diff mbox

[v3,4/8] rtc: ac100: Add RTC driver for X-Powers AC100

Message ID 1466391138-12862-5-git-send-email-wens@csie.org
State Superseded
Headers show

Commit Message

Chen-Yu Tsai June 20, 2016, 2:52 a.m. UTC 
X-Powers AC100 is a codec / RTC combo chip. This driver supports
the RTC sub-device.

The RTC block also has clock outputs and non-volatile storage.
Non-volatile storage wthin the RTC hardware is not supported.
Clock output support is added in the next patch.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
Changes since v2:

  - Fixed off-by-1 errors in register mask macros
  - Fixed copy-paste error in set_alarm function
  - Drop uie_unsupported, since the alarm works now
  - Fixed up copyright notice
  - Changed license to GPL v2, matching mfd driver

---
 drivers/rtc/Kconfig     |  10 ++
 drivers/rtc/Makefile    |   1 +
 drivers/rtc/rtc-ac100.c | 365 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 376 insertions(+)
 create mode 100644 drivers/rtc/rtc-ac100.c

Comments

Alexandre Belloni June 26, 2016, 12:30 a.m. UTC | #1 
Hi,

A few comments, mostly about style.

On 20/06/2016 at 10:52:14 +0800, Chen-Yu Tsai wrote :
> +struct ac100_rtc_dev {
> +	struct rtc_device *rtc;
> +	struct device *dev;
> +	struct regmap *regmap;
> +	struct mutex mutex;

I don't think that mutex is needed. Instead, you can take rtc->ops_lock
from the interrupt handler.

> +	int irq;
> +	unsigned long alarm;
> +};
> +
> +static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
> +{
> +	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
> +	struct regmap *regmap = chip->regmap;
> +	u16 reg[7];
> +	int ret;
> +
> +	ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
> +	if (ret)
> +		return ret;
> +
> +	rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
> +	rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
> +	rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
> +	rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
> +	rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
> +	rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK);
> +	rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK);
> +
> +	rtc_tm->tm_mon  -= 1;

I would put the - 1 inline with the first tm_mon assignment.

> +
> +	/*
> +	 * switch from (data_year->min)-relative offset to
> +	 * a (1900)-relative one
> +	 */
> +	rtc_tm->tm_year += AC100_YEAR_OFF;

Unless you feel the comment is absolutely necessary, I'd also put that
with the first tm_year assignment.

BTW, is that RTC aware that 0 is actually 1970? And so 2000 (30) is not
a leap year but 2016 is? I'd say that this is not the case, seeing
AC100_RTC_YEA_LEAP but it is worth checking.

Is this bit (AC100_RTC_YEA_LEAP) updated by the rtc? IF that is not the
case, the time will have to be set at least once between first of
January and 28th of February of leap years else it will fail...

> +
> +	return rtc_valid_tm(rtc_tm);
> +}
> +
> +static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
> +{
> +	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
> +	struct regmap *regmap = chip->regmap;
> +	int year;
> +	u16 reg[8];
> +
> +	/* our RTC has a limited year range... */
> +	year = rtc_tm->tm_year + 1900;
> +	if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
> +		dev_err(dev, "rtc only supports year in range %d - %d\n",
> +			AC100_YEAR_MIN, AC100_YEAR_MAX);
> +		return -EINVAL;
> +	}
> +

What about:

year = rtc_tm->tm_year - AC100_YEAR_OFF
if (year < 0 || year > (AC100_YEAR_MAX - 1900))

It allows to reuse year for the reg[6] assignment. IT is a simple
suggestion, maybe the compiler is smarter than I am ;).

> +	/* correct offsets */
> +	rtc_tm->tm_year -= AC100_YEAR_OFF;
> +	rtc_tm->tm_mon += 1;
> +

Those could also got inline with their respective reg[] assignment


> +	/* convert to BCD */
> +	reg[0] = bin2bcd(rtc_tm->tm_sec)  & AC100_RTC_SEC_MASK;
> +	reg[1] = bin2bcd(rtc_tm->tm_min)  & AC100_RTC_MIN_MASK;
> +	reg[2] = bin2bcd(rtc_tm->tm_hour) & AC100_RTC_HOU_MASK;
> +	reg[3] = bin2bcd(rtc_tm->tm_wday) & AC100_RTC_WEE_MASK;
> +	reg[4] = bin2bcd(rtc_tm->tm_mday) & AC100_RTC_DAY_MASK;
> +	reg[5] = bin2bcd(rtc_tm->tm_mon)  & AC100_RTC_MON_MASK;
> +	reg[6] = bin2bcd(rtc_tm->tm_year) & AC100_RTC_YEA_MASK;
> +	/* trigger write */
> +	reg[7] = AC100_RTC_UPD_TRIGGER;
> +
> +	/* Is it a leap year? */
> +	if (is_leap_year(year))
> +		reg[6] |= AC100_RTC_YEA_LEAP;
> +
> +	return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
> +}
> +
> +

[...]

