apex-monitor/apex_manager.cc - chromiumos/platform/cfm-device-monitor - Git at Google

 // Copyright 2018 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "cfm-device-monitor/apex-monitor/apex_manager.h"

 #include <base/files/file_path.h>
 #include <base/files/file_util.h>
 #include <base/files/scoped_file.h>
 #include <base/logging.h>
 #include <base/strings/stringprintf.h>

 #include <fcntl.h>

 #include <string>
 #include <utility>

 #include "cfm-device-monitor/apex-monitor/i2c_interface.h"

 namespace {

 const size_t kByteDataSize = 1;
 const size_t kWordDataSize = 2;

 // Thermal sensor CSRs.
 const uint8_t kThermalSensorPageNumber = 0x00;
 // Thermal sensor clock enable: bit 7 of 0xd0.
 const uint8_t kThermalSensorClkEnAddr = 0xd0;
 const uint8_t kThermalSensorClkEnBit = 0x7;
 // Thermal sensor ports enable: last 3 bit of 0xd8.
 const uint8_t kThermalSensorPortEnAddr = 0xd8;
 const uint8_t kThermalSensorPortEnadBit = 0x2;
 const uint8_t kThermalSensorPortEnvrBit = 0x1;
 const uint8_t kThermalSensorPortEnbgBit = 0x0;
 // Thermal sensor OMC controller enable: bit 0 of 0xdc.
 const uint8_t kThermalSensorCtrlEnAddr = 0xdc;
 const unsigned char kThermalSensorCtrlEnBit = 0x0;
 // Temperature data: 10 bits starting at 0xde.
 const uint8_t kThermalSensorTempAddr = 0xde;
 const uint16_t kThermalSensorTempMask = 0x03ff;
 // If temperature < -50C. It's more likely the thermal sensor is
 // not configured properly.
 const int kThermalLowestThreshold = -50;

 const uint32_t kEnableThermalControllerSlpTimeUs = 1e5;

 // IO expander.
 const uint8_t kApexResetSetAddr[] = {0x02, 0x03};
 // Reset bits are bit 03 and 15.
 const uint8_t kApexResetSetBits[] = {0x03, 0x05};
 // Wait 100ms before release reset signal.
 const uint32_t kApexResetSlpTimeUs = 100e3;
 // IO expander IO configuration registers.
 const uint8_t kIoExpanderIoConfig0Addr = 0x06;
 const uint8_t kIoExpanderIoConfig1Addr = 0x07;
 const unsigned char kIoExpanderIoConfig0Value = 0x67;
 const unsigned char kIoExpanderIoConfig1Value = 0xdc;
 // Apex power/boot state bits.
 const uint8_t kIoExpanderPowerStateAddr = 0x01;
 const unsigned char kApexPowerStateBitMask[] = {0x40, 0x80};
 const uint8_t kIoExpanderBootStateAddr[] = {0x00, 0x01};
 const unsigned char kApexBootStateBitMask[] = {0x01, 0x04};

 // Power control GPIOs.
 const char kSysfsGpioPath[] = "/sys/class/gpio/";
 constexpr int kApexPowerCtrlGpioId[] = {416, 417};
 const char kGpioDirOutStr[] = "out";
 const char kGpioValueHigh = '1';
 const char kGpioValueLow = '0';
 const size_t kGpioDirOutStrLen = 3;
 const size_t kGpioValueLen = 1;
 // Wait 1s for power cycle.
 const uint32_t kApexPowerCycleSlpTimeUs = 1e6;

 }  // namespace

 namespace apex_monitor {

 ApexManager::ApexManager(const int& chip_id,
                          std::unique_ptr<BaseI2cInterface> apex_interface,
                          BaseI2cInterface* ioexp_interface)
     : chip_id_(chip_id),
       apex_i2c_interface_(std::move(apex_interface)),
       io_expander_interface_(ioexp_interface) {}

