drivers/firmware/psci.c - u-boot - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (C) 2017 Masahiro Yamada <yamada.masahiro@socionext.com>
  *
  * Based on drivers/firmware/psci.c from Linux:
  * Copyright (C) 2015 ARM Limited
  */

 #include <command.h>
 #include <dm.h>
 #include <efi_loader.h>
 #include <irq_func.h>
 #include <linker_lists.h>
 #include <log.h>
 #include <sysreset.h>
 #include <asm/system.h>
 #include <dm/device-internal.h>
 #include <dm/lists.h>
 #include <linux/arm-smccc.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/libfdt.h>
 #include <linux/printk.h>
 #include <linux/psci.h>
 #include <power-domain-uclass.h>

 #define DRIVER_NAME "psci"

 #define PSCI_METHOD_HVC 1
 #define PSCI_METHOD_SMC 2

 /*
  * While a 64-bit OS can make calls with SMC32 calling conventions, for some
  * calls it is necessary to use SMC64 to pass or return 64-bit values.
  * For such calls PSCI_FN_NATIVE(version, name) will choose the appropriate
  * (native-width) function ID.
  */
 #if defined(CONFIG_ARM64)
 #define PSCI_FN_NATIVE(version, name)	PSCI_##version##_FN64_##name
 #else
 #define PSCI_FN_NATIVE(version, name)	PSCI_##version##_FN_##name
 #endif

 #if CONFIG_IS_ENABLED(EFI_LOADER)
 int __efi_runtime_data psci_method;
 #else
 int psci_method __section(".data");
 #endif

 unsigned long __efi_runtime invoke_psci_fn
 		(unsigned long function_id, unsigned long arg0,
 		 unsigned long arg1, unsigned long arg2)
 {
 	struct arm_smccc_res res;

 	/*
 	 * In the __efi_runtime we need to avoid the switch statement. In some
 	 * cases the compiler creates lookup tables to implement switch. These
 	 * tables are not correctly relocated when SetVirtualAddressMap is
 	 * called.
 	 */
 	if (psci_method == PSCI_METHOD_SMC)
 		arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
 	else if (psci_method == PSCI_METHOD_HVC)
 		arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
 	else
 		res.a0 = PSCI_RET_DISABLED;
 	return res.a0;
 }

 static int request_psci_features(u32 psci_func_id)
 {
 	return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
 			      psci_func_id, 0, 0);
 }

 static u32 psci_0_2_get_version(void)
 {
 	return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
 }

 static bool psci_is_system_reset2_supported(void)
 {
 	int ret;
 	u32 ver;

 	ver = psci_0_2_get_version();

 	if (PSCI_VERSION_MAJOR(ver) >= 1) {
 		ret = request_psci_features(PSCI_FN_NATIVE(1_1,
 							   SYSTEM_RESET2));

 		if (ret != PSCI_RET_NOT_SUPPORTED)
 			return true;
 	}

 	return false;
 }

 static void smccc_invoke_hvc(unsigned long a0, unsigned long a1,
 			     unsigned long a2, unsigned long a3,
 			     unsigned long a4, unsigned long a5,
 			     unsigned long a6, unsigned long a7,
 			     struct arm_smccc_res *res)
 {
 	arm_smccc_hvc(a0, a1, a2, a3, a4, a5, a6, a7, res);
 }

 static void smccc_invoke_smc(unsigned long a0, unsigned long a1,
 			     unsigned long a2, unsigned long a3,
 			     unsigned long a4, unsigned long a5,
 			     unsigned long a6, unsigned long a7,
 			     struct arm_smccc_res *res)
 {
 	arm_smccc_smc(a0, a1, a2, a3, a4, a5, a6, a7, res);
 }

 static int bind_smccc_features(struct udevice *dev, int psci_method)
 {
 	struct psci_plat_data *pdata = dev_get_plat(dev);
 	struct arm_smccc_feature *feature;
 	size_t feature_cnt, n;

 	if (!IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES))
 		return 0;

