dev/acpica/acpi_spmc.c

/*
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2024-2026 The FreeBSD Foundation
 *
 * This software was developed by Aymeric Wibo <obiwac@freebsd.org>
 * under sponsorship from the FreeBSD Foundation.
 *
 * Portions of this software were developed by Olivier Certner
 * <olce@FreeBSD.org> at Kumacom SARL under sponsorship from the FreeBSD
 * Foundation.
 */

#include <sys/param.h>
#include <sys/bus.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/uuid.h>

#include <machine/_inttypes.h>

#include <contrib/dev/acpica/include/acpi.h>
#include <contrib/dev/acpica/include/accommon.h>

#include <dev/acpica/acpivar.h>


/* Hooks for the ACPI CA debugging infrastructure */
#define _COMPONENT	ACPI_SPMC
ACPI_MODULE_NAME("SPMC")

static char *spmc_ids[] = {
	"PNP0D80",
	NULL
};

/* sysctl(8) knobs */
static SYSCTL_NODE(_debug_acpi, OID_AUTO, spmc, CTLFLAG_RD | CTLFLAG_MPSAFE,
    NULL, "SPMC debugging");

int8_t dsm_intel_revision = -15;
SYSCTL_S8(_debug_acpi_spmc, OID_AUTO, intel_dsm_revision, CTLFLAG_RW,
    &dsm_intel_revision, 0,
    "Revision to use with the Intel DSM "
    "(negative: auto, try from 0 to minus the value)");

int8_t dsm_amd_revision = -15;
SYSCTL_S8(_debug_acpi_spmc, OID_AUTO, amd_dsm_revision, CTLFLAG_RW,
    &dsm_amd_revision, 0,
    "Revision to use with the AMD DSM "
    "(negative: auto, try from 0 to minus the value)");

int8_t dsm_ms_revision = -15;
SYSCTL_S8(_debug_acpi_spmc, OID_AUTO, ms_dsm_revision, CTLFLAG_RW,
    &dsm_ms_revision, 0,
    "Revision to use with the Microsoft DSM "
    "(negative: auto, try from 0 to minus the value)");

static int verbose;
SYSCTL_INT(_debug_acpi_spmc, OID_AUTO, verbose, CTLFLAG_RW,
    &verbose, 0, "acpi_spmc(4) verbosity");

#define VERBOSE()	(verbose || bootverbose)

static bool force_call_expected_functions;
SYSCTL_BOOL(_debug_acpi_spmc, OID_AUTO, always_call_expected_functions,
    CTLFLAG_RW, &force_call_expected_functions, 0,
    "Call all expected functions on a present DSM, even those not enumerated.");

/* Conversion of an index to a mask. */
#define IDX_TO_BIT(idx)		(1ull << (idx))

/* List of supported DSMs. */
#define DSM_INTEL			0
#define DSM_MS				1
#define DSM_AMD				2

/* List of DSM function indices. */
#define DSM_ENUM_FUNCTIONS		0	/* Common to all DSMs */
#define DSM_GET_DEVICE_CONSTRAINTS	1	/* AMD and Intel, MS N/A */

#define DSM_GET_CRASH_DUMP_DEVICE	2	/* Intel, MS N/A */
#define DSM_INTEL_MS_DISPLAY_OFF_NOTIF	3
#define DSM_INTEL_MS_DISPLAY_ON_NOTIF	4
#define DSM_INTEL_MS_LPI_ENTRY_NOTIF	5
#define DSM_INTEL_MS_LPI_EXIT_NOTIF	6

#define DSM_MS_SLEEP_ENTRY_NOTIF	7
#define DSM_MS_SLEEP_EXIT_NOTIF		8
#define DSM_MS_TURN_ON_DISPLAY		9

#define DSM_AMD_LPI_ENTRY_NOTIF		2
#define DSM_AMD_LPI_EXIT_NOTIF		3
#define DSM_AMD_DISPLAY_OFF_NOTIF	4
#define DSM_AMD_DISPLAY_ON_NOTIF	5