 ApexManager::~ApexManager() {}

 std::unique_ptr<ApexManager> ApexManager::Create(
     const int& chip_id, std::unique_ptr<BaseI2cInterface> apex_interface,
     BaseI2cInterface* ioexp_interface) {
   auto apex_manager = std::make_unique<ApexManager>(
       chip_id, std::move(apex_interface), ioexp_interface);
   if (!apex_manager->InitThermalSensor()) {
     LOG(ERROR) << "Failed to init thermal sensor for chip " << chip_id;
     return nullptr;
   }

   return apex_manager;
 }

 bool ApexManager::InitThermalSensor() {
   // Enable thermal sensor clock.
   if (!apex_i2c_interface_->SetBit(kThermalSensorClkEnAddr,
                                    kThermalSensorClkEnBit,
                                    kThermalSensorPageNumber)) {
     LOG(ERROR) << "Failed to enable thermal sensor clock.";
     return false;
   }

   // Enable thermal sensor input port: ENBG, ENVR, ENAD.
   if (!(apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
                                     kThermalSensorPortEnadBit,
                                     kThermalSensorPageNumber) &&
         apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
                                     kThermalSensorPortEnvrBit,
                                     kThermalSensorPageNumber) &&
         apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
                                     kThermalSensorPortEnbgBit,
                                     kThermalSensorPageNumber))) {
     LOG(ERROR) << "Failed to enable thermal sensor input ports.";
     return false;
   }

   usleep(kEnableThermalControllerSlpTimeUs);

   // Enable OMC thermal sensor controller.
   if (!apex_i2c_interface_->SetBit(kThermalSensorCtrlEnAddr,
                                    kThermalSensorCtrlEnBit,
                                    kThermalSensorPageNumber)) {
     LOG(ERROR) << "Failed to enable thermal sensor controller.";
     return false;
   }

   return true;
 }

 bool ApexManager::InitIoExpander(BaseI2cInterface* ioexp_interface) {
   if (!ioexp_interface->I2cWriteReg(kIoExpanderIoConfig0Addr,
                                     &kIoExpanderIoConfig0Value,
                                     kByteDataSize)) {
     LOG(ERROR) << "Failed to configure IO expander byte 0.";
     return false;
   }

   if (!ioexp_interface->I2cWriteReg(kIoExpanderIoConfig1Addr,
                                     &kIoExpanderIoConfig1Value,
                                     kByteDataSize)) {
     LOG(ERROR) << "Failed to configure IO expander byte 1.";
     return false;
   }

   return true;
 }

 bool ApexManager::InitIoExpander() {
   if (!InitIoExpander(io_expander_interface_)) {
     LOG(ERROR) << "Failed to init IO expander.";
     return false;
   }

   return true;
 }

 bool ApexManager::IoExpanderConfigGood() {
   unsigned char config_data;
   if (!io_expander_interface_->I2cReadReg(kIoExpanderIoConfig0Addr,
                                           &config_data, kByteDataSize)) {
     LOG(ERROR) << "Failed to read IO expander configuration byte 0.";
     return false;
   }
   if (config_data != kIoExpanderIoConfig0Value) return false;

   if (!io_expander_interface_->I2cReadReg(kIoExpanderIoConfig1Addr,
                                           &config_data, kByteDataSize)) {
     LOG(ERROR) << "Failed to read IO expander configuration byte 1.";
     return false;
   }
   if (config_data != kIoExpanderIoConfig1Value) return false;

   return true;
 }

 bool ApexManager::CheckStatusRegister(bool* power_good, bool* boot_fail) {
   unsigned char read_data;
   // Read power status.
   if (!io_expander_interface_->I2cReadReg(kIoExpanderPowerStateAddr, &read_data,
                                           kByteDataSize)) {
     LOG(ERROR) << "Failed to read power status.";
     return false;
   }
   *power_good = read_data & kApexPowerStateBitMask[chip_id_];

   // If power_good is false, check boot status doesn't make any sense.
   if (!power_good) {
     *boot_fail = true;
     return true;
   }