> +	alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
> +	alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
> +	alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
> +	alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
> +	alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
> +	alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK);
> +	alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK);
> +
> +	alrm_tm->tm_mon  -= 1;
> +
> +	/*
> +	 * switch from (data_year->min)-relative offset to
> +	 * a (1900)-relative one
> +	 */
> +	alrm_tm->tm_year += AC100_YEAR_OFF;
> +

Well, same comments as in ac100_rtc_get_time()


> +out:
> +	mutex_unlock(&chip->mutex);
> +	return ret;
> +}
> +
> +static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
> +{
> +	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
> +	struct regmap *regmap = chip->regmap;
> +	struct rtc_time *alrm_tm = &alrm->time;
> +	u16 reg[8];
> +	int year;
> +	int ret;
> +
> +	/* our alarm has a limited year range... */
> +	year = alrm_tm->tm_year + 1900;
> +	if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
> +		dev_err(dev, "alarm only supports year in range %d - %d\n",
> +			AC100_YEAR_MIN, AC100_YEAR_MAX);
> +		return -EINVAL;
> +	}
> +
> +	/* correct offsets */
> +	alrm_tm->tm_year -= AC100_YEAR_OFF;
> +	alrm_tm->tm_mon += 1;
> +

Same comment as ac100_rtc_set_time()

> +	/* convert to BCD */
> +	reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	/* Do not enable weekday alarm */
> +	reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
> +	reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	reg[5] = (bin2bcd(alrm_tm->tm_mon)  & AC100_ALM_MON_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	reg[6] = (bin2bcd(alrm_tm->tm_year) & AC100_ALM_YEA_MASK) |
> +			AC100_ALM_ENABLE_FLAG;
> +	/* trigger write */
> +	reg[7] = AC100_ALM_UPD_TRIGGER;
> +
> +	mutex_lock(&chip->mutex);
> +
> +	ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
> +	if (ret)
> +		goto out;
> +
> +	ret = _ac100_rtc_alarm_irq_enable(chip, alrm->enabled);
> +
> +out:
> +	mutex_unlock(&chip->mutex);
> +	return ret;
> +}
> +
Alexandre Belloni June 26, 2016, 1:02 a.m. UTC | #2 
On 20/06/2016 at 10:52:14 +0800, Chen-Yu Tsai wrote :
> +static int ac100_rtc_probe(struct platform_device *pdev)
> +{
> +	struct ac100_dev *ac100 = dev_get_drvdata(pdev->dev.parent);
> +	struct ac100_rtc_dev *chip;
> +	int ret;
> +
> +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> +	platform_set_drvdata(pdev, chip);
> +	chip->dev = &pdev->dev;
> +	chip->regmap = ac100->regmap;
> +	mutex_init(&chip->mutex);
> +
> +	chip->irq = of_irq_get(pdev->dev.of_node, 0);

Forgot that one, platform_get_irq() is probably more common but I don't
care that much. I think you can then avoid including of.h and of_irq.h.

> +	if (chip->irq < 0) {
> +		dev_err(&pdev->dev, "No IRQ resource\n");
> +		return chip->irq;
> +	}
> +
Chen-Yu Tsai June 26, 2016, 2:54 p.m. UTC | #3 
On Sun, Jun 26, 2016 at 8:30 AM, Alexandre Belloni
<alexandre.belloni@free-electrons.com> wrote:
> Hi,
>
> A few comments, mostly about style.
>
> On 20/06/2016 at 10:52:14 +0800, Chen-Yu Tsai wrote :
>> +struct ac100_rtc_dev {
>> +     struct rtc_device *rtc;
>> +     struct device *dev;
>> +     struct regmap *regmap;
>> +     struct mutex mutex;
>
> I don't think that mutex is needed. Instead, you can take rtc->ops_lock
> from the interrupt handler.

