Kernel driver da9052
  ====================

  Supported chips:

    * Dialog Semiconductors DA9052-BC and DA9053-AA/Bx PMICs

      Prefix: 'da9052'

      Datasheet: Datasheet is not publicly available.
  
  Authors: David Dajun Chen <dchen@diasemi.com>
  
  Description
  -----------
  
  The DA9052/53 provides an Analogue to Digital Converter (ADC) with 10 bits
  resolution and track and hold circuitry combined with an analogue input
  multiplexer. The analogue input multiplexer will allow conversion of up to 10
  different inputs. The track and hold circuit ensures stable input voltages at
  the input of the ADC during the conversion.
  
  The ADC is used to measure the following inputs:

  
  ========= ===================================================================
  Channel 0 VDDOUT - measurement of the system voltage
  Channel 1 ICH - internal battery charger current measurement
  Channel 2 TBAT - output from the battery NTC
  Channel 3 VBAT - measurement of the battery voltage
  Channel 4 ADC_IN4 - high impedance input (0 - 2.5V)
  Channel 5 ADC_IN5 - high impedance input (0 - 2.5V)
  Channel 6 ADC_IN6 - high impedance input (0 - 2.5V)
  Channel 7 XY - TSI interface to measure the X and Y voltage of the touch
  	  screen resistive potentiometers
  Channel 8 Internal Tjunc. - sense (internal temp. sensor)
  Channel 9 VBBAT - measurement of the backup battery voltage
  ========= ===================================================================

  
  By using sysfs attributes we can measure the system voltage VDDOUT, the battery
  charging current ICH, battery temperature TBAT, battery junction temperature
  TJUNC, battery voltage VBAT and the back up battery voltage VBBAT.
  
  Voltage Monitoring
  ------------------
  
  Voltages are sampled by a 10 bit ADC.
  
  The battery voltage is calculated as:

  	Milli volt = ((ADC value * 1000) / 512) + 2500
  
  The backup battery voltage is calculated as:

  	Milli volt = (ADC value * 2500) / 512;
  
  The voltages on ADC channels 4, 5 and 6 are calculated as:

  	Milli volt = (ADC value * 2500) / 1023
  
  Temperature Monitoring
  ----------------------
  
  Temperatures are sampled by a 10 bit ADC.  Junction and battery temperatures
  are monitored by the ADC channels.
  
  The junction temperature is calculated:

  	Degrees celsius = 1.708 * (TJUNC_RES - T_OFFSET) - 108.8

  The junction temperature attribute is supported by the driver.
  
  The battery temperature is calculated:

  
  	Degree Celsius = 1 / (t1 + 1/298) - 273

  where t1 = (1/B)* ln(( ADCval * 2.5)/(R25*ITBAT*255))

  Default values of R25, B, ITBAT are 10e3, 3380 and 50e-6 respectively.