[PATCH v8 4/4] platform/chrome: rtc: Add RTC driver

From: Nick Crews
Date: Fri Feb 08 2019 - 19:37:38 EST

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.

To test:
> 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

> 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@xxxxxxxxxx>
Acked-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
Acked-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Signed-off-by: Nick Crews <ncrews@xxxxxxxxxxxx>
---

Changes in v8: None
Changes in v7: None
Changes in v6:
- In the core, actually unregister the RTC child platform_device.

Changes in v5: None
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 | 18 +++
drivers/rtc/Kconfig | 11 ++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-wilco-ec.c | 177 ++++++++++++++++++++++++
include/linux/platform_data/wilco-ec.h | 2 +
5 files changed, 209 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 af5fd288b63b..05e1e2be1c91 100644
--- a/drivers/platform/chrome/wilco_ec/core.c
+++ b/drivers/platform/chrome/wilco_ec/core.c
@@ -42,6 +42,7 @@ static int wilco_ec_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct wilco_ec_device *ec;
+ int ret;

ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
if (!ec)
@@ -78,13 +79,30 @@ static int wilco_ec_probe(struct platform_device *pdev)
PLATFORM_DEVID_AUTO,
NULL, 0);

+ /* Register a child device that will be found by the RTC driver. */
+ ec->rtc_pdev = platform_device_register_data(dev, "rtc-wilco-ec",
+ PLATFORM_DEVID_AUTO,
+ NULL, 0);
+ if (IS_ERR(ec->rtc_pdev)) {
+ dev_err(dev, "Failed to create RTC platform device\n");
+ ret = PTR_ERR(ec->rtc_pdev);
+ goto unregister_debugfs;
+ }
+
return 0;
+
+unregister_debugfs:
+ if (ec->debugfs_pdev)
+ platform_device_unregister(ec->debugfs_pdev);
+ cros_ec_lpc_mec_destroy();
+ return ret;
}

static int wilco_ec_remove(struct platform_device *pdev)
{
struct wilco_ec_device *ec = platform_get_drvdata(pdev);

+ platform_device_unregister(ec->rtc_pdev);
if (ec->debugfs_pdev)
platform_device_unregister(ec->debugfs_pdev);

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@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Wilco EC RTC driver");
diff --git a/include/linux/platform_data/wilco-ec.h b/include/linux/platform_data/wilco-ec.h
index 5344975afa1a..446473a46b88 100644
--- a/include/linux/platform_data/wilco-ec.h
+++ b/include/linux/platform_data/wilco-ec.h
@@ -35,6 +35,7 @@
* is used to hold the request and the response.
* @data_size: Size of the data buffer used for EC communication.
* @debugfs_pdev: The child platform_device used by the debugfs sub-driver.
+ * @rtc_pdev: The child platform_device used by the RTC sub-driver.
*/
struct wilco_ec_device {
struct device *dev;
@@ -45,6 +46,7 @@ struct wilco_ec_device {
void *data_buffer;
size_t data_size;
struct platform_device *debugfs_pdev;
+ struct platform_device *rtc_pdev;
};

/**
--
2.20.1.791.gb4d0f1c61a-goog