 	/*
 	 * SMCCC features discovery invoke SMCCC standard function ID
 	 * ARM_SMCCC_ARCH_FEATURES but this sequence requires that this
 	 * standard ARM_SMCCC_ARCH_FEATURES function ID itself is supported.
 	 * It is queried here with invoking PSCI_FEATURES known available
 	 * from PSCI 1.0.
 	 */
 	if (!device_is_compatible(dev, "arm,psci-1.0") ||
 	    PSCI_VERSION_MAJOR(psci_0_2_get_version()) == 0)
 		return 0;

 	if (request_psci_features(ARM_SMCCC_VERSION) ==
 	    PSCI_RET_NOT_SUPPORTED)
 		return 0;

 	if (invoke_psci_fn(ARM_SMCCC_VERSION, 0, 0, 0) < ARM_SMCCC_VERSION_1_1)
 		return 0;

 	if (psci_method == PSCI_METHOD_HVC)
 		pdata->invoke_fn = smccc_invoke_hvc;
 	else
 		pdata->invoke_fn = smccc_invoke_smc;

 	feature_cnt = ll_entry_count(struct arm_smccc_feature, arm_smccc_feature);
 	feature = ll_entry_start(struct arm_smccc_feature, arm_smccc_feature);

 	for (n = 0; n < feature_cnt; n++, feature++) {
 		const char *drv_name = feature->driver_name;
 		struct udevice *dev2;
 		int ret;

 		if (!feature->is_supported || !feature->is_supported(pdata->invoke_fn))
 			continue;

 		ret = device_bind_driver(dev, drv_name, drv_name, &dev2);
 		if (ret) {
 			pr_warn("%s was not bound: %d, ignore\n", drv_name, ret);
 			continue;
 		}

 		dev_set_parent_plat(dev2, dev_get_plat(dev));
 	}

 	return 0;
 }

 static int psci_bind(struct udevice *dev)
 {
 #if IS_ENABLED(CONFIG_POWER_DOMAIN)
 	ofnode node;
 #endif

 	/* No SYSTEM_RESET support for PSCI 0.1 */
 	if (device_is_compatible(dev, "arm,psci-0.2") ||
 	    device_is_compatible(dev, "arm,psci-1.0")) {
 		int ret;

 		/* bind psci-sysreset optionally */
 		ret = device_bind_driver(dev, "psci-sysreset", "psci-sysreset",
 					 NULL);
 		if (ret)
 			pr_debug("PSCI System Reset was not bound.\n");
 	}

 	/* From PSCI v1.0 onward we can discover services through ARM_SMCCC_FEATURE */
 	if (IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES) && device_is_compatible(dev, "arm,psci-1.0"))
 		dev_or_flags(dev, DM_FLAG_PROBE_AFTER_BIND);

 	/* Bind power-domain subnodes */
 #if IS_ENABLED(CONFIG_POWER_DOMAIN)
 	dev_for_each_subnode(node, dev) {
 		if (device_bind_driver_to_node(dev, "psci_power_domain",
 					       ofnode_get_name(node),
 					       node, NULL))
 			pr_warn("failed to bind %s\n", ofnode_get_name(node));
 	}
 #endif

 	return 0;
 }

 static int psci_probe(struct udevice *dev)
 {
 	const char *method;

 #if defined(CONFIG_ARM64)
 	if (current_el() == 3)
 		return -EINVAL;
 #endif

 	method = ofnode_read_string(dev_ofnode(dev), "method");
 	if (!method) {
 		pr_warn("missing \"method\" property\n");
 		return -ENXIO;
 	}

 	if (!strcmp("hvc", method)) {
 		psci_method = PSCI_METHOD_HVC;
 	} else if (!strcmp("smc", method)) {
 		psci_method = PSCI_METHOD_SMC;
 	} else {
 		pr_warn("invalid \"method\" property: %s\n", method);
 		return -EINVAL;
 	}