/* Descriptors for the DSMs we support. */

struct dsm_desc {
	const char		*name;
	struct uuid		 uuid;
	/*
	 * Points to an integer which, if negative, indicates to auto-detect the
	 * revision by trying all revisions between 0 and minus the value, else
	 * is the sole revision to try.
	 */
	const int8_t		*revision_spec;
	uint64_t		 expected_functions;
	uint64_t		 extra_functions;
	/* Human-friendly names of known functions. */
	const char *const	*function_names;
	int			 function_names_nb;
	/* Index in the dsms[] array below. */
	int			 index;
};

static const char *const dsm_intel_function_names[] = {
	[DSM_GET_DEVICE_CONSTRAINTS] = "DEVICE_CONSTRAINTS",
	[DSM_GET_CRASH_DUMP_DEVICE] = "CRASH_DUMP_DEVICE",
	[DSM_INTEL_MS_DISPLAY_OFF_NOTIF] = "DISPLAY_OFF",
	[DSM_INTEL_MS_DISPLAY_ON_NOTIF] = "DISPLAY_ON",
	[DSM_INTEL_MS_LPI_ENTRY_NOTIF] = "LPI_ENTRY",
	[DSM_INTEL_MS_LPI_EXIT_NOTIF] = "LPI_EXIT",
};

static const struct dsm_desc dsm_intel = {
	.index = DSM_INTEL,
	.name = "Intel",
	.uuid = { /* c4eb40a0-6cd2-11e2-bcfd-0800200c9a66 */
		0xc4eb40a0, 0x6cd2, 0x11e2, 0xbc, 0xfd,
		{0x08, 0x00, 0x20, 0x0c, 0x9a, 0x66}
	},
	.revision_spec = &dsm_intel_revision,
	.expected_functions =
	    IDX_TO_BIT(DSM_GET_DEVICE_CONSTRAINTS) |
	    IDX_TO_BIT(DSM_INTEL_MS_DISPLAY_OFF_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_DISPLAY_ON_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_LPI_ENTRY_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_LPI_EXIT_NOTIF),
	.extra_functions =
	    IDX_TO_BIT(DSM_GET_CRASH_DUMP_DEVICE), /* Not used. */
	.function_names = dsm_intel_function_names,
	.function_names_nb = nitems(dsm_intel_function_names),
};

static const char *const dsm_ms_function_names[] = {
	[DSM_INTEL_MS_DISPLAY_OFF_NOTIF] = "DISPLAY_OFF",
	[DSM_INTEL_MS_DISPLAY_ON_NOTIF] = "DISPLAY_ON",
	[DSM_INTEL_MS_LPI_ENTRY_NOTIF] = "LPI_ENTRY",
	[DSM_INTEL_MS_LPI_EXIT_NOTIF] = "LPI_EXIT",
	[DSM_MS_SLEEP_ENTRY_NOTIF] = "SLEEP_ENTRY",
	[DSM_MS_SLEEP_EXIT_NOTIF] = "SLEEP_EXIT",
	[DSM_MS_TURN_ON_DISPLAY] = "TURN_ON",
};

static const struct dsm_desc dsm_ms = {
	.index = DSM_MS,
	.name = "Microsoft",
	.uuid = { /* 11e00d56-ce64-47ce-837b-1f898f9aa461 */
		0x11e00d56, 0xce64, 0x47ce, 0x83, 0x7b,
		{0x1f, 0x89, 0x8f, 0x9a, 0xa4, 0x61}
	},
	.revision_spec = &dsm_ms_revision,
	.expected_functions =
	    IDX_TO_BIT(DSM_INTEL_MS_DISPLAY_OFF_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_DISPLAY_ON_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_LPI_ENTRY_NOTIF) |
	    IDX_TO_BIT(DSM_INTEL_MS_LPI_EXIT_NOTIF) |
	    IDX_TO_BIT(DSM_MS_SLEEP_ENTRY_NOTIF) |
	    IDX_TO_BIT(DSM_MS_SLEEP_EXIT_NOTIF),
	.extra_functions =
	    IDX_TO_BIT(DSM_MS_TURN_ON_DISPLAY),
	.function_names = dsm_ms_function_names,
	.function_names_nb = nitems(dsm_ms_function_names),
};

static const char *const dsm_amd_function_names[] = {
	[DSM_GET_DEVICE_CONSTRAINTS] = "DEVICE_CONSTRAINTS",
	[DSM_AMD_DISPLAY_OFF_NOTIF] = "DISPLAY_OFF",
	[DSM_AMD_DISPLAY_ON_NOTIF] = "DISPLAY_ON",
	[DSM_AMD_LPI_ENTRY_NOTIF] = "LPI_ENTRY",
	[DSM_AMD_LPI_EXIT_NOTIF] = "LPI_EXIT",
};

