Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 642 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
new file mode 100644
index 000000000..bba7115ff
--- /dev/null
+++ b/drivers/rtc/rtc-ac100.c
@@ -0,0 +1,642 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RTC Driver for X-Powers AC100
+ *
+ * Copyright (c) 2016 Chen-Yu Tsai
+ *
+ * Chen-Yu Tsai <wens@csie.org>
+ */
+
+#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 int ac100_clkout_determine_rate(struct clk_hw *hw,
+				       struct clk_rate_request *req)
+{
+	int i, ret, num_parents = clk_hw_get_num_parents(hw);
+	struct clk_hw *best_parent = NULL;
+	unsigned long best = 0;
+
+	for (i = 0; i < num_parents; i++) {
+		struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
+		unsigned long 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);
+
+		if (prate == AC100_RTC_32K_RATE) {
+			struct clk_rate_request div_req = *req;
+
+			div_req.best_parent_rate = prate;
+
+			ret = divider_determine_rate(hw, &div_req, NULL,
+						     AC100_CLKOUT_DIV_WIDTH,
+						     CLK_DIVIDER_POWER_OF_TWO);
+			if (ret != 0 || div_req.rate > req->rate) {
+				continue;
+			} else if (req->rate - div_req.rate < req->rate - best) {
+				best = div_req.rate;
+				best_parent = parent;
+			}
+		} else {
+			int j;
+
+			for (j = 0; ac100_clkout_prediv[j].div; j++) {
+				struct clk_rate_request div_req = *req;
+				unsigned long tmp_prate;
+
+				tmp_prate = DIV_ROUND_UP(prate, ac100_clkout_prediv[j].div);
+				div_req.best_parent_rate = tmp_prate;
+
+				ret = divider_determine_rate(hw, &div_req, NULL,
+							     AC100_CLKOUT_DIV_WIDTH,
+							     CLK_DIVIDER_POWER_OF_TWO);
+				if (ret != 0 || div_req.rate > req->rate) {
+					continue;
+				} else if (req->rate - div_req.rate < req->rate - best) {
+					best = div_req.rate;
+					best_parent = parent;
+				}
+			}
+		}
+	}
+
+	if (!best)
+		return -EINVAL;
+
+	req->best_parent_hw = best_parent;
+	req->best_parent_rate = clk_hw_get_rate(best_parent);
+	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;
+
+	rtc_lock(chip->rtc);
+
+	/* 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:
+	rtc_unlock(chip->rtc);
+	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)
+		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;
+
+	return devm_rtc_register_device(chip->rtc);
+}
+
+static void ac100_rtc_remove(struct platform_device *pdev)
+{
+	struct ac100_rtc_dev *chip = platform_get_drvdata(pdev);
+
+	ac100_rtc_unregister_clks(chip);
+}
+
+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");