacpi_status_to_string(st));

  uacpi_finalize_gpe_initialization();
  ready = 1;
  kinfo("acpi: namespace loaded\n");
}

// --- power -------------------------------------------------------------------

// Run in the worker thread, not the SCI handler: syncing the filesystems
// sleeps, and S5 runs AML.
static void
power_off_work(uacpi_handle ctx)
{
  (void)ctx;
  cprintf("acpi: power button pressed; syncing and powering off\n");
  schfs_ksync_all();
  acpi_poweroff();
  cprintf("acpi: power-off failed; it is safe to switch off now\n");
}

static uacpi_interrupt_ret
power_button(uacpi_handle ctx)
{
  static int once;
  (void)ctx;
  if (!once) {
    once = 1;
    uacpi_kernel_schedule_work(UACPI_WORK_NOTIFICATION, power_off_work, 0);
  }
  return UACPI_INTERRUPT_HANDLED;
}

int
acpi_poweroff(void)
{
  if (!ready)
    return -1;
  if (uacpi_unlikely_error(uacpi_prepare_for_sleep_state(UACPI_SLEEP_STATE_S5)))
    return -1;
  cli();
  uacpi_enter_sleep_state(UACPI_SLEEP_STATE_S5);
  sti();
  return -1;
}

int
acpi_reboot(void)
{
  if (!ready)
    return -1;
  uacpi_reboot();
  return -1;
}

// --- PCI interrupt routing ---------------------------------------------------

#define MAXBUS 256

// The bridge leading to each secondary bus, from the devices pci_init found.
static struct pci_dev *upstream[MAXBUS];

static uacpi_namespace_node *root_bridge;

static uacpi_iteration_decision
found_root(void *user, uacpi_namespace_node *node, uacpi_u32 depth)
{
  uacpi_u64 bbn = 0;
  (void)user;
  (void)depth;
  // _BBN is the bridge's first bus. Absent means 0, and bus 0 is the one
  // whose devices are all that most machines have.
  uacpi_eval_simple_integer(node, "_BBN", &bbn);
  if (bbn == 0 && root_bridge == 0) {
    root_bridge = node;
    return UACPI_ITERATION_DECISION_BREAK;
  }
  return UACPI_ITERATION_DECISION_CONTINUE;
}

// The namespace node of the device at (slot, func) below `parent`: the child
// whose _ADR says so.
static uacpi_namespace_node *
child_at(uacpi_namespace_node *parent, int slot, int func)
{
  uacpi_namespace_node *child = 0;
  uacpi_u64 adr;

  while (uacpi_namespace_node_next(parent, &child) == UACPI_STATUS_OK) {
    if (uacpi_eval_simple_integer(child, "_ADR", &adr) == UACPI_STATUS_OK &&
        adr == (((uacpi_u64)slot << 16) | (uacpi_u64)func))
      return child;
  }
  return 0;
}

struct irqfind {
  uint32 index;
  int    gsi;
  int    mode;
};

static int
mode_of(int triggering, int polarity)
{
  int level = triggering == UACPI_TRIGGERING_LEVEL;
  int low = polarity == UACPI_POLARITY_ACTIVE_LOW;
  return level ? (low ? IRQ_LEVEL_LOW : IRQ_LEVEL_HIGH)
               : (low ? IRQ_EDGE_LOW : IRQ_EDGE_HIGH);
}

static uacpi_iteration_decision
link_irq(void *user, uacpi_resource *r)
{
  struct irqfind *f = user;

  if (r->type == UACPI_RESOURCE_TYPE_IRQ && r->irq.num_irqs > 0) {
    f->gsi = r->irq.irqs[f->index < r->irq.num_irqs ? f->index : 0];
    f->mode = mode_of(r->irq.triggering, r->irq.polarity);
    return UACPI_ITERATION_DECISION_BREAK;
  }
  if (r->type == UACPI_RESOURCE_TYPE_EXTENDED_IRQ &&
      r->extended_irq.num_irqs > 0) {
    f->gsi = r->extended_irq.irqs[f->index < r->extended_irq.num_irqs
                                  ? f->index : 0];
    f->mode = mode_of(r->extended_irq.triggering, r->extended_irq.polarity);
    return UACPI_ITERATION_DECISION_BREAK;
  }
  return UACPI_ITERATION_DECISION_CONTINUE;
}

