Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 661 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
new file mode 100644
index 000000000..784b67628
--- /dev/null
+++ b/drivers/rtc/rtc-ac100.c
@@ -0,0 +1,661 @@
+/*
+ * 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/clk-provider.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/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+
+/* Control register */
+#define AC100_RTC_CTRL_24HOUR	BIT(0)
+
+/* Clock output register bits */
+#define AC100_CLKOUT_PRE_DIV_SHIFT	5
+#define AC100_CLKOUT_PRE_DIV_WIDTH	3
+#define AC100_CLKOUT_MUX_SHIFT		4
+#define AC100_CLKOUT_MUX_WIDTH		1
+#define AC100_CLKOUT_DIV_SHIFT		1
+#define AC100_CLKOUT_DIV_WIDTH		3
+#define AC100_CLKOUT_EN			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_clkout {
+	struct clk_hw hw;
+	struct regmap *regmap;
+	u8 offset;
+};
+
+#define to_ac100_clkout(_hw) container_of(_hw, struct ac100_clkout, hw)
+
+#define AC100_RTC_32K_NAME	"ac100-rtc-32k"
+#define AC100_RTC_32K_RATE	32768
+#define AC100_CLKOUT_NUM	3
+
+static const char * const ac100_clkout_names[AC100_CLKOUT_NUM] = {
+	"ac100-cko1-rtc",
+	"ac100-cko2-rtc",
+	"ac100-cko3-rtc",
+};
+
+struct ac100_rtc_dev {
+	struct rtc_device *rtc;
+	struct device *dev;
+	struct regmap *regmap;
+	int irq;
+	unsigned long alarm;
+
+	struct clk_hw *rtc_32k_clk;
+	struct ac100_clkout clks[AC100_CLKOUT_NUM];
+	struct clk_hw_onecell_data *clk_data;
+};
+
+/**
+ * Clock controls for 3 clock output pins
+ */
+
+static const struct clk_div_table ac100_clkout_prediv[] = {
+	{ .val = 0, .div = 1 },
+	{ .val = 1, .div = 2 },
+	{ .val = 2, .div = 4 },
+	{ .val = 3, .div = 8 },
+	{ .val = 4, .div = 16 },
+	{ .val = 5, .div = 32 },
+	{ .val = 6, .div = 64 },
+	{ .val = 7, .div = 122 },
+	{ },
+};
+
+/* Abuse the fact that one parent is 32768 Hz, and the other is 4 MHz */
+static unsigned long ac100_clkout_recalc_rate(struct clk_hw *hw,
+					      unsigned long prate)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+	unsigned int reg, div;
+
+	regmap_read(clk->regmap, clk->offset, &reg);
+
+	/* Handle pre-divider first */
+	if (prate != AC100_RTC_32K_RATE) {
+		div = (reg >> AC100_CLKOUT_PRE_DIV_SHIFT) &
+			((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1);
+		prate = divider_recalc_rate(hw, prate, div,
+					    ac100_clkout_prediv, 0,
+					    AC100_CLKOUT_PRE_DIV_WIDTH);
+	}
+
+	div = (reg >> AC100_CLKOUT_DIV_SHIFT) &
+		(BIT(AC100_CLKOUT_DIV_WIDTH) - 1);
+	return divider_recalc_rate(hw, prate, div, NULL,
+				   CLK_DIVIDER_POWER_OF_TWO,
+				   AC100_CLKOUT_DIV_WIDTH);
+}
+
+static long ac100_clkout_round_rate(struct clk_hw *hw, unsigned long rate,
+				    unsigned long prate)
+{
+	unsigned long best_rate = 0, tmp_rate, tmp_prate;
+	int i;
+
+	if (prate == AC100_RTC_32K_RATE)
+		return divider_round_rate(hw, rate, &prate, NULL,
+					  AC100_CLKOUT_DIV_WIDTH,
+					  CLK_DIVIDER_POWER_OF_TWO);
+
+	for (i = 0; ac100_clkout_prediv[i].div; i++) {
+		tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[i].val);
+		tmp_rate = divider_round_rate(hw, rate, &tmp_prate, NULL,
+					      AC100_CLKOUT_DIV_WIDTH,
+					      CLK_DIVIDER_POWER_OF_TWO);
+
+		if (tmp_rate > rate)
+			continue;
+		if (rate - tmp_rate < best_rate - tmp_rate)
+			best_rate = tmp_rate;
+	}
+
+	return best_rate;
+}
+
+static int ac100_clkout_determine_rate(struct clk_hw *hw,
+				       struct clk_rate_request *req)
+{
+	struct clk_hw *best_parent;
+	unsigned long best = 0;
+	int i, num_parents = clk_hw_get_num_parents(hw);
+
+	for (i = 0; i < num_parents; i++) {
+		struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
+		unsigned long tmp, prate;
+
+		/*
+		 * The clock has two parents, one is a fixed clock which is
+		 * internally registered by the ac100 driver. The other parent
+		 * is a clock from the codec side of the chip, which we
+		 * properly declare and reference in the devicetree and is
+		 * not implemented in any driver right now.