static const struct dsm_desc dsm_amd = {
	.index = DSM_AMD,
	.name = "AMD",
	.uuid = { /* e3f32452-febc-43ce-9039-932122d37721 */
		0xe3f32452, 0xfebc, 0x43ce, 0x90, 0x39,
		{0x93, 0x21, 0x22, 0xd3, 0x77, 0x21}
	},
	.revision_spec = &dsm_amd_revision,
	.expected_functions =
	    IDX_TO_BIT(DSM_GET_DEVICE_CONSTRAINTS) |
	    IDX_TO_BIT(DSM_AMD_DISPLAY_OFF_NOTIF) |
	    IDX_TO_BIT(DSM_AMD_DISPLAY_ON_NOTIF) |
	    IDX_TO_BIT(DSM_AMD_LPI_ENTRY_NOTIF) |
	    IDX_TO_BIT(DSM_AMD_LPI_EXIT_NOTIF),
	.function_names = dsm_amd_function_names,
	.function_names_nb = nitems(dsm_amd_function_names),
};

static const struct dsm_desc *const dsms[] = {
	[DSM_INTEL] = &dsm_intel,
	[DSM_MS] = &dsm_ms,
	[DSM_AMD] = &dsm_amd,
};

/* Per DSM probed information. */
struct dsm_info {
	uint64_t	supported_functions;
	/*
	 * Revisions are zero or a positive number.  Strictly speaking, next
	 * field should be a 'uint64_t' as per the ACPI spec, but our ACPI DSM
	 * interface takes an 'int' and anyway actual revision numbers never
	 * even exceed the limits of a 'uint8_t'.
	 */
	uint8_t		revision;
};

struct acpi_spmc_constraint {
	bool		enabled;
	char		*name;
	int		min_d_state;
	ACPI_HANDLE	handle;

	/* Intel only.  Currently filled but unused. */
	uint64_t	lpi_uid;
	uint64_t	min_dev_specific_state;

	/* AMD only.  Currently filled but unused. */
	uint64_t	function_states;
};

struct acpi_spmc_softc {
	device_t		dev;
	ACPI_HANDLE		handle;
	struct dsm_info		dsms_info[nitems(dsms)];

	struct eventhandler_entry	*eh_suspend;
	struct eventhandler_entry	*eh_resume;

#ifdef INVARIANTS
	bool				get_constraints_succeeded;
#endif
	size_t				constraint_count;
	struct acpi_spmc_constraint	*constraints;
};


static const struct dsm_desc *
resolve_dsm(int dsm_index)
{
	MPASS(0 <= dsm_index && dsm_index < nitems(dsms));
	return (dsms[dsm_index]);
}

static struct dsm_info *
get_dsm_info(struct acpi_spmc_softc *const sc, const int dsm_index)
{
	MPASS(0 <= dsm_index && dsm_index < nitems(dsms));
	return (&sc->dsms_info[dsm_index]);
}

static const struct dsm_info *
get_const_dsm_info(const struct acpi_spmc_softc *const sc, const int dsm_index)
{
	MPASS(0 <= dsm_index && dsm_index < nitems(dsms));
	return (&sc->dsms_info[dsm_index]);
}

static const uint64_t
get_supported_functions(const struct acpi_spmc_softc *const sc,
    const int dsm_index)
{
	return (get_const_dsm_info(sc, dsm_index)->supported_functions);
}

static const uint8_t
get_revision(const struct acpi_spmc_softc *const sc, const int dsm_index)
{
	return (get_const_dsm_info(sc, dsm_index)->revision);
}

static bool
supports_function_bitset(const uint64_t supported_functions,
    const int function_index)
{
	return ((supported_functions & IDX_TO_BIT(function_index)) != 0);
}

static bool
supports_function(const struct acpi_spmc_softc *const sc, const int dsm_index,
    const int function_index)
{
	return (supports_function_bitset(get_supported_functions(sc, dsm_index),
	    function_index));
}

static bool
has_dsm_bitset(const uint64_t supported_functions)
{
	/* DSM is supported if bit DSM_ENUM_FUNCTIONS (0) is set. */
	return (supports_function_bitset(supported_functions,
	    DSM_ENUM_FUNCTIONS));
}

static bool
has_dsm(const struct acpi_spmc_softc *const sc, const int dsm_index)
{
	return (has_dsm_bitset(get_supported_functions(sc, dsm_index)));
}

typedef const char *pbf_get_name_t(const int, const void *const);

static const char *
pbf_dsm_name(const int dsm_index, const void *const opaque __unused)
{
	return (resolve_dsm(dsm_index)->name);
}

static const char *
dsm_function_name(const struct dsm_desc *const dsm, const int function_index)
{
	MPASS(function_index >= 0);
	if (function_index >= dsm->function_names_nb)
		return (NULL);
	/* May be NULL. */
	return (dsm->function_names[function_index]);
}

static const char *
pbf_function_name(const int function_index, const void *const opaque)
{
	return (dsm_function_name(opaque, function_index));
}

static int
print_bit_field(char *const buf, const size_t buf_size,
    const uint64_t bit_field, const char *const fallback_prefix,
    pbf_get_name_t get_name, const void *const opaque)
{
	uint64_t bf = bit_field;
	char *const buf_end = buf + buf_size;
	char *p = buf;
	int ret = 0;
	bool one_set = false;