OK. I didn't think using the lock from the rtc device was a good idea.

>
>> +     int irq;
>> +     unsigned long alarm;
>> +};
>> +
>> +static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
>> +{
>> +     struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
>> +     struct regmap *regmap = chip->regmap;
>> +     u16 reg[7];
>> +     int ret;
>> +
>> +     ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
>> +     if (ret)
>> +             return ret;
>> +
>> +     rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
>> +     rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
>> +     rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
>> +     rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
>> +     rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
>> +     rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK);
>> +     rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK);
>> +
>> +     rtc_tm->tm_mon  -= 1;
>
> I would put the - 1 inline with the first tm_mon assignment.

OK

>
>> +
>> +     /*
>> +      * switch from (data_year->min)-relative offset to
>> +      * a (1900)-relative one
>> +      */
>> +     rtc_tm->tm_year += AC100_YEAR_OFF;
>
> Unless you feel the comment is absolutely necessary, I'd also put that
> with the first tm_year assignment.
>
> BTW, is that RTC aware that 0 is actually 1970? And so 2000 (30) is not
> a leap year but 2016 is? I'd say that this is not the case, seeing
> AC100_RTC_YEA_LEAP but it is worth checking.
>
> Is this bit (AC100_RTC_YEA_LEAP) updated by the rtc? IF that is not the
> case, the time will have to be set at least once between first of
> January and 28th of February of leap years else it will fail...

Unfortunately it is not. The datasheet explicitly said the RTC does not
update the leap year bit. So yes, the RTC will have to be updated at
least once a year...

>> +
>> +     return rtc_valid_tm(rtc_tm);
>> +}
>> +
>> +static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
>> +{
>> +     struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
>> +     struct regmap *regmap = chip->regmap;
>> +     int year;
>> +     u16 reg[8];
>> +
>> +     /* our RTC has a limited year range... */
>> +     year = rtc_tm->tm_year + 1900;
>> +     if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
>> +             dev_err(dev, "rtc only supports year in range %d - %d\n",
>> +                     AC100_YEAR_MIN, AC100_YEAR_MAX);
>> +             return -EINVAL;
>> +     }
>> +
>
> What about:
>
> year = rtc_tm->tm_year - AC100_YEAR_OFF
> if (year < 0 || year > (AC100_YEAR_MAX - 1900))
>
> It allows to reuse year for the reg[6] assignment. IT is a simple
> suggestion, maybe the compiler is smarter than I am ;).
>
>> +     /* correct offsets */
>> +     rtc_tm->tm_year -= AC100_YEAR_OFF;
>> +     rtc_tm->tm_mon += 1;
>> +
>
> Those could also got inline with their respective reg[] assignment

OK. I'll see if I can still fit everything in a single line, to keep
the nice table-like formatting.

