Neo 1973 GTA01 Power Management

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Power management is of utmost concern to any mobile device. Battery power is quite limited, so we need to make sure we try our best to conserve it. The Neo1973 Power Management page tries to describe the various power management features of the Neo1973 Hardware, their states, transitions, etc. First, we start by describing the power states of the individual hardware components. Then we look at it from a System Integration point of view.

S3C2410 SoC

The S3C2410 SoC section is an overview of the S3C2410 power states or modes and their capabilities. The S3C2410 has the following modes:

• Normal Mode
• Idle Mode
• Slow Mode
• Power_off Mode

Normal Mode

This is the most power-consuming mode. Regular operation at full clock speed (266MHz). The typical power consumption is 335mW in this mode.

We can dynamically reduce the CPU core clock speed to lower frequencies, if required.

Idle Mode

In this mode, FCLK to the CPU core is switched off. This reduces the power consumption to about half the typical 'Normal mode' consumption: 177mW

Wake-up sources

any interrupt.

Slow Mode

In slow mode, FCLK is tied to the external crystal, i.e. 12MHz in our case. The CPU core, SDRAM and bus clocks are also running at 12MHz.

This reduces the power consumption to typically 33mW.

Wake-up sources

none, we can just use our slowly running code to switch back to Normal mode, if it's required.

Power_off Mode

In Power_off mode, only the SDRAM is held in refresh, and the SoC-internal wake-up logic and RTC is powered. This means that the overall power consumption of the CPU goes down to max. 100uA, which translates to 200uW at 2.0V core voltage.

Wake-up sources

The number of wake-up sources is more restricted in this mode:

• EINT[0...15]
• RTC Alarm Interrupt
• nBATT_FAULT pin

System design considerations

In order to fully support Power_off mode, we need to

• Be able to switch off VDDi/VDDiarm/VDDi_MPLL/VDDi_UPLL separately from VDDalive, using a switch based on the PWREN signal

PCF50606 PMU

This is an overview of the PCF50606 power modes / state transitions

NOPOWER

Condition: Vbat < Vverylowbat && Vback < Vlowback && Vchgvin < Vlowchg

Human-Readable: If main battery voltage < 2.7V and backup battery voltage < 1.3V and charger voltage < 2.7V

SAVE

Condition: Vbat < Vverylowbat && (Vback > Vlowback || Vchgvin > Vlowchg)

Human-readable: If main battery voltage < 2.7V and at least backup battery voltage > 1.3V or charger voltage > 2.7V.

STANDBY

Condition: Vbat > Vverylowbat

Human-readable: If main battery voltage > 2.7V

ACTIVE

Condition: Vbat > Vlowbat Human-Readable: If main battery voltage > 2.8V (configurable up to 3.4V) Transition from STANDBY to ACTIVE: If ONKEY button is pressed, or RTC Alarm, or EXTON or charger insert or pen-down by touchscreen (we don't use the PMU TS controller)

JBT6K74 LCM

Deep Standby

In this mode, only the supply power is activated

Sleep

Holds register data with clock stopped

Normal

Fully powered up and operational

System Level

This is a description of the system-level power management.

System Power states

In order to do system-level power managment, we need to introduce state definitions with their according state names. The state names are prefixed by SYS_POWER_.

SYS_POWER_NO

In this state, there is no main battery and no USB charger voltage applied. However, the backup battery is supposed to be operational.

• PCF50606: SAVE
• S3C2410: unpowered
• JBT6K74: unpowered by PMU
• GSM: unpovered because no Vbatt
• GPS: unpowered by PMU
• Bluetooth: unpowered by PMU
• Backlight: powered off

SYS_POWER_OFF

This is the regular, "switched off" state of the device. The device does not provide any functionality.

• PCF50606: STANDBY
• S3C2410: unpowered by PMU
• GSM: Powered down by driving MODEM_ON to LOW
• GPS: unpowererd by PMU
• JBT6K74: unpowered by PMU
• Bluetooth: unpowered by PMU
• Backlight: powered off

SYS_POWER_ON_FULL

This is the regular, "fully switched on" state of the device, during user interaction.