#define PBF_PRINT(...)							\
	do {								\
		const __ptrdiff_t rem = MAX(buf_end - p, 0);		\
		const int lret = snprintf(p, rem, __VA_ARGS__);		\
									\
		MPASS(lret >= 0);					\
		p += MIN(lret, rem);					\
		ret += lret;						\
	} while (0)

	if (bf == 0) {
		PBF_PRINT("");
		return (ret);
	}

	do {
		const int b_idx = ffsll(bf) - 1;
		const char *const name = get_name(b_idx, opaque);

		PBF_PRINT(one_set ? "," : "<");
		one_set = true;
		if (name != NULL)
			PBF_PRINT("%s", name);
		else
			PBF_PRINT("%s_%d", fallback_prefix, b_idx);

		bf &= ~IDX_TO_BIT(b_idx);
	} while (bf != 0);
	PBF_PRINT(">");
#undef PBF_PRINT

	return (ret);
}

static void
failed_to_call_dsm(const struct acpi_spmc_softc *const sc,
    const struct dsm_desc *const dsm, const int function_index)
{
	(void)device_printf(sc->dev,
	    "Failed to call DSM %s (rev %u) function %s\n",
	    dsm->name, get_revision(sc, dsm->index),
	    dsm_function_name(dsm, function_index));
}

static void	acpi_spmc_probe_dsm(struct acpi_spmc_softc *const sc,
		    const struct dsm_desc *const dsm);
static void	acpi_spmc_dsm_print(
		    const struct acpi_spmc_softc *const sc,
		    const struct dsm_desc *const dsm);
static int	acpi_spmc_get_constraints(struct acpi_spmc_softc *const sc);
static void	acpi_spmc_free_constraints(struct acpi_spmc_softc *const sc);

static void	acpi_spmc_suspend(device_t dev, enum power_stype stype);
static void	acpi_spmc_resume(device_t dev, enum power_stype stype);

static int
acpi_spmc_probe(device_t dev)
{
	char *name;

	/* Check that this is an enabled device. */
	if (acpi_get_type(dev) != ACPI_TYPE_DEVICE || acpi_disabled("spmc"))
		return (ENXIO);

	if (ACPI_ID_PROBE(device_get_parent(dev), dev, spmc_ids, &name) > 0)
		return (ENXIO);

	device_set_desc(dev, "System Power Management Controller");

	return (BUS_PROBE_DEFAULT);
}

static int
acpi_spmc_attach(device_t dev)
{
	struct acpi_spmc_softc *const sc = device_get_softc(dev);
	const ACPI_HANDLE handle = acpi_get_handle(dev);
	int supported_dsms;
	char buf[32];
	int error;

	/*
	 * ACPI_ID_PROBE() in acpi_spmc_probe() cannot succeed without a handle.
	 */
	MPASS(handle != NULL);

	sc->dev = dev;
	sc->handle = handle;

	supported_dsms = 0;
	for (int i = 0; i < nitems(dsms); ++i) {
		KASSERT(dsms[i] != NULL, ("%s: Sparse dsms[]!", __func__));
		KASSERT(dsms[i]->index == i,
		    ("%s: Inconsistent indices for DSM %s", __func__,
		    dsms[i]->name));

		acpi_spmc_probe_dsm(sc, dsms[i]);
		if (has_dsm(sc, i))
			supported_dsms |= IDX_TO_BIT(i);
	}

	if (supported_dsms == 0) {
		device_printf(dev, "No DSM supported!");
		return (ENXIO);
	}

	print_bit_field(buf, sizeof(buf), supported_dsms, "DSM",
	    pbf_dsm_name, NULL);
	device_printf(dev, "DSMs supported: %s\n", buf);

	/* Print supported functions of usable DSMs. */
	for (int i = 0; i < nitems(dsms); ++i)
		if (has_dsm(sc, i))
			acpi_spmc_dsm_print(sc, dsms[i]);

	/* Get device constraints. We can only call this once so do this now. */
	error = acpi_spmc_get_constraints(sc);
	if (error != 0)
		/* acpi_spmc_get_constraints() takes care of cleaning up. */
		device_printf(dev,
		    "Could not parse power state constraints (%d), "
		    "will not check for them before suspend\n", error);

	sc->eh_suspend = EVENTHANDLER_REGISTER(acpi_post_dev_suspend,
	    acpi_spmc_suspend, dev, EVENTHANDLER_PRI_ANY);
	sc->eh_resume = EVENTHANDLER_REGISTER(acpi_pre_dev_resume,
	    acpi_spmc_resume, dev, EVENTHANDLER_PRI_ANY);

	return (0);
}

static int
acpi_spmc_detach(device_t dev)
{
	struct acpi_spmc_softc *sc = device_get_softc(dev);