>
>
>> +     /* convert to BCD */
>> +     reg[0] = bin2bcd(rtc_tm->tm_sec)  & AC100_RTC_SEC_MASK;
>> +     reg[1] = bin2bcd(rtc_tm->tm_min)  & AC100_RTC_MIN_MASK;
>> +     reg[2] = bin2bcd(rtc_tm->tm_hour) & AC100_RTC_HOU_MASK;
>> +     reg[3] = bin2bcd(rtc_tm->tm_wday) & AC100_RTC_WEE_MASK;
>> +     reg[4] = bin2bcd(rtc_tm->tm_mday) & AC100_RTC_DAY_MASK;
>> +     reg[5] = bin2bcd(rtc_tm->tm_mon)  & AC100_RTC_MON_MASK;
>> +     reg[6] = bin2bcd(rtc_tm->tm_year) & AC100_RTC_YEA_MASK;
>> +     /* trigger write */
>> +     reg[7] = AC100_RTC_UPD_TRIGGER;
>> +
>> +     /* Is it a leap year? */
>> +     if (is_leap_year(year))
>> +             reg[6] |= AC100_RTC_YEA_LEAP;
>> +
>> +     return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
>> +}
>> +
>> +
>
> [...]
>
>> +     alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
>> +     alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
>> +     alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
>> +     alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
>> +     alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
>> +     alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK);
>> +     alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK);
>> +
>> +     alrm_tm->tm_mon  -= 1;
>> +
>> +     /*
>> +      * switch from (data_year->min)-relative offset to
>> +      * a (1900)-relative one
>> +      */
>> +     alrm_tm->tm_year += AC100_YEAR_OFF;
>> +
>
> Well, same comments as in ac100_rtc_get_time()
>
>
>> +out:
>> +     mutex_unlock(&chip->mutex);
>> +     return ret;
>> +}
>> +
>> +static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
>> +{
>> +     struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
>> +     struct regmap *regmap = chip->regmap;
>> +     struct rtc_time *alrm_tm = &alrm->time;
>> +     u16 reg[8];
>> +     int year;
>> +     int ret;
>> +
>> +     /* our alarm has a limited year range... */
>> +     year = alrm_tm->tm_year + 1900;
>> +     if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
>> +             dev_err(dev, "alarm only supports year in range %d - %d\n",
>> +                     AC100_YEAR_MIN, AC100_YEAR_MAX);
>> +             return -EINVAL;
>> +     }
>> +
>> +     /* correct offsets */
>> +     alrm_tm->tm_year -= AC100_YEAR_OFF;
>> +     alrm_tm->tm_mon += 1;
>> +
>
> Same comment as ac100_rtc_set_time()
>
>> +     /* convert to BCD */
>> +     reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     /* Do not enable weekday alarm */
>> +     reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
>> +     reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     reg[5] = (bin2bcd(alrm_tm->tm_mon)  & AC100_ALM_MON_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     reg[6] = (bin2bcd(alrm_tm->tm_year) & AC100_ALM_YEA_MASK) |
>> +                     AC100_ALM_ENABLE_FLAG;
>> +     /* trigger write */
>> +     reg[7] = AC100_ALM_UPD_TRIGGER;
>> +
>> +     mutex_lock(&chip->mutex);
>> +
>> +     ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
>> +     if (ret)
>> +             goto out;
>> +
>> +     ret = _ac100_rtc_alarm_irq_enable(chip, alrm->enabled);
>> +
>> +out:
>> +     mutex_unlock(&chip->mutex);
>> +     return ret;
>> +}
>> +

Thanks for the review!

ChenYu
diff mbox

Patch

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 18639e0cb6e2..b9d7cbb6bd76 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -183,6 +183,16 @@  config RTC_DRV_ABX80X
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-abx80x.
 
