Mainline:Broadcom Kona/BCM590xx/RTC

The RTC is located at register 0xe0 on the BCM59054/BCM59056.

Time data

The RTC stores the time in the following format:

Offset	Purpose	Value
0	Second	Current second, from 0 to 59.
1	Minute	Current minute of the hour, from 0 to 59.
2	Hour	Current hour of the day, from 0 to 23.
3	Day of month	Day of month, starting from 0.
4	Month	Number of the month. Sets itself to 0 on reset; 1 to 12 represent January-December. ...or does it? The downstream driver would suggest so, but it seems weird. Investigate.
5	Year	Amount of years since 2000 (0 = 2000, 1 = 2001, etc.)

Calibration

Downstream driver: drivers/char/broadcom/rtc_cal/bcm_rtc_cal.c

There are three calibration registers: CALIB1, CALIB2 and CALIB3.

TODO	TODO: Figure out how the calibration process works, this is just my initial idea

Calibration appears to be triggered based on a CP (communications processor) event; it receives a message from the CP and uses a value from it as the "ratio". The ratio value is then compared against RTCCAL_Ratio (taken from rtccal_data.nom_ratio, 8666667); if ratio > RTCCAL_Ratio, then direction is 1, otherwise it's 0.

The clk_val value is then calculated based on the difference between the new and old ratio (diff = abs(ratio - RTCCAL_Ratio)): clk_val = RTCCAL_Ratio / diff.

TODO - what is the ratio value?

CALIB1 (0xF4)

Name	Bit	Description
clk_val (1)	7:0	Lower 8 bits of the calibration offset.

CALIB2 (0xF5)

Name	Bit	Description
clk_val (2)	7:0	Upper 8 bits of the calibration offset.

CALIB3 (0xF6)

Name	Bit	Description
???	7	Set to 1 during calibration.
direction	6
Unknown/reserved	5:0	Unknown/reserved.