   // Read boot status. The register address of boot status and power status
   // are the same for apex chip 1. So no need to re-read the register data
   // in that case.
   if (kIoExpanderBootStateAddr[chip_id_] != kIoExpanderPowerStateAddr) {
     if (!io_expander_interface_->I2cReadReg(kIoExpanderBootStateAddr[chip_id_],
                                             &read_data, kByteDataSize)) {
       LOG(ERROR) << "Failed to read boot status.";
       return false;
     }
   }
   *boot_fail = read_data & kApexBootStateBitMask[chip_id_];

   return true;
 }

 int ApexManager::ChipID() { return chip_id_; }

 bool ApexManager::ReadChipTemp(int* temp) {
   uint16_t temp_data;
   if (!apex_i2c_interface_->I2cReadReg(
           kThermalSensorTempAddr, reinterpret_cast<unsigned char*>(&temp_data),
           kWordDataSize, kThermalSensorPageNumber)) {
     LOG(ERROR) << "Failed to read temperature of Apex " << chip_id_;
     return false;
   }
   TempCodeToCelsius(temp_data, temp);

   // If the temprature is too low, it more likely that the thermal
   // sensor configuration is wrong.
   if (*temp < kThermalLowestThreshold) {
     InitThermalSensor();
     return true;
   }

   LOG(INFO) << "Apex chip " << chip_id_ << " temperature: " << *temp;

   return true;
 }

 inline void ApexManager::TempCodeToCelsius(const uint16_t& temp_code,
                                            int* temp) {
   *temp = static_cast<int>(
       (((662.0 - (temp_code & kThermalSensorTempMask)) / 4.0 + 0.5) * 10.0 +
        0.5) /
       10);
 }

 bool ApexManager::ResetChip() {
   // First check IO expander IO configuration.
   if (!IoExpanderConfigGood()) {
     if (!InitIoExpander()) {
       LOG(ERROR) << "Invalid IO expander IO direction configuration.";
       return false;
     }
   }

   // Assert reset signal.
   if (!io_expander_interface_->ClearBit(kApexResetSetAddr[chip_id_],
                                         kApexResetSetBits[chip_id_])) {
     LOG(ERROR) << "Failed to assert reset signal for apex " << chip_id_;
     return false;
   }

   usleep(kApexResetSlpTimeUs);

   // Release reset signal.
   if (!io_expander_interface_->SetBit(kApexResetSetAddr[chip_id_],
                                       kApexResetSetBits[chip_id_])) {
     LOG(ERROR) << "Failed to release reset signal for apex " << chip_id_;
     return false;
   }

   // Re-init thermal sensor registers.
   if (!InitThermalSensor()) {
     LOG(ERROR) << "Failed to re-init thermal sensor.";
     return false;
   }

   return true;
 }

 bool ApexManager::ExportPowerCtrlGpio() {
   std::string chip_id_str = std::to_string(kApexPowerCtrlGpioId[chip_id_]);
   base::FilePath gpio_path(kSysfsGpioPath + std::string("gpio") + chip_id_str);
   if (base::PathExists(gpio_path)) {
     VLOG(1) << "GPIO " << chip_id_str << " already exported.";
     return true;
   }

   // Export target GPIO.
   base::FilePath export_path(kSysfsGpioPath + std::string("export"));
   base::ScopedFD export_fd(
       open(export_path.value().c_str(), O_WRONLY | O_CLOEXEC));
   if (!export_fd.is_valid()) {
     LOG(ERROR) << "Failed to open " << export_path.value();
     return false;
   }

   int r = write(export_fd.get(), chip_id_str.c_str(), chip_id_str.size());
   if (r < 0 || !base::PathExists(gpio_path)) {
     PLOG(ERROR) << "Failed to export GPIO " << chip_id_str;
     return false;
   }

   r = base::WriteFile(gpio_path.Append("direction"), kGpioDirOutStr,
                       kGpioDirOutStrLen);
   if (r < 0) {
     PLOG(ERROR) << "Failed to set GPIO direction for GPIO"
                 << kApexPowerCtrlGpioId[chip_id_];
     return false;
   }

   return true;
 }

 bool ApexManager::PowerCycleChip() {
   if (!ExportPowerCtrlGpio()) {
     LOG(ERROR) << "Failed to export GPIOs to control apex power.";
     return false;
   }

   base::FilePath gpio_path(kSysfsGpioPath + std::string("gpio") +
                            std::to_string(kApexPowerCtrlGpioId[chip_id_]));