+		 * If the clock core looks for the parent of that second
+		 * missing clock, it can't find one that is registered and
+		 * returns NULL.
+		 * So we end up in a situation where clk_hw_get_num_parents
+		 * returns the amount of clocks we can be parented to, but
+		 * clk_hw_get_parent_by_index will not return the orphan
+		 * clocks.
+		 * Thus we need to check if the parent exists before
+		 * we get the parent rate, so we could use the RTC
+		 * without waiting for the codec to be supported.
+		 */
+		if (!parent)
+			continue;
+
+		prate = clk_hw_get_rate(parent);
+
+		tmp = ac100_clkout_round_rate(hw, req->rate, prate);
+
+		if (tmp > req->rate)
+			continue;
+		if (req->rate - tmp < req->rate - best) {
+			best = tmp;
+			best_parent = parent;
+		}
+	}
+
+	if (!best)
+		return -EINVAL;
+
+	req->best_parent_hw = best_parent;
+	req->best_parent_rate = best;
+	req->rate = best;
+
+	return 0;
+}
+
+static int ac100_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
+				 unsigned long prate)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+	int div = 0, pre_div = 0;
+
+	do {
+		div = divider_get_val(rate * ac100_clkout_prediv[pre_div].div,
+				      prate, NULL, AC100_CLKOUT_DIV_WIDTH,
+				      CLK_DIVIDER_POWER_OF_TWO);
+		if (div >= 0)
+			break;
+	} while (prate != AC100_RTC_32K_RATE &&
+		 ac100_clkout_prediv[++pre_div].div);
+
+	if (div < 0)
+		return div;
+
+	pre_div = ac100_clkout_prediv[pre_div].val;
+
+	regmap_update_bits(clk->regmap, clk->offset,
+			   ((1 << AC100_CLKOUT_DIV_WIDTH) - 1) << AC100_CLKOUT_DIV_SHIFT |
+			   ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
+			   (div - 1) << AC100_CLKOUT_DIV_SHIFT |
+			   (pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);
+
+	return 0;
+}
+
+static int ac100_clkout_prepare(struct clk_hw *hw)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+
+	return regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN,
+				  AC100_CLKOUT_EN);
+}
+
+static void ac100_clkout_unprepare(struct clk_hw *hw)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+
+	regmap_update_bits(clk->regmap, clk->offset, AC100_CLKOUT_EN, 0);
+}
+
+static int ac100_clkout_is_prepared(struct clk_hw *hw)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+	unsigned int reg;
+
+	regmap_read(clk->regmap, clk->offset, &reg);
+
+	return reg & AC100_CLKOUT_EN;
+}
+
+static u8 ac100_clkout_get_parent(struct clk_hw *hw)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+	unsigned int reg;
+
+	regmap_read(clk->regmap, clk->offset, &reg);
+
+	return (reg >> AC100_CLKOUT_MUX_SHIFT) & 0x1;
+}
+
+static int ac100_clkout_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct ac100_clkout *clk = to_ac100_clkout(hw);
+
+	return regmap_update_bits(clk->regmap, clk->offset,
+				  BIT(AC100_CLKOUT_MUX_SHIFT),
+				  index ? BIT(AC100_CLKOUT_MUX_SHIFT) : 0);
+}
+
+static const struct clk_ops ac100_clkout_ops = {
+	.prepare	= ac100_clkout_prepare,
+	.unprepare	= ac100_clkout_unprepare,
