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    SubjectRe: [PATCH v4 4/9] platform/chrome: rtc: Add RTC driver
    On 23/01/2019 11:33:20-0700, Nick Crews wrote:
    > From: Duncan Laurie <dlaurie@google.com>
    >
    > This Embedded Controller has an internal RTC that is exposed
    > as a standard RTC class driver with read/write functionality.
    >
    > The driver is added to the drivers/rtc/ so that the maintainer of that
    > directory will be able to comment on this change, as that maintainer is
    > the expert on this system. In addition, the driver code is called
    > indirectly after a corresponding device is registered from core.c,
    > as opposed to core.c registering the driver callbacks directly.
    >
    > > hwclock --show --rtc /dev/rtc1
    > 2007-12-31 16:01:20.460959-08:00
    > > hwclock --systohc --rtc /dev/rtc1
    > > hwclock --show --rtc /dev/rtc1
    > 2018-11-29 17:08:00.780793-08:00
    >
    > Signed-off-by: Duncan Laurie <dlaurie@google.com>
    > Acked-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    > Signed-off-by: Nick Crews <ncrews@chromium.org>
    Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

    > ---
    >
    > Changes in v4:
    > - Change me email to @chromium.org from @google.com
    > - Move "Add RTC driver" before "Add sysfs attributes" so that
    > it could get accepted earlier, since it is less contentious
    >
    > Changes in v3:
    > - rm #define for driver name
    > - Don't compute weekday when reading from RTC.
    > Still set weekday when writing, as RTC needs this
    > to control advanced power scheduling
    > - rm check for invalid month data
    > - Set range_min and range_max on rtc_device
    >
    > Changes in v2:
    > - rm license boiler plate
    > - rm "wilco_ec_rtc -" prefix in docstring
    > - Make rtc driver its own module within the drivers/rtc/ directory
    > - Register a rtc device from core.c that is picked up by this driver
    >
    > drivers/platform/chrome/wilco_ec/core.c | 14 ++
    > drivers/rtc/Kconfig | 11 ++
    > drivers/rtc/Makefile | 1 +
    > drivers/rtc/rtc-wilco-ec.c | 177 ++++++++++++++++++++++++
    > 4 files changed, 203 insertions(+)
    > create mode 100644 drivers/rtc/rtc-wilco-ec.c
    >
    > diff --git a/drivers/platform/chrome/wilco_ec/core.c b/drivers/platform/chrome/wilco_ec/core.c
    > index e036d88b6dd8..7cfb047e2c89 100644
    > --- a/drivers/platform/chrome/wilco_ec/core.c
    > +++ b/drivers/platform/chrome/wilco_ec/core.c
    > @@ -87,6 +87,20 @@ static int wilco_ec_probe(struct platform_device *pdev)
    > goto destroy_mec;
    > }
    >
    > + /*
    > + * Register a RTC platform device that will get picked up by the RTC
    > + * subsystem. This platform device will get freed when its parent device
    > + * dev is unregistered.
    > + */
    > + child_pdev = platform_device_register_data(dev, "rtc-wilco-ec",
    > + PLATFORM_DEVID_AUTO,
    > + NULL, 0);
    > + if (IS_ERR(child_pdev)) {
    > + dev_err(dev, "Failed to create RTC platform device\n");
    > + ret = PTR_ERR(child_pdev);
    > + goto destroy_mec;
    > + }
    > +
    > return 0;
    >
    > destroy_mec:
    > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
    > index 225b0b8516f3..d5063c791515 100644
    > --- a/drivers/rtc/Kconfig
    > +++ b/drivers/rtc/Kconfig
    > @@ -1814,4 +1814,15 @@ config RTC_DRV_GOLDFISH
    > Goldfish is a code name for the virtual platform developed by Google
    > for Android emulation.
    >
    > +config RTC_DRV_WILCO_EC
    > + tristate "Wilco EC RTC"
    > + depends on WILCO_EC
    > + default m
    > + help
    > + If you say yes here, you get read/write support for the Real Time
    > + Clock on the Wilco Embedded Controller (Wilco is a kind of Chromebook)
    > +
    > + This can also be built as a module. If so, the module will
    > + be named "rtc_wilco_ec".