+config RTC_DRV_AC100
+	tristate "X-Powers AC100"
+	depends on MFD_AC100
+	help
+	  If you say yes here you get support for the real-time clock found
+	  in X-Powers AC100 family peripheral ICs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-ac100.
+
 config RTC_DRV_AS3722
 	tristate "ams AS3722 RTC driver"
 	depends on MFD_AS3722
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index ea2833723fa9..b07c28779573 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -26,6 +26,7 @@  obj-$(CONFIG_RTC_DRV_AB3100)	+= rtc-ab3100.o
 obj-$(CONFIG_RTC_DRV_AB8500)	+= rtc-ab8500.o
 obj-$(CONFIG_RTC_DRV_ABB5ZES3)	+= rtc-ab-b5ze-s3.o
 obj-$(CONFIG_RTC_DRV_ABX80X)	+= rtc-abx80x.o
+obj-$(CONFIG_RTC_DRV_AC100)	+= rtc-ac100.o
 obj-$(CONFIG_RTC_DRV_ARMADA38X)	+= rtc-armada38x.o
 obj-$(CONFIG_RTC_DRV_AS3722)	+= rtc-as3722.o
 obj-$(CONFIG_RTC_DRV_ASM9260)	+= rtc-asm9260.o
diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
new file mode 100644
index 000000000000..752bc0771d71
--- /dev/null
+++ b/drivers/rtc/rtc-ac100.c
@@ -0,0 +1,365 @@ 
+/*
+ * RTC Driver for X-Powers AC100
+ *
+ * Copyright (c) 2016 Chen-Yu Tsai
+ *
+ * Chen-Yu Tsai <wens@csie.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/bcd.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/ac100.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+
+/* Control register */
+#define AC100_RTC_CTRL_24HOUR	BIT(0)
+
+/* RTC */
+#define AC100_RTC_SEC_MASK	GENMASK(6, 0)
+#define AC100_RTC_MIN_MASK	GENMASK(6, 0)
+#define AC100_RTC_HOU_MASK	GENMASK(5, 0)
+#define AC100_RTC_WEE_MASK	GENMASK(2, 0)
+#define AC100_RTC_DAY_MASK	GENMASK(5, 0)
+#define AC100_RTC_MON_MASK	GENMASK(4, 0)
+#define AC100_RTC_YEA_MASK	GENMASK(7, 0)
+#define AC100_RTC_YEA_LEAP	BIT(15)
+#define AC100_RTC_UPD_TRIGGER	BIT(15)
+
+/* Alarm (wall clock) */
+#define AC100_ALM_INT_ENABLE	BIT(0)
+
+#define AC100_ALM_SEC_MASK	GENMASK(6, 0)
+#define AC100_ALM_MIN_MASK	GENMASK(6, 0)
+#define AC100_ALM_HOU_MASK	GENMASK(5, 0)
+#define AC100_ALM_WEE_MASK	GENMASK(2, 0)
+#define AC100_ALM_DAY_MASK	GENMASK(5, 0)
+#define AC100_ALM_MON_MASK	GENMASK(4, 0)
+#define AC100_ALM_YEA_MASK	GENMASK(7, 0)
+#define AC100_ALM_ENABLE_FLAG	BIT(15)
+#define AC100_ALM_UPD_TRIGGER	BIT(15)
+
+/*
+ * The year parameter passed to the driver is usually an offset relative to
+ * the year 1900. This macro is used to convert this offset to another one
+ * relative to the minimum year allowed by the hardware.
+ *
+ * The year range is 1970 - 2069. This range is selected to match Allwinner's
+ * driver.
+ */
+#define AC100_YEAR_MIN				1970
+#define AC100_YEAR_MAX				2069
+#define AC100_YEAR_OFF				(AC100_YEAR_MIN - 1900)
+
+struct ac100_rtc_dev {
+	struct rtc_device *rtc;
+	struct device *dev;
+	struct regmap *regmap;
+	struct mutex mutex;
+	int irq;
+	unsigned long alarm;
+};
+
+static int ac100_rtc_get_time(struct device *dev, struct rtc_time *rtc_tm)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	struct regmap *regmap = chip->regmap;
+	u16 reg[7];
+	int ret;
+
+	ret = regmap_bulk_read(regmap, AC100_RTC_SEC, reg, 7);
+	if (ret)
+		return ret;
+
+	rtc_tm->tm_sec  = bcd2bin(reg[0] & AC100_RTC_SEC_MASK);
+	rtc_tm->tm_min  = bcd2bin(reg[1] & AC100_RTC_MIN_MASK);
+	rtc_tm->tm_hour = bcd2bin(reg[2] & AC100_RTC_HOU_MASK);
+	rtc_tm->tm_wday = bcd2bin(reg[3] & AC100_RTC_WEE_MASK);
+	rtc_tm->tm_mday = bcd2bin(reg[4] & AC100_RTC_DAY_MASK);
+	rtc_tm->tm_mon  = bcd2bin(reg[5] & AC100_RTC_MON_MASK);
+	rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK);
+
+	rtc_tm->tm_mon  -= 1;
+
+	/*