• PCF50606: ACTIVE
• S3C2410: NORMAL
• GSM: Powered up by driving MODEM_ON to HIGH
• GPS: Depending usage / configuration
• Bluetooth: Depending usage / configuration
• JBT6K74: NORMAL
• Backlight: on (brightness according to PWM)

SYS_POWER_ON_SCRSAVE

This is the screen saver mode, if user doesn't interact with LCM for some time (SCRSAVE_TIMEOUT), default 30sec.

• PCF50606: ACTIVE
• S3C2410: SLOW or IDLE
• GSM: Powered up by driving MODEM_ON to HIGH
• GPS: Depending usage / configuration
• Bluetooth : Depending usage / configuration
• JBT6K74: SLEEP
• Backlight: powered off

SYS_POWER_SLEEP

This is the power saving mode, if user doesn't interact with LCM within SLEEP_TIMEOUT after SYS_POWER_ON_SCRSAVE was entered, default 30sec.

• PCF50606: ACTIVE
• S3C2410: Power_off (this is the suspend-to-RAM state)
• GSM: Powered up by driving MODEM_ON to HIGH
• GPS: TBD
• Bluetooth: Powered down by PMU
• JBT6K74: Deep Standby
• Backlight: powered off

Wake-up reasons

In the following events, we want the main CPU to be able to be woken up from Power_off (SYS_POWER_SLEEP) state:

Events from GSM

• Incoming phone call
• Incoming SMS
• Loss of network signal

Implementation

The GSM daemon configures the GSM Modem in a way to only report the required unsolicited result codes to the UART. The CPU then needs to wake-up as soon as characters arrive at the UART.

NOTE: The S3C2410 cannot resume from Power_off on UART input data. We need to connect either RTS/CTS to EINT, or send some other signals via GSM Modem GPIO to the EINT[0..15] pins of the S3C2410

Button Press

If somebody pushes either the Neo1973 Aux Button or the Neo1973 Power Button, the system shall wake up

Implementation

Power Button

During suspend, the PMU is configured to allow PWRONF events to generate interrupts to the CPU.

NOTE: Currently, the PMU IRQ is connected to EINT16, i.e. an interrupt source that cannot wake-up from Power_off mode!

911 Button

The 911 button is connected to a EINT source that can wake-up the CPU from Poewer_off.

This means that resuming on 911 button will work out-of-the-box

Charger Events

If a charger plug (or any other USB device) is connected, the device shall resume and update the battery [charger] status. Also, charger errors such as over/undervoltage, over/under-temperature shall be reported.

Implementation

During suspend, the PMU is configured to allow EXTONR,CHGERR and related events to generate interrupts to the CPU.

NOTE: Currently, the PMU IRQ is connected to EINT16, i.e. an interrupt source that cannot wake-up from Power_off mode!

Voltages

VB

• Battery terminal voltage
• Used by
  • LM4857 Amplifier
  • PCF50606 PMU
  • LCM Backlight
  • U7607 AVDD regulator
  • U7608 VTXCO_2V8 regulator

CORE_1V8

This is the S3C2410 Core Voltage

• Generated by PMU DCUD

IO_3V3

• Generated by PMU DCDE
• Used by
  • Vibrator
  • FLASH_3V3 (see below)
  • Touch panel transistors
  • S3C2410 VDDA_ADC
  • S3C2410 VDDOP
  • S3C2410 VDDMOP
  • S3C2410 nBATT_FLT
  • U1502 (latch for GSM UART)
  • S3C2410 EXTCLK ???
  • SDRAM

GL_3V3

• Generated by PMU DCDF

• Used by
  • AGPS

• Controlled by
  • PMU

PM Driver

• Switch on/off if GPS is used or not

Initial state

• disabled by u-boot PMU initialization

CODEC_3V3

• Generated by PMU IOVDD

• Used for
  • Audio Codec (digital and analog)

• Controlled by
  • PMU Driver

PM Driver

• mostly included in ASoC, right?
• switch on, only if Audio path is required.