	EVENTHANDLER_DEREGISTER(acpi_post_dev_suspend, sc->eh_suspend);
	EVENTHANDLER_DEREGISTER(acpi_pre_dev_resume, sc->eh_resume);
	acpi_spmc_free_constraints(sc);
	return (0);
}

static uint64_t
dsm_missing_functions(const struct dsm_desc *const dsm,
    uint64_t supported_functions)
{
	return (dsm->expected_functions & ~supported_functions);
}

static void
acpi_spmc_dsm_print(const struct acpi_spmc_softc *const sc,
    const struct dsm_desc *const dsm)
{
	/*
	 * Remove the enumeration function bit, which we do not care about when
	 * printing which functions are supported and which we do not want to
	 * report as unknown.
	 */
	const uint64_t supported_functions = ~IDX_TO_BIT(DSM_ENUM_FUNCTIONS) &
	    get_supported_functions(sc, dsm->index);
	const uint64_t missing = dsm_missing_functions(dsm, supported_functions);
	const uint64_t unknown = supported_functions &
	    ~(dsm->expected_functions | dsm->extra_functions);
	char buf[128];

	print_bit_field(buf, sizeof(buf), supported_functions,
	    "FUNC", pbf_function_name, dsm);
	device_printf(sc->dev,
	    "DSM %s, revision %d: Supported functions: %#" PRIx64 "%s\n",
	    dsm->name, get_revision(sc, dsm->index), supported_functions, buf);

	if (VERBOSE() && missing != 0) {
		print_bit_field(buf, sizeof(buf), missing, "FUNC",
		    pbf_function_name, dsm);
		device_printf(sc->dev, "DSM %s: Does not enumerate expected "
		    "functions %#" PRIx64 "%s.  Will skip calling them.\n",
		    dsm->name, missing, buf);
	}

	if (VERBOSE() && unknown != 0) {
		print_bit_field(buf, sizeof(buf), unknown, "FUNC",
		    pbf_function_name, dsm);
		device_printf(sc->dev, "DSM %s: Supports more functions than "
		    "used (%#" PRIx64 "%s), driver might need an upgrade.\n",
		    dsm->name, unknown, buf);
	}
}

/* Returns whether the DSM is supported (enumeration succeeds). */
static bool
probe_dsm_revision(const struct acpi_spmc_softc *const sc,
    const struct dsm_desc *const dsm, const uint8_t revision,
    uint64_t *const supported_functions)
{
	*supported_functions = acpi_DSMQuery(sc->handle,
	    (const uint8_t *)&dsm->uuid, revision);
	return (has_dsm_bitset(*supported_functions));
}

static void
set_dsm_revision(struct acpi_spmc_softc *const sc,
    const struct dsm_desc *const dsm, const uint8_t revision,
    uint64_t supported_functions)
{
	struct dsm_info *const dsm_info = get_dsm_info(sc, dsm->index);

	MPASS(has_dsm_bitset(supported_functions));
	dsm_info->supported_functions = supported_functions;
	dsm_info->revision = revision;
}

static void
acpi_spmc_probe_dsm(struct acpi_spmc_softc *const sc,
    const struct dsm_desc *const dsm)
{
	const int8_t revision_spec = *dsm->revision_spec;
	uint64_t supported_functions;

	if (revision_spec >= 0) {
		/* Specific revision specified. */
		if (probe_dsm_revision(sc, dsm, revision_spec,
		    &supported_functions))
			set_dsm_revision(sc, dsm, revision_spec,
			    supported_functions);
		return;
	}

	/*
	 * Auto-detect.  We try revisions in ascending order, selecting the
	 * first that has all the functions we expect in the hope to avoid potential
	 * backwards-compatibility problems, else continuing with higher ones
	 * but adopting them only if they actually add new functions (it seems
	 * common that firmwares do not care about the revision, or will return
	 * the same supported functions after a revision limit).
	 */
	for (uint8_t revision = 0; revision <= -revision_spec; ++revision) {
		if (!probe_dsm_revision(sc, dsm, revision,
		    &supported_functions))
			continue;
		if ((~get_supported_functions(sc, dsm->index) &
		    supported_functions) == 0)
			/* This revision adds no new function, skip it. */
			continue;

		set_dsm_revision(sc, dsm, revision, supported_functions);