 	return bind_smccc_features(dev, psci_method);
 }

 /**
  * void do_psci_probe() - probe PSCI firmware driver
  *
  * Ensure that psci_method is initialized.
  */
 static void __maybe_unused do_psci_probe(void)
 {
 	struct udevice *dev;

 	uclass_get_device_by_name(UCLASS_FIRMWARE, DRIVER_NAME, &dev);
 }

 #if IS_ENABLED(CONFIG_EFI_LOADER) && IS_ENABLED(CONFIG_PSCI_RESET)
 efi_status_t efi_reset_system_init(void)
 {
 	do_psci_probe();
 	return EFI_SUCCESS;
 }

 void __efi_runtime EFIAPI efi_reset_system(enum efi_reset_type reset_type,
 					   efi_status_t reset_status,
 					   unsigned long data_size,
 					   void *reset_data)
 {
 	if (reset_type == EFI_RESET_COLD ||
 	    reset_type == EFI_RESET_WARM ||
 	    reset_type == EFI_RESET_PLATFORM_SPECIFIC) {
 		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
 	} else if (reset_type == EFI_RESET_SHUTDOWN) {
 		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 	}
 	while (1)
 		;
 }
 #endif /* IS_ENABLED(CONFIG_EFI_LOADER) && IS_ENABLED(CONFIG_PSCI_RESET) */

 #ifdef CONFIG_PSCI_RESET
 void reset_misc(void)
 {
 	do_psci_probe();
 	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
 }
 #endif /* CONFIG_PSCI_RESET */

 void psci_sys_reset(u32 type)
 {
 	bool reset2_supported;

 	do_psci_probe();

 	reset2_supported = psci_is_system_reset2_supported();

 	if (type == SYSRESET_WARM && reset2_supported) {
 		/*
 		 * reset_type[31] = 0 (architectural)
 		 * reset_type[30:0] = 0 (SYSTEM_WARM_RESET)
 		 * cookie = 0 (ignored by the implementation)
 		 */
 		invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), 0, 0, 0);
 	} else {
 		invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
 	}
 }

 void psci_sys_poweroff(void)
 {
 	do_psci_probe();

 	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 }

 #if IS_ENABLED(CONFIG_CMD_POWEROFF) && !IS_ENABLED(CONFIG_SYSRESET_CMD_POWEROFF)
 int do_poweroff(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 {
 	do_psci_probe();

 	puts("poweroff ...\n");
 	udelay(50000); /* wait 50 ms */

 	disable_interrupts();
 	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 	enable_interrupts();

 	log_err("Power off not supported on this platform\n");
 	return CMD_RET_FAILURE;
 }
 #endif

 static const struct udevice_id psci_of_match[] = {
 	{ .compatible = "arm,psci" },
 	{ .compatible = "arm,psci-0.2" },
 	{ .compatible = "arm,psci-1.0" },
 	{},
 };

 U_BOOT_DRIVER(psci) = {
 	.name = DRIVER_NAME,
 	.id = UCLASS_FIRMWARE,
 	.of_match = psci_of_match,
 	.bind = psci_bind,
 	.probe = psci_probe,
 #ifdef CONFIG_ARM_SMCCC_FEATURES
 	.plat_auto = sizeof(struct psci_plat_data),
 #endif
 	.flags = DM_FLAG_PRE_RELOC,
 };

 #if IS_ENABLED(CONFIG_POWER_DOMAIN)
 /* Accept #power-domain-cells == 0 */
 static int psci_power_domain_xlate(struct power_domain *power_domain,
 				   struct ofnode_phandle_args *args)
 {
 	return args->args_count == 0 ? 0 : -EINVAL;
 }

 static const struct power_domain_ops psci_power_ops = {
 	.of_xlate = psci_power_domain_xlate,
 };

 static int psci_power_domain_probe(struct udevice *dev)
 {
 	return 0;
 }

 U_BOOT_DRIVER(psci_power_domain) = {
 	.name = "psci_power_domain",
 	.id = UCLASS_POWER_DOMAIN,
 	.ops = &psci_power_ops,
 	.probe = psci_power_domain_probe,
 	.flags = DM_FLAG_PRE_RELOC,
 };
 #endif
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (C) 2017 Masahiro Yamada <yamada.masahiro@socionext.com>
	*
	* Based on drivers/firmware/psci.c from Linux:
	* Copyright (C) 2015 ARM Limited
	*/