    > +
    > endif # RTC_CLASS
    > diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
    > index df022d820bee..6255ea78da25 100644
    > --- a/drivers/rtc/Makefile
    > +++ b/drivers/rtc/Makefile
    > @@ -172,6 +172,7 @@ obj-$(CONFIG_RTC_DRV_V3020) += rtc-v3020.o
    > obj-$(CONFIG_RTC_DRV_VR41XX) += rtc-vr41xx.o
    > obj-$(CONFIG_RTC_DRV_VRTC) += rtc-mrst.o
    > obj-$(CONFIG_RTC_DRV_VT8500) += rtc-vt8500.o
    > +obj-$(CONFIG_RTC_DRV_WILCO_EC) += rtc-wilco-ec.o
    > obj-$(CONFIG_RTC_DRV_WM831X) += rtc-wm831x.o
    > obj-$(CONFIG_RTC_DRV_WM8350) += rtc-wm8350.o
    > obj-$(CONFIG_RTC_DRV_X1205) += rtc-x1205.o
    > diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
    > new file mode 100644
    > index 000000000000..35cc56114c1c
    > --- /dev/null
    > +++ b/drivers/rtc/rtc-wilco-ec.c
    > @@ -0,0 +1,177 @@
    > +// SPDX-License-Identifier: GPL-2.0
    > +/*
    > + * RTC interface for Wilco Embedded Controller with R/W abilities
    > + *
    > + * Copyright 2018 Google LLC
    > + *
    > + * The corresponding platform device is typically registered in
    > + * drivers/platform/chrome/wilco_ec/core.c
    > + */
    > +
    > +#include <linux/bcd.h>
    > +#include <linux/err.h>
    > +#include <linux/kernel.h>
    > +#include <linux/module.h>
    > +#include <linux/platform_device.h>
    > +#include <linux/platform_data/wilco-ec.h>
    > +#include <linux/rtc.h>
    > +#include <linux/timekeeping.h>
    > +
    > +#define EC_COMMAND_CMOS 0x7c
    > +#define EC_CMOS_TOD_WRITE 0x02
    > +#define EC_CMOS_TOD_READ 0x08
    > +
    > +/**
    > + * struct ec_rtc_read - Format of RTC returned by EC.
    > + * @second: Second value (0..59)
    > + * @minute: Minute value (0..59)
    > + * @hour: Hour value (0..23)
    > + * @day: Day value (1..31)
    > + * @month: Month value (1..12)
    > + * @year: Year value (full year % 100)
    > + * @century: Century value (full year / 100)
    > + *
    > + * All values are presented in binary (not BCD).
    > + */
    > +struct ec_rtc_read {
    > + u8 second;
    > + u8 minute;
    > + u8 hour;
    > + u8 day;
    > + u8 month;
    > + u8 year;
    > + u8 century;
    > +} __packed;
    > +
    > +/**
    > + * struct ec_rtc_write - Format of RTC sent to the EC.
    > + * @param: EC_CMOS_TOD_WRITE
    > + * @century: Century value (full year / 100)
    > + * @year: Year value (full year % 100)
    > + * @month: Month value (1..12)
    > + * @day: Day value (1..31)
    > + * @hour: Hour value (0..23)
    > + * @minute: Minute value (0..59)
    > + * @second: Second value (0..59)
    > + * @weekday: Day of the week (0=Saturday)
    > + *
    > + * All values are presented in BCD.