   // Power off chip.
   int r =
       base::WriteFile(gpio_path.Append("value"), &kGpioValueLow, kGpioValueLen);
   if (r < 0) {
     PLOG(ERROR) << "Failed to set GPIO " << kApexPowerCtrlGpioId[chip_id_]
                 << " value to low.";
     return false;
   }

   // Check IO expander IO configuration before toggling reset bit.
   if (!IoExpanderConfigGood()) {
     if (!InitIoExpander()) {
       LOG(ERROR) << "Invalid IO expander IO direction configuration.";
       return false;
     }
   }

   // Assert reset signal.
   if (!io_expander_interface_->ClearBit(kApexResetSetAddr[chip_id_],
                                         kApexResetSetBits[chip_id_])) {
     LOG(ERROR) << "Failed to set reset signal for apex " << chip_id_;
     return false;
   }

   usleep(kApexPowerCycleSlpTimeUs);

   // Power on chip.
   r = base::WriteFile(gpio_path.Append("value"), &kGpioValueHigh,
                       kGpioValueLen);
   if (r < 0) {
     PLOG(ERROR) << "Failed to set GPIO " << kApexPowerCtrlGpioId[chip_id_]
                 << " value to high.";
     return false;
   }

   usleep(kApexResetSlpTimeUs);

   // Release reset signal.
   if (!io_expander_interface_->SetBit(kApexResetSetAddr[chip_id_],
                                       kApexResetSetBits[chip_id_])) {
     LOG(ERROR) << "Failed to release reset signal for apex " << chip_id_;
     return false;
   }

   // Re-init thermal sensor.
   if (!InitThermalSensor()) {
     LOG(ERROR) << "Failed to re-init thermal sensor.";
     return false;
   }

   return true;
 }

 }  // namespace apex_monitor
	// Copyright 2018 The Chromium OS Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "cfm-device-monitor/apex-monitor/apex_manager.h"

	#include <base/files/file_path.h>
	#include <base/files/file_util.h>
	#include <base/files/scoped_file.h>
	#include <base/logging.h>
	#include <base/strings/stringprintf.h>

	#include <fcntl.h>

	#include <string>
	#include <utility>

	#include "cfm-device-monitor/apex-monitor/i2c_interface.h"

	namespace {

	const size_t kByteDataSize = 1;
	const size_t kWordDataSize = 2;

	// Thermal sensor CSRs.
	const uint8_t kThermalSensorPageNumber = 0x00;
	// Thermal sensor clock enable: bit 7 of 0xd0.
	const uint8_t kThermalSensorClkEnAddr = 0xd0;
	const uint8_t kThermalSensorClkEnBit = 0x7;
	// Thermal sensor ports enable: last 3 bit of 0xd8.
	const uint8_t kThermalSensorPortEnAddr = 0xd8;
	const uint8_t kThermalSensorPortEnadBit = 0x2;
	const uint8_t kThermalSensorPortEnvrBit = 0x1;
	const uint8_t kThermalSensorPortEnbgBit = 0x0;
	// Thermal sensor OMC controller enable: bit 0 of 0xdc.
	const uint8_t kThermalSensorCtrlEnAddr = 0xdc;
	const unsigned char kThermalSensorCtrlEnBit = 0x0;
	// Temperature data: 10 bits starting at 0xde.
	const uint8_t kThermalSensorTempAddr = 0xde;
	const uint16_t kThermalSensorTempMask = 0x03ff;
	// If temperature < -50C. It's more likely the thermal sensor is
	// not configured properly.
	const int kThermalLowestThreshold = -50;

	const uint32_t kEnableThermalControllerSlpTimeUs = 1e5;