// Look (slot, pin) up in a _PRT. Returns the GSI, or -1. A link device's
// current setting is used as it stands: firmware programs every link at
// boot, and one it left disabled is reported rather than reconfigured.
static int
prt_lookup(uacpi_pci_routing_table *t, int slot, int pin, int *mode)
{
  for (uacpi_size i = 0; i < t->num_entries; i++) {
    uacpi_pci_routing_table_entry *e = &t->entries[i];
    if ((e->address >> 16) != (uint32)slot || e->pin != pin)
      continue;

    if (e->source == 0) {
      *mode = IRQ_LEVEL_LOW;           // a bare GSI is PCI's signalling
      return e->index;
    }

    uacpi_resources *res;
    struct irqfind f = { e->index, -1, IRQ_LEVEL_LOW };
    if (uacpi_get_current_resources(e->source, &res) != UACPI_STATUS_OK)
      return -1;
    uacpi_for_each_resource(res, link_irq, &f);
    uacpi_free_resources(res);
    if (f.gsi <= 0) {
      uacpi_object_name nm = uacpi_namespace_node_name(e->source);
      char name[5] = { nm.text[0], nm.text[1], nm.text[2], nm.text[3], 0 };
      cprintf("acpi: link %s for slot %d is disabled\n", name, slot);
      return -1;
    }
    *mode = f.mode;
    return f.gsi;
  }
  return -1;
}

static int
route_one(struct pci_dev *d, uacpi_pci_routing_table *roottab, int *mode)
{
  // The chain of bridges from bus 0 down to this device's bus.
  struct pci_dev *chain[8];
  int n = 0, bus = d->bus;
  while (bus != 0 && n < 8 && upstream[bus]) {
    chain[n++] = upstream[bus];
    bus = upstream[bus]->bus;
  }
  if (bus != 0)
    return -1;                         // a bus not reached from bus 0

  // Walk down the namespace alongside it, as far as the namespace describes
  // the bridges. The deepest bridge with its own _PRT is where the lookup
  // happens; below it, INTx pins are swizzled by the PCI-to-PCI bridge rule.
  uacpi_namespace_node *node = root_bridge;
  uacpi_pci_routing_table *tab = roottab, *owned = 0;
  int at = n;                          // chain[at..] lies below tab's bus
  for (int i = n - 1; i >= 0 && node; i--) {
    node = child_at(node, chain[i]->slot, chain[i]->func);
    uacpi_pci_routing_table *t;
    if (node && uacpi_get_pci_routing_table(node, &t) == UACPI_STATUS_OK) {
      if (owned)
        uacpi_free_pci_routing_table(owned);
      tab = owned = t;
      at = i;
    }
  }

  int pin = pci_read8(d->bus, d->slot, d->func, 0x3D) - 1;   // 0 = INTA
  int slot = d->slot;
  for (int i = 0; i < at; i++) {
    pin = (pin + slot) % 4;
    slot = chain[i]->slot;
  }
  // The device is now (slot, pin) on the bus `tab` describes: that bridge's
  // secondary bus, or bus 0 for the root table.

  int gsi = prt_lookup(tab, slot, pin, mode);
  if (owned)
    uacpi_free_pci_routing_table(owned);
  return gsi;
}

void
acpi_pci_route(void)
{
  uacpi_pci_routing_table *roottab;
  int i, routed = 0, beyond = 0;

  if (!ready)
    return;
  uacpi_find_devices("PNP0A08", found_root, 0);    // PCI Express
  if (!root_bridge)
    uacpi_find_devices("PNP0A03", found_root, 0);  // conventional PCI
  if (!root_bridge ||
      uacpi_get_pci_routing_table(root_bridge, &roottab) != UACPI_STATUS_OK) {
    kinfo("acpi: no _PRT on the root bridge; PCI lines left as found\n");
    return;
  }

  for (i = 0; i < pci_count(); i++) {
    struct pci_dev *d = pci_get(i);
    if ((d->header_type & 0x7F) == 1) {
      int sec = pci_read8(d->bus, d->slot, d->func, 0x19);
      if (sec > 0 && sec < MAXBUS)
        upstream[sec] = d;
    }
  }

  for (i = 0; i < pci_count(); i++) {
    struct pci_dev *d = pci_get(i);
    int mode, gsi;

    if (pci_read8(d->bus, d->slot, d->func, 0x3D) == 0)
      continue;                        // uses no INTx pin at all
    gsi = route_one(d, roottab, &mode);
    if (gsi < 0)
      continue;
    if (gsi >= NIRQ_IOAPIC) {
      // A second I/O APIC's input. Not reachable here; MSI still is. AMD
      // boards wire every PCIe bridge's devices to the GNB's I/O APIC, so
      // on those this is most of the machine.
      d->irq = 0xFF;
      beyond++;
      continue;
    }
    if (gsi != d->irq)
      kinfo("acpi: %d:%d.%d INT%c is gsi %d, not %d\n", d->bus, d->slot,
            d->func, 'A' + pci_read8(d->bus, d->slot, d->func, 0x3D) - 1,
            gsi, d->irq);
    d->irq = gsi;
    d->irq_mode = mode;
    routed++;
  }
  uacpi_free_pci_routing_table(roottab);
  kinfo("acpi: %d PCI interrupt%s routed through _PRT\n", routed,
        routed == 1 ? "" : "s");
  if (beyond)
    kinfo("acpi: %d more on a second I/O APIC, which is not driven; "
          "those devices need MSI\n", beyond);
}