+	.is_prepared	= ac100_clkout_is_prepared,
+	.recalc_rate	= ac100_clkout_recalc_rate,
+	.determine_rate	= ac100_clkout_determine_rate,
+	.get_parent	= ac100_clkout_get_parent,
+	.set_parent	= ac100_clkout_set_parent,
+	.set_rate	= ac100_clkout_set_rate,
+};
+
+static int ac100_rtc_register_clks(struct ac100_rtc_dev *chip)
+{
+	struct device_node *np = chip->dev->of_node;
+	const char *parents[2] = {AC100_RTC_32K_NAME};
+	int i, ret;
+
+	chip->clk_data = devm_kzalloc(chip->dev,
+				      struct_size(chip->clk_data, hws,
+						  AC100_CLKOUT_NUM),
+				      GFP_KERNEL);
+	if (!chip->clk_data)
+		return -ENOMEM;
+
+	chip->rtc_32k_clk = clk_hw_register_fixed_rate(chip->dev,
+						       AC100_RTC_32K_NAME,
+						       NULL, 0,
+						       AC100_RTC_32K_RATE);
+	if (IS_ERR(chip->rtc_32k_clk)) {
+		ret = PTR_ERR(chip->rtc_32k_clk);
+		dev_err(chip->dev, "Failed to register RTC-32k clock: %d\n",
+			ret);
+		return ret;
+	}
+
+	parents[1] = of_clk_get_parent_name(np, 0);
+	if (!parents[1]) {
+		dev_err(chip->dev, "Failed to get ADDA 4M clock\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < AC100_CLKOUT_NUM; i++) {
+		struct ac100_clkout *clk = &chip->clks[i];
+		struct clk_init_data init = {
+			.name = ac100_clkout_names[i],
+			.ops = &ac100_clkout_ops,
+			.parent_names = parents,
+			.num_parents = ARRAY_SIZE(parents),
+			.flags = 0,
+		};
+
+		of_property_read_string_index(np, "clock-output-names",
+					      i, &init.name);
+		clk->regmap = chip->regmap;
+		clk->offset = AC100_CLKOUT_CTRL1 + i;
+		clk->hw.init = &init;
+
+		ret = devm_clk_hw_register(chip->dev, &clk->hw);
+		if (ret) {
+			dev_err(chip->dev, "Failed to register clk '%s': %d\n",
+				init.name, ret);
+			goto err_unregister_rtc_32k;
+		}
+
+		chip->clk_data->hws[i] = &clk->hw;
+	}
+
+	chip->clk_data->num = i;
+	ret = of_clk_add_hw_provider(np, of_clk_hw_onecell_get, chip->clk_data);
+	if (ret)
+		goto err_unregister_rtc_32k;
+
+	return 0;
+
+err_unregister_rtc_32k:
+	clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
+
+	return ret;
+}
+
+static void ac100_rtc_unregister_clks(struct ac100_rtc_dev *chip)
+{
+	of_clk_del_provider(chip->dev->of_node);
+	clk_unregister_fixed_rate(chip->rtc_32k_clk->clk);
+}
+
+/**
+ * RTC related bits
+ */
+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) - 1;
+	rtc_tm->tm_year = bcd2bin(reg[6] & AC100_RTC_YEA_MASK) +
+			  AC100_YEAR_OFF;
+
+	return 0;
+}
+
+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 - AC100_YEAR_OFF;
+	if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
+		dev_err(dev, "rtc only supports year in range %d - %d\n",
+			AC100_YEAR_MIN, AC100_YEAR_MAX);
+		return -EINVAL;
+	}
+
+	/* 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 + 1) & AC100_RTC_MON_MASK;
+	reg[6] = bin2bcd(year)		     & AC100_RTC_YEA_MASK;
+	/* trigger write */
+	reg[7] = AC100_RTC_UPD_TRIGGER;
+
+	/* Is it a leap year? */
+	if (is_leap_year(year + AC100_YEAR_OFF + 1900))
+		reg[6] |= AC100_RTC_YEA_LEAP;
+