+	 * switch from (data_year->min)-relative offset to
+	 * a (1900)-relative one
+	 */
+	rtc_tm->tm_year += AC100_YEAR_OFF;
+
+	return rtc_valid_tm(rtc_tm);
+}
+
+static int ac100_rtc_set_time(struct device *dev, struct rtc_time *rtc_tm)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	struct regmap *regmap = chip->regmap;
+	int year;
+	u16 reg[8];
+
+	/* our RTC has a limited year range... */
+	year = rtc_tm->tm_year + 1900;
+	if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
+		dev_err(dev, "rtc only supports year in range %d - %d\n",
+			AC100_YEAR_MIN, AC100_YEAR_MAX);
+		return -EINVAL;
+	}
+
+	/* correct offsets */
+	rtc_tm->tm_year -= AC100_YEAR_OFF;
+	rtc_tm->tm_mon += 1;
+
+	/* convert to BCD */
+	reg[0] = bin2bcd(rtc_tm->tm_sec)  & AC100_RTC_SEC_MASK;
+	reg[1] = bin2bcd(rtc_tm->tm_min)  & AC100_RTC_MIN_MASK;
+	reg[2] = bin2bcd(rtc_tm->tm_hour) & AC100_RTC_HOU_MASK;
+	reg[3] = bin2bcd(rtc_tm->tm_wday) & AC100_RTC_WEE_MASK;
+	reg[4] = bin2bcd(rtc_tm->tm_mday) & AC100_RTC_DAY_MASK;
+	reg[5] = bin2bcd(rtc_tm->tm_mon)  & AC100_RTC_MON_MASK;
+	reg[6] = bin2bcd(rtc_tm->tm_year) & AC100_RTC_YEA_MASK;
+	/* trigger write */
+	reg[7] = AC100_RTC_UPD_TRIGGER;
+
+	/* Is it a leap year? */
+	if (is_leap_year(year))
+		reg[6] |= AC100_RTC_YEA_LEAP;
+
+	return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
+}
+
+static int _ac100_rtc_alarm_irq_enable(struct ac100_rtc_dev *chip,
+				       unsigned int en)
+{
+	struct regmap *regmap = chip->regmap;
+	unsigned int val;
+
+	val = en ? AC100_ALM_INT_ENABLE : 0;
+
+	return regmap_write(regmap, AC100_ALM_INT_ENA, val);
+}
+
+static int ac100_rtc_alarm_irq_enable(struct device *dev, unsigned int en)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&chip->mutex);
+	ret = _ac100_rtc_alarm_irq_enable(chip, en);
+	mutex_unlock(&chip->mutex);
+
+	return ret;
+}
+
+static int ac100_rtc_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	struct regmap *regmap = chip->regmap;
+	struct rtc_time *alrm_tm = &alrm->time;
+	u16 reg[7];
+	unsigned int val;
+	int ret;
+
+	mutex_lock(&chip->mutex);
+
+	ret = regmap_read(regmap, AC100_ALM_INT_ENA, &val);
+	if (ret)
+		goto out;
+
+	alrm->enabled = !!(val & AC100_ALM_INT_ENABLE);
+
+	ret = regmap_bulk_read(regmap, AC100_ALM_SEC, reg, 7);
+	if (ret)
+		goto out;
+
+	alrm_tm->tm_sec  = bcd2bin(reg[0] & AC100_ALM_SEC_MASK);
+	alrm_tm->tm_min  = bcd2bin(reg[1] & AC100_ALM_MIN_MASK);
+	alrm_tm->tm_hour = bcd2bin(reg[2] & AC100_ALM_HOU_MASK);
+	alrm_tm->tm_wday = bcd2bin(reg[3] & AC100_ALM_WEE_MASK);
+	alrm_tm->tm_mday = bcd2bin(reg[4] & AC100_ALM_DAY_MASK);
+	alrm_tm->tm_mon  = bcd2bin(reg[5] & AC100_ALM_MON_MASK);
+	alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK);
+
+	alrm_tm->tm_mon  -= 1;
+
+	/*
+	 * switch from (data_year->min)-relative offset to
+	 * a (1900)-relative one
+	 */
+	alrm_tm->tm_year += AC100_YEAR_OFF;
+
+out:
+	mutex_unlock(&chip->mutex);
+	return ret;
+}
+
+static int ac100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	struct regmap *regmap = chip->regmap;
+	struct rtc_time *alrm_tm = &alrm->time;
+	u16 reg[8];
+	int year;
+	int ret;
+
+	/* our alarm has a limited year range... */
+	year = alrm_tm->tm_year + 1900;
+	if (year < AC100_YEAR_MIN || year > AC100_YEAR_MAX) {
+		dev_err(dev, "alarm only supports year in range %d - %d\n",
+			AC100_YEAR_MIN, AC100_YEAR_MAX);
+		return -EINVAL;
+	}
+
+	/* correct offsets */
+	alrm_tm->tm_year -= AC100_YEAR_OFF;
+	alrm_tm->tm_mon += 1;
+
+	/* convert to BCD */