		if (dsm_missing_functions(dsm, ~IDX_TO_BIT(DSM_ENUM_FUNCTIONS) &
		    supported_functions) == 0)
			/* We have all expected functions, bail out. */
			break;
	}
}

static void
acpi_spmc_free_constraints(struct acpi_spmc_softc *const sc)
{
	for (size_t i = 0; i < sc->constraint_count; i++)
		free(sc->constraints[i].name, M_TEMP);
	sc->constraint_count = 0;

	free(sc->constraints, M_TEMP);
	sc->constraints = NULL;
}

static int
acpi_spmc_parse_constraints_intel(struct acpi_spmc_softc *sc, ACPI_OBJECT *object)
{
	struct acpi_spmc_constraint *constraint;
	int		revision;
	ACPI_OBJECT	*constraint_obj;
	ACPI_OBJECT	*name_obj;
	ACPI_OBJECT	*detail;
	ACPI_OBJECT	*constraint_package;

	sc->constraint_count = object->Package.Count;
	sc->constraints = malloc(sc->constraint_count * sizeof *sc->constraints,
	    M_TEMP, M_WAITOK | M_ZERO);

	/*
	 * The value of sc->constraint_count can change during the loop, so
	 * iterate until object->Package.Count so we actually go over all
	 * elements in the package.
	 */
	for (size_t i = 0, j = 0; i < object->Package.Count; i++) {
		constraint_obj = &object->Package.Elements[i];
		constraint = &sc->constraints[j];

		constraint->enabled =
		    constraint_obj->Package.Elements[1].Integer.Value;

		name_obj = &constraint_obj->Package.Elements[0];
		constraint->name = strdup(name_obj->String.Pointer, M_TEMP);

		detail = &constraint_obj->Package.Elements[2];
		/*
		 * The first element in the device constraint detail package is
		 * the revision, and should always be zero.
		 */
		revision = detail->Package.Elements[0].Integer.Value;
		if (revision != 0) {
			/* Only print this error message once if not verbose. */
			if (VERBOSE() || sc->constraint_count ==
			    object->Package.Count)
				device_printf(sc->dev,
				    "Intel: Unknown revision %d for "
				    "constraint %zu's detail package\n",
				    revision, i);
			sc->constraint_count--;
			continue;
		}

		constraint_package = &detail->Package.Elements[1];

		constraint->lpi_uid =
		    constraint_package->Package.Elements[0].Integer.Value;
		constraint->min_d_state =
		    constraint_package->Package.Elements[1].Integer.Value;
		constraint->min_dev_specific_state =
		    constraint_package->Package.Elements[2].Integer.Value;

		j++;
	}

	return (0);
}

static int
acpi_spmc_parse_constraints_amd(struct acpi_spmc_softc *sc, ACPI_OBJECT *object)
{
	size_t		constraint_count;
	ACPI_OBJECT	*constraint_obj;
	ACPI_OBJECT	*constraints;
	struct acpi_spmc_constraint *constraint;
	ACPI_OBJECT	*name_obj;

	/*
	 * First element in the package is unknown.
	 * Second element is the number of device constraints.
	 * Third element is the list of device constraints itself.
	 */
	constraint_count = object->Package.Elements[1].Integer.Value;
	constraints = &object->Package.Elements[2];

	if (constraints->Package.Count != constraint_count) {
		device_printf(sc->dev,
		    "AMD: Constraints: Count mismatch (%d to %zu)\n",
		    constraints->Package.Count, constraint_count);
		return (ENXIO);
	}

	sc->constraint_count = constraint_count;
	sc->constraints = malloc(constraint_count * sizeof *sc->constraints,
	    M_TEMP, M_WAITOK | M_ZERO);

	for (size_t i = 0; i < constraint_count; i++) {
		/* Parse the constraint package. */
		constraint_obj = &constraints->Package.Elements[i];
		if (constraint_obj->Package.Count != 4) {
			device_printf(sc->dev,
			    "AMD: Constraint %zu has %d elements, not 4\n",
			    i, constraint_obj->Package.Count);
			acpi_spmc_free_constraints(sc);
			return (ENXIO);
		}

		constraint = &sc->constraints[i];
		constraint->enabled =
		    constraint_obj->Package.Elements[0].Integer.Value;

		name_obj = &constraint_obj->Package.Elements[1];
		constraint->name = strdup(name_obj->String.Pointer, M_TEMP);

		constraint->function_states =
		    constraint_obj->Package.Elements[2].Integer.Value;
		constraint->min_d_state =
		    constraint_obj->Package.Elements[3].Integer.Value;
	}

	return (0);
}

static int
acpi_spmc_get_constraints(struct acpi_spmc_softc *const sc)
{
	const struct dsm_desc *dsm;
	ACPI_STATUS status;
	ACPI_BUFFER result;
	ACPI_OBJECT *object;
	int rv;
	struct acpi_spmc_constraint *constraint;