	// IO expander.
	const uint8_t kApexResetSetAddr[] = {0x02, 0x03};
	// Reset bits are bit 03 and 15.
	const uint8_t kApexResetSetBits[] = {0x03, 0x05};
	// Wait 100ms before release reset signal.
	const uint32_t kApexResetSlpTimeUs = 100e3;
	// IO expander IO configuration registers.
	const uint8_t kIoExpanderIoConfig0Addr = 0x06;
	const uint8_t kIoExpanderIoConfig1Addr = 0x07;
	const unsigned char kIoExpanderIoConfig0Value = 0x67;
	const unsigned char kIoExpanderIoConfig1Value = 0xdc;
	// Apex power/boot state bits.
	const uint8_t kIoExpanderPowerStateAddr = 0x01;
	const unsigned char kApexPowerStateBitMask[] = {0x40, 0x80};
	const uint8_t kIoExpanderBootStateAddr[] = {0x00, 0x01};
	const unsigned char kApexBootStateBitMask[] = {0x01, 0x04};

	// Power control GPIOs.
	const char kSysfsGpioPath[] = "/sys/class/gpio/";
	constexpr int kApexPowerCtrlGpioId[] = {416, 417};
	const char kGpioDirOutStr[] = "out";
	const char kGpioValueHigh = '1';
	const char kGpioValueLow = '0';
	const size_t kGpioDirOutStrLen = 3;
	const size_t kGpioValueLen = 1;
	// Wait 1s for power cycle.
	const uint32_t kApexPowerCycleSlpTimeUs = 1e6;

	} // namespace

	namespace apex_monitor {

	ApexManager::ApexManager(const int& chip_id,
	std::unique_ptr<BaseI2cInterface> apex_interface,
	BaseI2cInterface* ioexp_interface)
	: chip_id_(chip_id),
	apex_i2c_interface_(std::move(apex_interface)),
	io_expander_interface_(ioexp_interface) {}

	ApexManager::~ApexManager() {}

	std::unique_ptr<ApexManager> ApexManager::Create(
	const int& chip_id, std::unique_ptr<BaseI2cInterface> apex_interface,
	BaseI2cInterface* ioexp_interface) {
	auto apex_manager = std::make_unique<ApexManager>(
	chip_id, std::move(apex_interface), ioexp_interface);
	if (!apex_manager->InitThermalSensor()) {
	LOG(ERROR) << "Failed to init thermal sensor for chip " << chip_id;
	return nullptr;
	}

	return apex_manager;
	}

	bool ApexManager::InitThermalSensor() {
	// Enable thermal sensor clock.
	if (!apex_i2c_interface_->SetBit(kThermalSensorClkEnAddr,
	kThermalSensorClkEnBit,
	kThermalSensorPageNumber)) {
	LOG(ERROR) << "Failed to enable thermal sensor clock.";
	return false;
	}

	// Enable thermal sensor input port: ENBG, ENVR, ENAD.
	if (!(apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
	kThermalSensorPortEnadBit,
	kThermalSensorPageNumber) &&
	apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
	kThermalSensorPortEnvrBit,
	kThermalSensorPageNumber) &&
	apex_i2c_interface_->SetBit(kThermalSensorPortEnAddr,
	kThermalSensorPortEnbgBit,
	kThermalSensorPageNumber))) {
	LOG(ERROR) << "Failed to enable thermal sensor input ports.";
	return false;
	}

	usleep(kEnableThermalControllerSlpTimeUs);

	// Enable OMC thermal sensor controller.
	if (!apex_i2c_interface_->SetBit(kThermalSensorCtrlEnAddr,
	kThermalSensorCtrlEnBit,
	kThermalSensorPageNumber)) {
	LOG(ERROR) << "Failed to enable thermal sensor controller.";
	return false;
	}

	return true;
	}

	bool ApexManager::InitIoExpander(BaseI2cInterface* ioexp_interface) {
	if (!ioexp_interface->I2cWriteReg(kIoExpanderIoConfig0Addr,
	&kIoExpanderIoConfig0Value,
	kByteDataSize)) {
	LOG(ERROR) << "Failed to configure IO expander byte 0.";
	return false;
	}

