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Subject[PATCH v3 00/14] rtc: pcf2127: add PCF2131 driver
From: Hugo Villeneuve <>

this patch series adds the driver for the PCF2131 real-time clock.

This RTC is very similar in functionality to the PCF2127/29 with the
following differences:
-supports two new control registers at offsets 4 and 5
-supports a new reset register
-supports 4 tamper detection functions instead of 1
-has no nvmem (like the PCF2129)
-has two output interrupt pins instead of one
-has 1/100th seconds capabilities (not supported in this driver)
-pcf2127 has watchdog clock sources: 1/60, 1, 64 and 4096Hz
pcf2131 has watchdog clock sources: 1/64, 1/4, 4 and 64Hz
-watchdog value register cannot be read after being set

Most of the register addresses are very different, although they still
follow the same layout. For example, the time/date and tamper registers
have a different base address, but the offsets are all the same.
Consequently, the source code of the PCF2127 driver can be easily adapted
to support this new device.

Patches 1 to 6 modify the existing pcf2127 driver to make it more generic
and able to support multiple variants, like the PCF2131. This is done
mostly by using offsets instead of absolute hardcoded register addresses.

Patch 7 add actual support for the PCF2131.

Patch 8 configures all interrupt sources to go through the INT A pin.

Patch 9 changes the PWRMNG bits to be the same with the PCF2131 as they
are with the PCF2127/29 (different default values).

Patch 10 allow to confirm PCF2131 device presence by reading the reset
register fixed pattern.

Patch 11 adapt the time/date registers write sequence for PCF2131 (STOP and
CPR bits).

Patch 12 add support for generic watchdog timing configuration.

Patch 13 add a new flag to identify if device has read support for reading
watchdog register value.
Since the watchdog value register cannot be read on the PCF2131 after
being set, it seems that we cannot detect if watchdog timer was
started by bootloader. I am not sure what is the best way to handle
this situation, suggestions are welcomed.

Patch 14 add the dt-bindings for the PCF2131.

I have tested the driver using a PCF2131-ARD evaluation board connected to
an NXP imx8mp evaluation board:
- Time get/set ok;
- Alarms get/set ok
- Timestamp 1 to 4 ok
- IRQ alarm ok
- Watchdog ok
- Also tested successfully with "RTC Driver Test Example" from

I have also tested the driver on a custom PCF2129 adapter board connected to a
beaglebone black.

Thank you.

Link: [v1]
Link: [v2]

Changes for V3:
- Rebased for kernel v6.1

Changes for V2:
- In general, fix and improvements after I have tested on real hardware
- Fix alarm interrupt A/B mask setting for PCF2131:
PCF2131_BIT_INT_AIE must be cleared, not set, to enable interrupt.
- Remove low_reg validation: only check if TS interrupt flag is
defined, as low_reg is defined at address 0 for PCF2127/29.
- Change PWRMNG value for PCF2131: default is different than PCF2127/29.
- Adapt time/date registers write sequence for PCF2131 (STOP and CPR bits).
- Map all interrupt sources to INT A pin
- Read and validate PCF2131 device presence from RESET register
- Adapt watchdog configuration for PCF2131

Hugo Villeneuve (14):
rtc: pcf2127: add variant-specific configuration structure
rtc: pcf2127: adapt for time/date registers at any offset
rtc: pcf2127: adapt for alarm registers at any offset
rtc: pcf2127: adapt for WD registers at any offset
rtc: pcf2127: adapt for CLKOUT register at any offset
rtc: pcf2127: add support for multiple TS functions
rtc: pcf2127: add support for PCF2131 RTC
rtc: pcf2127: add support for PCF2131 interrupts on output INT_A
rtc: pcf2127: set PWRMNG value for PCF2131
rtc: pcf2127: read and validate PCF2131 device signature
rtc: pcf2127: adapt time/date registers write sequence for PCF2131
rtc: pcf2127: support generic watchdog timing configuration
rtc: pcf2127: add flag for watchdog register value read support
dt-bindings: rtc: pcf2127: add PCF2131

.../devicetree/bindings/rtc/nxp,pcf2127.yaml | 4 +-
drivers/rtc/Kconfig | 4 +-
drivers/rtc/rtc-pcf2127.c | 939 ++++++++++++++----
3 files changed, 752 insertions(+), 195 deletions(-)


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