	#include <command.h>
	#include <dm.h>
	#include <efi_loader.h>
	#include <irq_func.h>
	#include <linker_lists.h>
	#include <log.h>
	#include <sysreset.h>
	#include <asm/system.h>
	#include <dm/device-internal.h>
	#include <dm/lists.h>
	#include <linux/arm-smccc.h>
	#include <linux/delay.h>
	#include <linux/errno.h>
	#include <linux/libfdt.h>
	#include <linux/printk.h>
	#include <linux/psci.h>
	#include <power-domain-uclass.h>

	#define DRIVER_NAME "psci"

	#define PSCI_METHOD_HVC 1
	#define PSCI_METHOD_SMC 2

	/*
	* While a 64-bit OS can make calls with SMC32 calling conventions, for some
	* calls it is necessary to use SMC64 to pass or return 64-bit values.
	* For such calls PSCI_FN_NATIVE(version, name) will choose the appropriate
	* (native-width) function ID.
	*/
	#if defined(CONFIG_ARM64)
	#define PSCI_FN_NATIVE(version, name) PSCI_##version##_FN64_##name
	#else
	#define PSCI_FN_NATIVE(version, name) PSCI_##version##_FN_##name
	#endif

	#if CONFIG_IS_ENABLED(EFI_LOADER)
	int __efi_runtime_data psci_method;
	#else
	int psci_method __section(".data");
	#endif

	unsigned long __efi_runtime invoke_psci_fn
	(unsigned long function_id, unsigned long arg0,
	unsigned long arg1, unsigned long arg2)
	{
	struct arm_smccc_res res;

	/*
	* In the __efi_runtime we need to avoid the switch statement. In some
	* cases the compiler creates lookup tables to implement switch. These
	* tables are not correctly relocated when SetVirtualAddressMap is
	* called.
	*/
	if (psci_method == PSCI_METHOD_SMC)
	arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
	else if (psci_method == PSCI_METHOD_HVC)
	arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
	else
	res.a0 = PSCI_RET_DISABLED;
	return res.a0;
	}

	static int request_psci_features(u32 psci_func_id)
	{
	return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
	psci_func_id, 0, 0);
	}

	static u32 psci_0_2_get_version(void)
	{
	return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
	}

	static bool psci_is_system_reset2_supported(void)
	{
	int ret;
	u32 ver;

	ver = psci_0_2_get_version();

	if (PSCI_VERSION_MAJOR(ver) >= 1) {
	ret = request_psci_features(PSCI_FN_NATIVE(1_1,
	SYSTEM_RESET2));

	if (ret != PSCI_RET_NOT_SUPPORTED)
	return true;
	}

	return false;
	}

	static void smccc_invoke_hvc(unsigned long a0, unsigned long a1,
	unsigned long a2, unsigned long a3,
	unsigned long a4, unsigned long a5,
	unsigned long a6, unsigned long a7,
	struct arm_smccc_res *res)
	{
	arm_smccc_hvc(a0, a1, a2, a3, a4, a5, a6, a7, res);
	}

	static void smccc_invoke_smc(unsigned long a0, unsigned long a1,
	unsigned long a2, unsigned long a3,
	unsigned long a4, unsigned long a5,
	unsigned long a6, unsigned long a7,
	struct arm_smccc_res *res)
	{
	arm_smccc_smc(a0, a1, a2, a3, a4, a5, a6, a7, res);
	}

	static int bind_smccc_features(struct udevice *dev, int psci_method)
	{
	struct psci_plat_data *pdata = dev_get_plat(dev);
	struct arm_smccc_feature *feature;
	size_t feature_cnt, n;

	if (!IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES))
	return 0;