	if (!ioexp_interface->I2cWriteReg(kIoExpanderIoConfig1Addr,
	&kIoExpanderIoConfig1Value,
	kByteDataSize)) {
	LOG(ERROR) << "Failed to configure IO expander byte 1.";
	return false;
	}

	return true;
	}

	bool ApexManager::InitIoExpander() {
	if (!InitIoExpander(io_expander_interface_)) {
	LOG(ERROR) << "Failed to init IO expander.";
	return false;
	}

	return true;
	}

	bool ApexManager::IoExpanderConfigGood() {
	unsigned char config_data;
	if (!io_expander_interface_->I2cReadReg(kIoExpanderIoConfig0Addr,
	&config_data, kByteDataSize)) {
	LOG(ERROR) << "Failed to read IO expander configuration byte 0.";
	return false;
	}
	if (config_data != kIoExpanderIoConfig0Value) return false;

	if (!io_expander_interface_->I2cReadReg(kIoExpanderIoConfig1Addr,
	&config_data, kByteDataSize)) {
	LOG(ERROR) << "Failed to read IO expander configuration byte 1.";
	return false;
	}
	if (config_data != kIoExpanderIoConfig1Value) return false;

	return true;
	}

	bool ApexManager::CheckStatusRegister(bool* power_good, bool* boot_fail) {
	unsigned char read_data;
	// Read power status.
	if (!io_expander_interface_->I2cReadReg(kIoExpanderPowerStateAddr, &read_data,
	kByteDataSize)) {
	LOG(ERROR) << "Failed to read power status.";
	return false;
	}
	*power_good = read_data & kApexPowerStateBitMask[chip_id_];

	// If power_good is false, check boot status doesn't make any sense.
	if (!power_good) {
	*boot_fail = true;
	return true;
	}

	// Read boot status. The register address of boot status and power status
	// are the same for apex chip 1. So no need to re-read the register data
	// in that case.
	if (kIoExpanderBootStateAddr[chip_id_] != kIoExpanderPowerStateAddr) {
	if (!io_expander_interface_->I2cReadReg(kIoExpanderBootStateAddr[chip_id_],
	&read_data, kByteDataSize)) {
	LOG(ERROR) << "Failed to read boot status.";
	return false;
	}
	}
	*boot_fail = read_data & kApexBootStateBitMask[chip_id_];

	return true;
	}

	int ApexManager::ChipID() { return chip_id_; }

	bool ApexManager::ReadChipTemp(int* temp) {
	uint16_t temp_data;
	if (!apex_i2c_interface_->I2cReadReg(
	kThermalSensorTempAddr, reinterpret_cast<unsigned char*>(&temp_data),
	kWordDataSize, kThermalSensorPageNumber)) {
	LOG(ERROR) << "Failed to read temperature of Apex " << chip_id_;
	return false;
	}
	TempCodeToCelsius(temp_data, temp);

	// If the temprature is too low, it more likely that the thermal
	// sensor configuration is wrong.
	if (*temp < kThermalLowestThreshold) {
	InitThermalSensor();
	return true;
	}

	LOG(INFO) << "Apex chip " << chip_id_ << " temperature: " << *temp;

	return true;
	}

	inline void ApexManager::TempCodeToCelsius(const uint16_t& temp_code,
	int* temp) {
	*temp = static_cast<int>(
	(((662.0 - (temp_code & kThermalSensorTempMask)) / 4.0 + 0.5) * 10.0 +
	0.5) /
	10);
	}

	bool ApexManager::ResetChip() {
	// First check IO expander IO configuration.
	if (!IoExpanderConfigGood()) {
	if (!InitIoExpander()) {
	LOG(ERROR) << "Invalid IO expander IO direction configuration.";
	return false;
	}
	}

	// Assert reset signal.
	if (!io_expander_interface_->ClearBit(kApexResetSetAddr[chip_id_],
	kApexResetSetBits[chip_id_])) {
	LOG(ERROR) << "Failed to assert reset signal for apex " << chip_id_;
	return false;
	}

	usleep(kApexResetSlpTimeUs);