+	return regmap_bulk_write(regmap, AC100_RTC_SEC, reg, 8);
+}
+
+static int ac100_rtc_alarm_irq_enable(struct device *dev, unsigned int en)
+{
+	struct ac100_rtc_dev *chip = dev_get_drvdata(dev);
+	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_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;
+
+	ret = regmap_read(regmap, AC100_ALM_INT_ENA, &val);
+	if (ret)
+		return ret;
+
+	alrm->enabled = !!(val & AC100_ALM_INT_ENABLE);
+
+	ret = regmap_bulk_read(regmap, AC100_ALM_SEC, reg, 7);
+	if (ret)
+		return ret;
+
+	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) - 1;
+	alrm_tm->tm_year = bcd2bin(reg[6] & AC100_ALM_YEA_MASK) +
+			   AC100_YEAR_OFF;
+
+	return 0;
+}
+
+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 - AC100_YEAR_OFF;
+	if (year < 0 || year > (AC100_YEAR_MAX - 1900)) {
+		dev_err(dev, "alarm only supports year in range %d - %d\n",
+			AC100_YEAR_MIN, AC100_YEAR_MAX);
+		return -EINVAL;
+	}
+
+	/* 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 + 1)  & AC100_ALM_MON_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	reg[6] = (bin2bcd(year) & AC100_ALM_YEA_MASK) |
+			AC100_ALM_ENABLE_FLAG;
+	/* trigger write */
+	reg[7] = AC100_ALM_UPD_TRIGGER;
+
+	ret = regmap_bulk_write(regmap, AC100_ALM_SEC, reg, 8);
+	if (ret)
+		return ret;
+
+	return ac100_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+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->rtc->ops_lock);
+
+	/* 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->dev, 0);
+		if (ret)
+			goto out;
+	}
+
+out:
+	mutex_unlock(&chip->rtc->ops_lock);
+	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);
+	if (!chip)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, chip);
+	chip->dev = &pdev->dev;
+	chip->regmap = ac100->regmap;
+
+	chip->irq = platform_get_irq(pdev, 0);
+	if (chip->irq < 0) {
+		dev_err(&pdev->dev, "No IRQ resource\n");
+		return chip->irq;
+	}
+
+	chip->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(chip->rtc))
+		return PTR_ERR(chip->rtc);
+
+	chip->rtc->ops = &ac100_rtc_ops;
+
+	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);
+
+	ret = ac100_rtc_register_clks(chip);
+	if (ret)
+		return ret;
+
+	ret = rtc_register_device(chip->rtc);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to register device\n");
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "RTC enabled\n");
+
+	return 0;
+}
+
+static int ac100_rtc_remove(struct platform_device *pdev)
+{
+	struct ac100_rtc_dev *chip = platform_get_drvdata(pdev);
+
+	ac100_rtc_unregister_clks(chip);
+
+	return 0;
+}
+
+static const struct of_device_id ac100_rtc_match[] = {
+	{ .compatible = "x-powers,ac100-rtc" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ac100_rtc_match);
+
+static struct platform_driver ac100_rtc_driver = {
+	.probe		= ac100_rtc_probe,
+	.remove		= ac100_rtc_remove,
+	.driver		= {
+		.name		= "ac100-rtc",
+		.of_match_table	= of_match_ptr(ac100_rtc_match),
+	},
+};
+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");