	MPASS(!sc->get_constraints_succeeded);
	/*
	 * Constraints are not supported by the Microsoft DSM.  Since we do not
	 * expect both Intel and AMD DSMs to be present at once, we only have
	 * a single storage for common information ('min_d_state').  In case
	 * some day both happen to be present, warn the user so that he can
	 * report that condition to us, and somewhat arbitrarily favor the Intel
	 * one because it at least has a written specification.
	 */
	if (supports_function(sc, DSM_INTEL, DSM_GET_DEVICE_CONSTRAINTS)) {
		dsm = &dsm_intel;

		if (supports_function(sc, DSM_AMD, DSM_GET_DEVICE_CONSTRAINTS))
			device_printf(sc->dev, "Constraints: Both Intel and "
			    "AMD DSMs support getting them!\n"
			    "Using constraints from Intel.\nPlease report.\n");
	} else if (supports_function(sc, DSM_AMD, DSM_GET_DEVICE_CONSTRAINTS))
		dsm = &dsm_amd;
	else
		return (0);

	/* It seems like this DSM can fail if called more than once. */
	status = acpi_EvaluateDSMTyped(sc->handle, (const uint8_t *)&dsm->uuid,
	    get_revision(sc, dsm->index), DSM_GET_DEVICE_CONSTRAINTS, NULL,
	    &result, ACPI_TYPE_PACKAGE);
	if (ACPI_FAILURE(status)) {
		failed_to_call_dsm(sc, dsm, DSM_GET_DEVICE_CONSTRAINTS);
		return (ENXIO);
	} else if (VERBOSE())
		device_printf(sc->dev, "Constraints: Retrieved successfully\n");

	object = (ACPI_OBJECT *)result.Pointer;
	if (dsm == &dsm_intel)
		rv = acpi_spmc_parse_constraints_intel(sc, object);
	else {
		MPASS(dsm == &dsm_amd);
		rv = acpi_spmc_parse_constraints_amd(sc, object);
	}
	AcpiOsFree(object);
	if (rv != 0)
		return (rv);

	/* Get handles for each constraint device. */
	for (size_t i = 0; i < sc->constraint_count; i++) {
		constraint = &sc->constraints[i];

		status = acpi_GetHandleInScope(sc->handle, constraint->name,
		    &constraint->handle);
		if (ACPI_FAILURE(status)) {
			if (VERBOSE())
				device_printf(sc->dev,
				    "Constraints: Cannot get handle for %s, "
				    "ignoring\n",
				    constraint->name);
			constraint->handle = NULL;
		}
	}

#ifdef INVARIANTS
	sc->get_constraints_succeeded = true;
#endif
	return (0);
}

static void
acpi_spmc_check_constraints(device_t dev)
{
	const struct acpi_spmc_softc *const sc = device_get_softc(dev);
#ifdef notyet
	bool violation = false;
#endif

	/*
	 * Avoid printing that constraints are respected when there are no
	 * constraints at all.
	 */
	if (sc->constraint_count == 0)
		return;
	for (size_t i = 0; i < sc->constraint_count; i++) {
		const struct acpi_spmc_constraint *constraint =
		    &sc->constraints[i];

		if (!constraint->enabled)
			continue;
		if (constraint->handle == NULL)
			continue;

#ifdef notyet
		int d_state;
		if (ACPI_FAILURE(acpi_pwr_get_state(constraint->handle, &d_state)))
			continue;
		if (d_state < constraint->min_d_state) {
			device_printf(sc->dev, "Constraint for device %s"
			    " violated (current D-state: %s, "
			    "required minimum D-state: %s).\n"
			    constraint->name,
			    acpi_d_state_to_str(d_state),
			    acpi_d_state_to_str(constraint->min_d_state));
			violation = true;
		}
#endif
	}
#ifdef notyet
	if (violation)
		device_printf(sc->dev, "Some constraints violated, "
		    "might fail to enter a Low-Power Idle state\n");
	else
		device_printf(sc->dev,
		    "All device power constraints respected!\n");
#endif
}