	// Release reset signal.
	if (!io_expander_interface_->SetBit(kApexResetSetAddr[chip_id_],
	kApexResetSetBits[chip_id_])) {
	LOG(ERROR) << "Failed to release reset signal for apex " << chip_id_;
	return false;
	}

	// Re-init thermal sensor registers.
	if (!InitThermalSensor()) {
	LOG(ERROR) << "Failed to re-init thermal sensor.";
	return false;
	}

	return true;
	}

	bool ApexManager::ExportPowerCtrlGpio() {
	std::string chip_id_str = std::to_string(kApexPowerCtrlGpioId[chip_id_]);
	base::FilePath gpio_path(kSysfsGpioPath + std::string("gpio") + chip_id_str);
	if (base::PathExists(gpio_path)) {
	VLOG(1) << "GPIO " << chip_id_str << " already exported.";
	return true;
	}

	// Export target GPIO.
	base::FilePath export_path(kSysfsGpioPath + std::string("export"));
	base::ScopedFD export_fd(
	open(export_path.value().c_str(), O_WRONLY \| O_CLOEXEC));
	if (!export_fd.is_valid()) {
	LOG(ERROR) << "Failed to open " << export_path.value();
	return false;
	}

	int r = write(export_fd.get(), chip_id_str.c_str(), chip_id_str.size());
	if (r < 0 \|\| !base::PathExists(gpio_path)) {
	PLOG(ERROR) << "Failed to export GPIO " << chip_id_str;
	return false;
	}

	r = base::WriteFile(gpio_path.Append("direction"), kGpioDirOutStr,
	kGpioDirOutStrLen);
	if (r < 0) {
	PLOG(ERROR) << "Failed to set GPIO direction for GPIO"
	<< kApexPowerCtrlGpioId[chip_id_];
	return false;
	}

	return true;
	}

	bool ApexManager::PowerCycleChip() {
	if (!ExportPowerCtrlGpio()) {
	LOG(ERROR) << "Failed to export GPIOs to control apex power.";
	return false;
	}

	base::FilePath gpio_path(kSysfsGpioPath + std::string("gpio") +
	std::to_string(kApexPowerCtrlGpioId[chip_id_]));

	// Power off chip.
	int r =
	base::WriteFile(gpio_path.Append("value"), &kGpioValueLow, kGpioValueLen);
	if (r < 0) {
	PLOG(ERROR) << "Failed to set GPIO " << kApexPowerCtrlGpioId[chip_id_]
	<< " value to low.";
	return false;
	}

	// Check IO expander IO configuration before toggling reset bit.
	if (!IoExpanderConfigGood()) {
	if (!InitIoExpander()) {
	LOG(ERROR) << "Invalid IO expander IO direction configuration.";
	return false;
	}
	}

	// Assert reset signal.
	if (!io_expander_interface_->ClearBit(kApexResetSetAddr[chip_id_],
	kApexResetSetBits[chip_id_])) {
	LOG(ERROR) << "Failed to set reset signal for apex " << chip_id_;
	return false;
	}

	usleep(kApexPowerCycleSlpTimeUs);

	// Power on chip.
	r = base::WriteFile(gpio_path.Append("value"), &kGpioValueHigh,
	kGpioValueLen);
	if (r < 0) {
	PLOG(ERROR) << "Failed to set GPIO " << kApexPowerCtrlGpioId[chip_id_]
	<< " value to high.";
	return false;
	}

	usleep(kApexResetSlpTimeUs);

	// Release reset signal.
	if (!io_expander_interface_->SetBit(kApexResetSetAddr[chip_id_],
	kApexResetSetBits[chip_id_])) {
	LOG(ERROR) << "Failed to release reset signal for apex " << chip_id_;
	return false;
	}

	// Re-init thermal sensor.
	if (!InitThermalSensor()) {
	LOG(ERROR) << "Failed to re-init thermal sensor.";
	return false;
	}

	return true;
	}

	} // namespace apex_monitor