	/*
	* SMCCC features discovery invoke SMCCC standard function ID
	* ARM_SMCCC_ARCH_FEATURES but this sequence requires that this
	* standard ARM_SMCCC_ARCH_FEATURES function ID itself is supported.
	* It is queried here with invoking PSCI_FEATURES known available
	* from PSCI 1.0.
	*/
	if (!device_is_compatible(dev, "arm,psci-1.0") \|\|
	PSCI_VERSION_MAJOR(psci_0_2_get_version()) == 0)
	return 0;

	if (request_psci_features(ARM_SMCCC_VERSION) ==
	PSCI_RET_NOT_SUPPORTED)
	return 0;

	if (invoke_psci_fn(ARM_SMCCC_VERSION, 0, 0, 0) < ARM_SMCCC_VERSION_1_1)
	return 0;

	if (psci_method == PSCI_METHOD_HVC)
	pdata->invoke_fn = smccc_invoke_hvc;
	else
	pdata->invoke_fn = smccc_invoke_smc;

	feature_cnt = ll_entry_count(struct arm_smccc_feature, arm_smccc_feature);
	feature = ll_entry_start(struct arm_smccc_feature, arm_smccc_feature);

	for (n = 0; n < feature_cnt; n++, feature++) {
	const char *drv_name = feature->driver_name;
	struct udevice *dev2;
	int ret;

	if (!feature->is_supported \|\| !feature->is_supported(pdata->invoke_fn))
	continue;

	ret = device_bind_driver(dev, drv_name, drv_name, &dev2);
	if (ret) {
	pr_warn("%s was not bound: %d, ignore\n", drv_name, ret);
	continue;
	}

	dev_set_parent_plat(dev2, dev_get_plat(dev));
	}

	return 0;
	}

	static int psci_bind(struct udevice *dev)
	{
	#if IS_ENABLED(CONFIG_POWER_DOMAIN)
	ofnode node;
	#endif

	/* No SYSTEM_RESET support for PSCI 0.1 */
	if (device_is_compatible(dev, "arm,psci-0.2") \|\|
	device_is_compatible(dev, "arm,psci-1.0")) {
	int ret;

	/* bind psci-sysreset optionally */
	ret = device_bind_driver(dev, "psci-sysreset", "psci-sysreset",
	NULL);
	if (ret)
	pr_debug("PSCI System Reset was not bound.\n");
	}

	/* From PSCI v1.0 onward we can discover services through ARM_SMCCC_FEATURE */
	if (IS_ENABLED(CONFIG_ARM_SMCCC_FEATURES) && device_is_compatible(dev, "arm,psci-1.0"))
	dev_or_flags(dev, DM_FLAG_PROBE_AFTER_BIND);

	/* Bind power-domain subnodes */
	#if IS_ENABLED(CONFIG_POWER_DOMAIN)
	dev_for_each_subnode(node, dev) {
	if (device_bind_driver_to_node(dev, "psci_power_domain",
	ofnode_get_name(node),
	node, NULL))
	pr_warn("failed to bind %s\n", ofnode_get_name(node));
	}
	#endif

	return 0;
	}

	static int psci_probe(struct udevice *dev)
	{
	const char *method;

	#if defined(CONFIG_ARM64)
	if (current_el() == 3)
	return -EINVAL;
	#endif

	method = ofnode_read_string(dev_ofnode(dev), "method");
	if (!method) {
	pr_warn("missing \"method\" property\n");
	return -ENXIO;
	}

	if (!strcmp("hvc", method)) {
	psci_method = PSCI_METHOD_HVC;
	} else if (!strcmp("smc", method)) {
	psci_method = PSCI_METHOD_SMC;
	} else {
	pr_warn("invalid \"method\" property: %s\n", method);
	return -EINVAL;
	}