    > + */
    > +struct ec_rtc_write {
    > + u8 param;
    > + u8 century;
    > + u8 year;
    > + u8 month;
    > + u8 day;
    > + u8 hour;
    > + u8 minute;
    > + u8 second;
    > + u8 weekday;
    > +} __packed;
    > +
    > +int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
    > +{
    > + struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
    > + u8 param = EC_CMOS_TOD_READ;
    > + struct ec_rtc_read rtc;
    > + struct wilco_ec_message msg = {
    > + .type = WILCO_EC_MSG_LEGACY,
    > + .flags = WILCO_EC_FLAG_RAW_RESPONSE,
    > + .command = EC_COMMAND_CMOS,
    > + .request_data = &param,
    > + .request_size = sizeof(param),
    > + .response_data = &rtc,
    > + .response_size = sizeof(rtc),
    > + };
    > + int ret;
    > +
    > + ret = wilco_ec_mailbox(ec, &msg);
    > + if (ret < 0)
    > + return ret;
    > +
    > + tm->tm_sec = rtc.second;
    > + tm->tm_min = rtc.minute;
    > + tm->tm_hour = rtc.hour;
    > + tm->tm_mday = rtc.day;
    > + tm->tm_mon = rtc.month - 1;
    > + tm->tm_year = rtc.year + (rtc.century * 100) - 1900;
    > + tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
    > +
    > + /* Don't compute day of week, we don't need it. */
    > + tm->tm_wday = -1;
    > +
    > + return 0;
    > +}
    > +
    > +int wilco_ec_rtc_write(struct device *dev, struct rtc_time *tm)
    > +{
    > + struct wilco_ec_device *ec = dev_get_drvdata(dev->parent);
    > + struct ec_rtc_write rtc;
    > + struct wilco_ec_message msg = {
    > + .type = WILCO_EC_MSG_LEGACY,
    > + .flags = WILCO_EC_FLAG_RAW_RESPONSE,
    > + .command = EC_COMMAND_CMOS,
    > + .request_data = &rtc,
    > + .request_size = sizeof(rtc),
    > + };
    > + int year = tm->tm_year + 1900;
    > + /*
    > + * Convert from 0=Sunday to 0=Saturday for the EC
    > + * We DO need to set weekday because the EC controls battery charging
    > + * schedules that depend on the day of the week.
    > + */
    > + int wday = tm->tm_wday == 6 ? 0 : tm->tm_wday + 1;
    > + int ret;
    > +
    > + rtc.param = EC_CMOS_TOD_WRITE;
    > + rtc.century = bin2bcd(year / 100);
    > + rtc.year = bin2bcd(year % 100);
    > + rtc.month = bin2bcd(tm->tm_mon + 1);
    > + rtc.day = bin2bcd(tm->tm_mday);
    > + rtc.hour = bin2bcd(tm->tm_hour);
    > + rtc.minute = bin2bcd(tm->tm_min);
    > + rtc.second = bin2bcd(tm->tm_sec);
    > + rtc.weekday = bin2bcd(wday);
    > +
    > + ret = wilco_ec_mailbox(ec, &msg);
    > + if (ret < 0)
    > + return ret;
    > +
    > + return 0;
    > +}
    > +
    > +static const struct rtc_class_ops wilco_ec_rtc_ops = {
    > + .read_time = wilco_ec_rtc_read,
    > + .set_time = wilco_ec_rtc_write,
    > +};
    > +
    > +static int wilco_ec_rtc_probe(struct platform_device *pdev)
    > +{
    > + struct rtc_device *rtc;
    > +
    > + rtc = devm_rtc_allocate_device(&pdev->dev);
    > + if (IS_ERR(rtc))
    > + return PTR_ERR(rtc);
    > +
    > + rtc->ops = &wilco_ec_rtc_ops;
    > + /* EC only supports this century */
    > + rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
    > + rtc->range_max = RTC_TIMESTAMP_END_2099;
    > + rtc->owner = THIS_MODULE;
    > +
    > + return rtc_register_device(rtc);
    > +}
    > +
    > +static struct platform_driver wilco_ec_rtc_driver = {
    > + .driver = {
    > + .name = "rtc-wilco-ec",
    > + },
    > + .probe = wilco_ec_rtc_probe,
    > +};
    > +
    > +module_platform_driver(wilco_ec_rtc_driver);
    > +
    > +MODULE_ALIAS("platform:rtc-wilco-ec");
    > +MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
    > +MODULE_LICENSE("GPL v2");
    > +MODULE_DESCRIPTION("Wilco EC RTC driver");
    > --
    > 2.20.1.321.g9e740568ce-goog
    >

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

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