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Subject: [PATCH 0/2] rtc: pcf8523: Make DSM for battery switch-over configurable from DT and enable it for the cubox-i
Date:   Sun, 19 Jul 2020 15:50:26 +0100
Message-Id: <20200719145028.3370-1-miguelborgesdefreitas@gmail.com>
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From: Miguel Borges de Freitas <miguelborgesdefreitas@gmail.com>

The pcf8523 has two configurable modes for the battery switch-over functionality:
(i) the default mode and (ii) the direct switching mode. For the default mode to work (at the
moment the only driver option), a filtering circuit consisting of a series resistor of 1 kOhm
and a capacitor of 3.3 microF must be added to the VDD pin input to guarantee a voltage drop
of less 0.7V/ms for the oscillator operation reliability (see pp.54 of the datasheet).
Some boards (e.g. the cubox-i) do not include such circuitry and are designed to work only in
direct switching mode. In fact, this is the recommended mode in the datasheet for hw designs
where VDD is always expected to be higher than VBAT.
If DSM is not enabled, after a power cycle, the voltage drop may be too high causing the
oscillator to stop working momentarily and the REG_SECONDS_OS bit to be set.
This causes userspace applications such as timedatectl and hwclock to fail when obtaining
the RTC time (RTC_RD_TIME: Invalid argument).
Hence, this patch set makes DSM configurable for the pcf8523 RTC in the device-tree and enables it
for the board where this issue was detected - the cubox-i. Note that if the RTC comes from an
inconsistent state, the software reset will override any power management options set during the
probe phase. Thus, pm is also enforced in pcf8523_start_rtc.


Miguel Borges de Freitas (2):
  rtc: pcf8523: Make DSM for battery switch-over configurable from DT
  ARM: dts: imx6qdl-cubox-i: enable DSM for the RTC

 Documentation/devicetree/bindings/rtc/nxp,pcf8523.txt |  7 ++++++-
 Documentation/devicetree/bindings/rtc/rtc.yaml        |  7 +++++++
 arch/arm/boot/dts/imx6qdl-cubox-i.dtsi                |  1 +
 drivers/rtc/rtc-pcf8523.c                             | 13 ++++++++++---
 4 files changed, 24 insertions(+), 4 deletions(-)

-- 
1.8.3.1