Mainline:Broadcom Kona/BCM590xx/RTC: Difference between revisions
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|- | |- | ||
|0 | |0 | ||
|Second | |Second (<code>SC</code>) | ||
|Current second, from 0 to 59. | |Current second, from 0 to 59. | ||
|- | |- | ||
|1 | |1 | ||
|Minute | |Minute (<code>MN</code>) | ||
|Current minute of the hour, from 0 to 59. | |Current minute of the hour, from 0 to 59. | ||
|- | |- | ||
|2 | |2 | ||
|Hour | |Hour (<code>HR</code>) | ||
|Current hour of the day, from 0 to 23. | |Current hour of the day, from 0 to 23. | ||
|- | |- | ||
|3 | |3 | ||
| | |Weekday (<code>WD</code>) | ||
|Day of | |Day of week; 0 is Monday, 6 is Sunday. {{speculation|todo, verify}} | ||
|- | |- | ||
|4 | |4 | ||
| | |Day of month (<code>DT</code>) | ||
| | |Day of month, starting from 0. | ||
|- | |- | ||
|5 | |5 | ||
|Year | |Month (<code>MT_WD</code>) | ||
|Number of the month. 1 to 12 represent January-December. | |||
|- | |||
|6 | |||
|Year (<code>YR</code>) | |||
|Amount of years since 2000 (0 = 2000, 1 = 2001, etc.) | |Amount of years since 2000 (0 = 2000, 1 = 2001, etc.) | ||
|} | |} | ||
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There are interrupts for updates of each of the time values. | There are interrupts for updates of each of the time values. | ||
The default reset value is 2007-01-01 at 00:00:00. | |||
== Alarm == | == Alarm == | ||
Revision as of 07:41, 14 August 2025
The BCM590XX PMUs provide a real-time clock.
Time data
The RTC stores the time in the following format:
| Offset | Purpose | Value |
|---|---|---|
| 0 | Second (SC)
|
Current second, from 0 to 59. |
| 1 | Minute (MN)
|
Current minute of the hour, from 0 to 59. |
| 2 | Hour (HR)
|
Current hour of the day, from 0 to 23. |
| 3 | Weekday (WD)
|
Day of week; 0 is Monday, 6 is Sunday. todo, verify |
| 4 | Day of month (DT)
|
Day of month, starting from 0. |
| 5 | Month (MT_WD)
|
Number of the month. 1 to 12 represent January-December. |
| 6 | Year (YR)
|
Amount of years since 2000 (0 = 2000, 1 = 2001, etc.) |
This exact format is used for both the time and alarm registers.
TODO: What happens on year overflow? Is there a reason as to why the downstream driver limits the values it gets?
Getting the time
On the BCM59054 and BCM59056, time registers start at 0xE0 and follow the format outlined above.
There are interrupts for updates of each of the time values.
The default reset value is 2007-01-01 at 00:00:00.
Alarm
On the BCM59054 and BCM59056, the alarm registers start at 0xE7.
There is an interrupt that is triggered when the alarm is triggered.
Calibration
There are three calibration registers: CALIB1, CALIB2 and CALIB3.
Page Template:Todo/style.css has no content.
| 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. |