	return bind_smccc_features(dev, psci_method);
	}

	/**
	* void do_psci_probe() - probe PSCI firmware driver
	*
	* Ensure that psci_method is initialized.
	*/
	static void __maybe_unused do_psci_probe(void)
	{
	struct udevice *dev;

	uclass_get_device_by_name(UCLASS_FIRMWARE, DRIVER_NAME, &dev);
	}

	#if IS_ENABLED(CONFIG_EFI_LOADER) && IS_ENABLED(CONFIG_PSCI_RESET)
	efi_status_t efi_reset_system_init(void)
	{
	do_psci_probe();
	return EFI_SUCCESS;
	}

	void __efi_runtime EFIAPI efi_reset_system(enum efi_reset_type reset_type,
	efi_status_t reset_status,
	unsigned long data_size,
	void *reset_data)
	{
	if (reset_type == EFI_RESET_COLD \|\|
	reset_type == EFI_RESET_WARM \|\|
	reset_type == EFI_RESET_PLATFORM_SPECIFIC) {
	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
	} else if (reset_type == EFI_RESET_SHUTDOWN) {
	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
	}
	while (1)
	;
	}
	#endif /* IS_ENABLED(CONFIG_EFI_LOADER) && IS_ENABLED(CONFIG_PSCI_RESET) */

	#ifdef CONFIG_PSCI_RESET
	void reset_misc(void)
	{
	do_psci_probe();
	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
	}
	#endif /* CONFIG_PSCI_RESET */

	void psci_sys_reset(u32 type)
	{
	bool reset2_supported;

	do_psci_probe();

	reset2_supported = psci_is_system_reset2_supported();

	if (type == SYSRESET_WARM && reset2_supported) {
	/*
	* reset_type[31] = 0 (architectural)
	* reset_type[30:0] = 0 (SYSTEM_WARM_RESET)
	* cookie = 0 (ignored by the implementation)
	*/
	invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), 0, 0, 0);
	} else {
	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
	}
	}

	void psci_sys_poweroff(void)
	{
	do_psci_probe();

	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
	}

	#if IS_ENABLED(CONFIG_CMD_POWEROFF) && !IS_ENABLED(CONFIG_SYSRESET_CMD_POWEROFF)
	int do_poweroff(struct cmd_tbl cmdtp, int flag, int argc, char const argv[])
	{
	do_psci_probe();

	puts("poweroff ...\n");
	udelay(50000); /* wait 50 ms */

	disable_interrupts();
	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
	enable_interrupts();

	log_err("Power off not supported on this platform\n");
	return CMD_RET_FAILURE;
	}
	#endif

	static const struct udevice_id psci_of_match[] = {
	{ .compatible = "arm,psci" },
	{ .compatible = "arm,psci-0.2" },
	{ .compatible = "arm,psci-1.0" },
	{},
	};

	U_BOOT_DRIVER(psci) = {
	.name = DRIVER_NAME,
	.id = UCLASS_FIRMWARE,
	.of_match = psci_of_match,
	.bind = psci_bind,
	.probe = psci_probe,
	#ifdef CONFIG_ARM_SMCCC_FEATURES
	.plat_auto = sizeof(struct psci_plat_data),
	#endif
	.flags = DM_FLAG_PRE_RELOC,
	};

	#if IS_ENABLED(CONFIG_POWER_DOMAIN)
	/* Accept #power-domain-cells == 0 */
	static int psci_power_domain_xlate(struct power_domain *power_domain,
	struct ofnode_phandle_args *args)
	{
	return args->args_count == 0 ? 0 : -EINVAL;
	}

	static const struct power_domain_ops psci_power_ops = {
	.of_xlate = psci_power_domain_xlate,
	};

	static int psci_power_domain_probe(struct udevice *dev)
	{
	return 0;
	}

	U_BOOT_DRIVER(psci_power_domain) = {
	.name = "psci_power_domain",
	.id = UCLASS_POWER_DOMAIN,
	.ops = &psci_power_ops,
	.probe = psci_power_domain_probe,
	.flags = DM_FLAG_PRE_RELOC,
	};
	#endif