Initial state

• disabled by PMU initialization in u-boot

LCM_3V3

• Generated by PMU LPVDDD

• Used by
  • Headset/GSM Uart Latch
  • LCM

PM Driver

• check whether we really need to switch this off, since LCM has sophisticated PM features

Initial state

• enabled by u-boot PMU initialization

BT_3V15

• Generated by PMU D1REG

PM Driver

• has to be powered up before Bluetooth can be used
• Bluetooth device automatically enumerates at bus

Initial state

• disabled by u-boot PMU initialization

GL_2V5

• Generated by PMU D2REG

• Used by
  • AGPS

• Controlled by
  • PMU Driver

PM Driver

• switch on only in case GPS is enabled

Initial state

• disable by u-boot GPIO initialization

USER1

FIXME: no idea what this is for

• Generated by PMU D3REG

PMU Driver

• permanently disabled

Initial state

• disabled by PMU initialization in u-boot

FLASH_3V3

• Derived from IO_3V3

• Used by
  • NAND Flash

• Controlled by
  • SD_EN GPIO

PM Driver

• do we really want to switch it on/off before every flash access?
• if we go to standby, IO_3V3 will be switched off, thus FLASH_3V3 is off, too

Initial state

• on, enabled by u-boot GPIO initialization

AVDD

• Generated by U6707

• Used by
  • AGPS

• Controlled by
  • EN_AGPS3V GPIO

PM Driver

• Switch on only if GPS enabled

VTCXO_2V8

• Generated by U7608

• Used by
  • AGPS

• Controlled by
  • EN_GPS2V8 GPIO

PM Driver

• enable only if GPS is used.

Initial State

• disabled by u-boot GPIO initialization

SD_3V3

• Derived from IO_3V3

• Used by
  • microSD slot

• Controlled by
  • SD_ON GPIO

PM Driver

• we don't want to switch this off while mounted, do we?

Initial state

• probably disabled, unless somebody uses 'mmcinit' from u-boot
• but we can't disable it without disabling NAND.
• result: enabled by u-boot GPIO initialization

Kernel API

Userspace API

Approximate power draw of various subsystems

The battery has a total of 1200mAh, at 3.6V. This is approximately 3500mWh, once power supply losses are taken into account. The figues below are estimates from datasheets.

These do not take into account the severe hardware bugs of phase 0 hardware, which severely affect power use.

• LCD
  • 200mW with backlight at full brightness
  • 40mW with backlight at 10%
    • Based on similar 2.8" LCDs.
• CPU
  • 320mW @ 200MHz
  • 450mW @ 266MHz
  • 140mW @ 200MHz idle.
  • 50mW @ 12MHz (slow mode)
    • These include fudge factors for RAM and other systems, from the CPU datasheet.
• Bluetooth
  • 63mW @ Tx Burst (file transfer, send)
  • 36mW @ Rx Burst (file transfer, receive)
  • 3.6mW @ Idle, beacon only
    • Based on the datasheets provided
• GSM ?
  • • All GSM terminals have a 2W radio trasmitter so I believe Tx burst consumption will be under that while Rx burst and idle values should be in the 30mW range.
• GPS
  • 45mW
    • Based on comparison with a broadly similar (though not as fully featured chip from Maxim

USB does not work in slow mode, nor does the LCD screen controller. It is not impossible that there may be ways to draw on the screen through the SPI interface, but this has not been confirmed or documented. As bluetooth is connected via an internal USB connector, this will not work either.

This would imply that with the CPU constantly on in low power mode, GPS and GSM blipping on and off, and display off, the worst case power consumption is probably around 70mW, leading to a battery life of 2 days. If the CPU is turned off, battery life rises significantly.

With everything on, playing video with sound, for example should get well over 4 hours.

Measured power draw on phase 0 neo1973

I played with old ampermeter, old nokia 3110 (as a powersupply) and phase0 neo1973 a bit. It appears to eat 1.02 mW while powered off, 1.02W while booted (backlight on), ~0.51W while sleeping (with backlight on) and 1.4W while loading applications.

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