/*
 * Run a single DSM function.
 *
 * Only runs the function if it was reported present during enumeration.
 * Discards the result, but prints a message on error.
 */
static void
acpi_spmc_run(device_t dev, const struct dsm_desc *const dsm,
    const int function_index)
{
	const struct acpi_spmc_softc *const sc = device_get_softc(dev);
	ACPI_STATUS status;
	ACPI_BUFFER result;

	if (!(supports_function(sc, dsm->index, function_index) ||
	    (force_call_expected_functions && has_dsm(sc, dsm->index))))
		return;

	if (VERBOSE())
		device_printf(dev, "DSM %s: Calling function %s\n",
		    dsm->name, dsm_function_name(dsm, function_index));
	status = acpi_EvaluateDSMTyped(sc->handle, (const uint8_t *)&dsm->uuid,
	    get_revision(sc, dsm->index), function_index, NULL,
	    &result, ACPI_TYPE_ANY);

	if (ACPI_FAILURE(status))
		failed_to_call_dsm(sc, dsm, function_index);
	else {
		if (VERBOSE())
			device_printf(dev, "DSM %s: Function %s successful\n",
			    dsm->name, dsm_function_name(dsm, function_index));
		AcpiOsFree(result.Pointer);
	}
}

/*
 * Try running the functions from all the DSMs we have, as them failing costs us
 * nothing, and it seems like on AMD platforms, both the AMD entry and Microsoft
 * "modern" functions are required for it to enter modern standby.
 *
 * This is what Linux does too.
 */
static void
acpi_spmc_display_off_notif(device_t dev)
{
	acpi_spmc_run(dev, &dsm_intel, DSM_INTEL_MS_DISPLAY_OFF_NOTIF);
	acpi_spmc_run(dev, &dsm_ms, DSM_INTEL_MS_DISPLAY_OFF_NOTIF);
	acpi_spmc_run(dev, &dsm_amd, DSM_AMD_DISPLAY_OFF_NOTIF);
}

static void
acpi_spmc_display_on_notif(device_t dev)
{
	acpi_spmc_run(dev, &dsm_intel, DSM_INTEL_MS_DISPLAY_ON_NOTIF);
	acpi_spmc_run(dev, &dsm_ms, DSM_INTEL_MS_DISPLAY_ON_NOTIF);
	acpi_spmc_run(dev, &dsm_amd, DSM_AMD_DISPLAY_ON_NOTIF);
}

static void
acpi_spmc_entry_notif(device_t dev)
{
	/* XXX - No real check currently. Check return code when it does. */
	acpi_spmc_check_constraints(dev);

	acpi_spmc_run(dev, &dsm_amd, DSM_AMD_LPI_ENTRY_NOTIF);
	acpi_spmc_run(dev, &dsm_ms, DSM_MS_SLEEP_ENTRY_NOTIF);
	acpi_spmc_run(dev, &dsm_ms, DSM_INTEL_MS_LPI_ENTRY_NOTIF);
	acpi_spmc_run(dev, &dsm_intel, DSM_INTEL_MS_LPI_ENTRY_NOTIF);
}

static void
acpi_spmc_exit_notif(device_t dev)
{
	acpi_spmc_run(dev, &dsm_intel, DSM_INTEL_MS_LPI_EXIT_NOTIF);
	acpi_spmc_run(dev, &dsm_amd, DSM_AMD_LPI_EXIT_NOTIF);
	acpi_spmc_run(dev, &dsm_ms, DSM_INTEL_MS_LPI_EXIT_NOTIF);
	/* Hint to the platform we are soon going to turn on the display. */
	acpi_spmc_run(dev, &dsm_ms, DSM_MS_TURN_ON_DISPLAY);
	acpi_spmc_run(dev, &dsm_ms, DSM_MS_SLEEP_EXIT_NOTIF);
}

static void
acpi_spmc_suspend(device_t dev, enum power_stype stype)
{
	if (stype != POWER_STYPE_SUSPEND_TO_IDLE)
		return;

	acpi_spmc_display_off_notif(dev);
	acpi_spmc_entry_notif(dev);
}

static void
acpi_spmc_resume(device_t dev, enum power_stype stype)
{
	if (stype != POWER_STYPE_SUSPEND_TO_IDLE)
		return;

	acpi_spmc_exit_notif(dev);
	acpi_spmc_display_on_notif(dev);
}

static device_method_t acpi_spmc_methods[] = {
	DEVMETHOD(device_probe,		acpi_spmc_probe),
	DEVMETHOD(device_attach,	acpi_spmc_attach),
	DEVMETHOD(device_detach,	acpi_spmc_detach),
	DEVMETHOD_END
};

static driver_t acpi_spmc_driver = {
	"acpi_spmc",
	acpi_spmc_methods,
	sizeof(struct acpi_spmc_softc),
};

DRIVER_MODULE_ORDERED(acpi_spmc, acpi, acpi_spmc_driver, NULL, NULL, SI_ORDER_ANY);
MODULE_DEPEND(acpi_spmc, acpi, 1, 1, 1);