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    SubjectRe: [PATCH 1/3] mfd: ds1374: Introduce Dallas/Maxim DS1374 MFD core driver
    On 22/06/2020 07:26:56-0700, Guenter Roeck wrote:
    > On Mon, Jun 22, 2020 at 12:14:13PM +0100, Lee Jones wrote:
    > > On Mon, 22 Jun 2020, Johnson CH Chen (陳昭勳) wrote:
    > >
    > > > Dallas/Maxim DS1374 is a counter designed to continuously count
    > > > time in seconds. It provides an I2C interface to the host to
    > > > access RTC clock or Alarm/Watchdog timer.
    > > >
    > > > Add MFD Core driver, supporting the I2C communication to RTC and
    > > > Watchdog devices.
    > > >
    > > > Signed-off-by: Johnson Chen <johnsonch.chen@moxa.com>
    > > > ---
    > > > drivers/mfd/Kconfig | 11 +++++
    > > > drivers/mfd/Makefile | 2 +
    > > > drivers/mfd/ds1374.c | 101 +++++++++++++++++++++++++++++++++++++++++++
    > > > 3 files changed, 114 insertions(+)
    > > > create mode 100644 drivers/mfd/ds1374.c
    > >
    > > Not sure I see the point of this driver.
    > >
    >
    > Not entirely sure either. Seems to me the idea is to use the watchdog
    > subsystem for watchdog functionality, but that is just a guess and not
    > really necessary (the conversion could be done in the rtc driver).
    > I don't think the code as written works - the rtc code uses a mutex
    > which the watchdog driver obviously isn't aware of. The mutex would
    > have to be moved into the mfd code, with respective access functions.
    >
    > Overall this adds a lot of complexity, and it seems the interdependencies
    > between rtc and watchdog functionality are not well understood. Plus,
    > other watchdog drivers have recently been added to other rtc clock chips,
    > so this adds some inconsistencies in the rtc subsystem. Are we going
    > to see this change for all those combined rtc/watchdog drivers ?
    > If so, it might make sense to communicate that now to ensure consistency.
    >

    I read the datasheet again and I agree the watchdog part can live in the
    rtc driver. As only the RTC alarm and the watchdog are mutually
    exclusive. I don't think an MFD driver is necessary. Converting the
    current driver to the watchdog subsystem seems to be the correct way
    forward.

    --
    Alexandre Belloni, Bootlin
    Embedded Linux and Kernel engineering
    https://bootlin.com

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