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Date:   Tue, 22 Jan 2019 15:55:55 +0100
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Nick Crews <ncrews@...omium.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Guenter Roeck <groeck@...omium.org>,
        Simon Glass <sjg@...omium.org>,
        Daniel Kurtz <djkurtz@...gle.com>, dlaurie@...omium.org,
        Duncan Laurie <dlaurie@...gle.com>, linux-rtc@...r.kernel.org,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Benson Leung <bleung@...omium.org>,
        Nick Crews <ncrews@...gle.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: Re: [PATCH v3 5/9] platform/chrome: rtc: Add RTC driver

Hi Nick,

Missatge de Nick Crews <ncrews@...omium.org> del dia ds., 19 de gen.
2019 a les 1:17:
>
> From: Duncan Laurie <dlaurie@...gle.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@...gle.com>
> Signed-off-by: Nick Crews <ncrews@...omium.org>
> ---
>
> 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 |  17 +++

Acked-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

>  drivers/rtc/Kconfig                     |  11 ++
>  drivers/rtc/Makefile                    |   1 +
>  drivers/rtc/rtc-wilco-ec.c              | 177 ++++++++++++++++++++++++
>  4 files changed, 206 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 9b4a25e63b56..dd8b896b3833 100644
> --- a/drivers/platform/chrome/wilco_ec/core.c
> +++ b/drivers/platform/chrome/wilco_ec/core.c
> @@ -34,6 +34,7 @@ static int wilco_ec_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
>         struct wilco_ec_device *ec;
> +       struct platform_device *child_pdev;
>         int ret;
>
>         ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
> @@ -76,8 +77,24 @@ static int wilco_ec_probe(struct platform_device *pdev)
>                 goto rm_debugfs;
>         }
>
> +       /*
> +        * 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 remove_sysfs;
> +       }
> +
>         return 0;
>
> +remove_sysfs:
> +       wilco_ec_sysfs_remove(ec);
>  rm_debugfs:
>         wilco_ec_debugfs_remove(ec);
>  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..b721cc3f17f0
> --- /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@...gle.com>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Wilco EC RTC driver");
> --
> 2.20.1.321.g9e740568ce-goog
>

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