+	reg[0] = (bin2bcd(alrm_tm->tm_sec)  & AC100_ALM_SEC_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	reg[1] = (bin2bcd(alrm_tm->tm_min)  & AC100_ALM_MIN_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	reg[2] = (bin2bcd(alrm_tm->tm_hour) & AC100_ALM_HOU_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	/* Do not enable weekday alarm */
+	reg[3] = bin2bcd(alrm_tm->tm_wday) & AC100_ALM_WEE_MASK;
+	reg[4] = (bin2bcd(alrm_tm->tm_mday) & AC100_ALM_DAY_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	reg[5] = (bin2bcd(alrm_tm->tm_mon)  & AC100_ALM_MON_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	reg[6] = (bin2bcd(alrm_tm->tm_year) & AC100_ALM_YEA_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	/* trigger write */
+	reg[7] = AC100_ALM_UPD_TRIGGER;
+
+	mutex_lock(&chip->mutex);
+
+	ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
+	if (ret)
+		goto out;
+
+	ret = _ac100_rtc_alarm_irq_enable(chip, alrm->enabled);
+
+out:
+	mutex_unlock(&chip->mutex);
+	return ret;
+}
+
+static irqreturn_t ac100_rtc_irq(int irq, void *data)
+{
+	struct ac100_rtc_dev *chip = data;
+	struct regmap *regmap = chip->regmap;
+	unsigned int val = 0;
+	int ret;
+
+	mutex_lock(&chip->mutex);
+
+	/* read status */
+	ret = regmap_read(regmap, AC100_ALM_INT_STA, &val);
+	if (ret)
+		goto out;
+
+	if (val & AC100_ALM_INT_ENABLE) {
+		/* signal rtc framework */
+		rtc_update_irq(chip->rtc, 1, RTC_AF | RTC_IRQF);
+
+		/* clear status */
+		ret = regmap_write(regmap, AC100_ALM_INT_STA, val);
+		if (ret)
+			goto out;
+
+		/* disable interrupt */
+		ret = _ac100_rtc_alarm_irq_enable(chip, 0);
+		if (ret)
+			goto out;
+	}
+
+out:
+	mutex_unlock(&chip->mutex);
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops ac100_rtc_ops = {
+	.read_time	  = ac100_rtc_get_time,
+	.set_time	  = ac100_rtc_set_time,
+	.read_alarm	  = ac100_rtc_get_alarm,
+	.set_alarm	  = ac100_rtc_set_alarm,
+	.alarm_irq_enable = ac100_rtc_alarm_irq_enable,
+};
+
+static int ac100_rtc_probe(struct platform_device *pdev)
+{
+	struct ac100_dev *ac100 = dev_get_drvdata(pdev->dev.parent);
+	struct ac100_rtc_dev *chip;
+	int ret;
+
+	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
+	platform_set_drvdata(pdev, chip);
+	chip->dev = &pdev->dev;
+	chip->regmap = ac100->regmap;
+	mutex_init(&chip->mutex);
+
+	chip->irq = of_irq_get(pdev->dev.of_node, 0);
+	if (chip->irq < 0) {
+		dev_err(&pdev->dev, "No IRQ resource\n");
+		return chip->irq;
+	}
+
+	ret = devm_request_threaded_irq(&pdev->dev, chip->irq, NULL,
+					ac100_rtc_irq,
+					IRQF_SHARED | IRQF_ONESHOT,
+					dev_name(&pdev->dev), chip);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not request IRQ\n");
+		return ret;
+	}
+
+	/* always use 24 hour mode */
+	regmap_write_bits(chip->regmap, AC100_RTC_CTRL, AC100_RTC_CTRL_24HOUR,
+			  AC100_RTC_CTRL_24HOUR);
+
+	/* disable counter alarm interrupt */
+	regmap_write(chip->regmap, AC100_ALM_INT_ENA, 0);
+
+	/* clear counter alarm pending interrupts */
+	regmap_write(chip->regmap, AC100_ALM_INT_STA, AC100_ALM_INT_ENABLE);
+
+	chip->rtc = devm_rtc_device_register(&pdev->dev, "rtc-ac100",
+					     &ac100_rtc_ops, THIS_MODULE);
+	if (IS_ERR(chip->rtc)) {
+		dev_err(&pdev->dev, "unable to register device\n");
+		return PTR_ERR(chip->rtc);
+	}
+
+	dev_info(&pdev->dev, "RTC enabled\n");
+
+	return 0;
+}
+
+static struct platform_driver ac100_rtc_driver = {
+	.probe		= ac100_rtc_probe,
+	.driver		= {
+		.name		= "ac100-rtc",
+	},
+};
+module_platform_driver(ac100_rtc_driver);
+
+MODULE_DESCRIPTION("X-Powers AC100 RTC driver");
+MODULE_AUTHOR("Chen-Yu Tsai <wens@csie.org>");
+MODULE_LICENSE("GPL v2");