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, 747 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-ds1305.c b/drivers/rtc/rtc-ds1305.c
new file mode 100644
index 000000000..d4de40154
--- /dev/null
+++ b/drivers/rtc/rtc-ds1305.c
@@ -0,0 +1,747 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * rtc-ds1305.c -- driver for DS1305 and DS1306 SPI RTC chips
+ *
+ * Copyright (C) 2008 David Brownell
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/bcd.h>
+#include <linux/slab.h>
+#include <linux/rtc.h>
+#include <linux/workqueue.h>
+
+#include <linux/spi/spi.h>
+#include <linux/spi/ds1305.h>
+#include <linux/module.h>
+
+
+/*
+ * Registers ... mask DS1305_WRITE into register address to write,
+ * otherwise you're reading it.  All non-bitmask values are BCD.
+ */
+#define DS1305_WRITE		0x80
+
+
+/* RTC date/time ... the main special cases are that we:
+ *  - Need fancy "hours" encoding in 12hour mode
+ *  - Don't rely on the "day-of-week" field (or tm_wday)
+ *  - Are a 21st-century clock (2000 <= year < 2100)
+ */
+#define DS1305_RTC_LEN		7		/* bytes for RTC regs */
+
+#define DS1305_SEC		0x00		/* register addresses */
+#define DS1305_MIN		0x01
+#define DS1305_HOUR		0x02
+#	define DS1305_HR_12		0x40	/* set == 12 hr mode */
+#	define DS1305_HR_PM		0x20	/* set == PM (12hr mode) */
+#define DS1305_WDAY		0x03
+#define DS1305_MDAY		0x04
+#define DS1305_MON		0x05
+#define DS1305_YEAR		0x06
+
+
+/* The two alarms have only sec/min/hour/wday fields (ALM_LEN).
+ * DS1305_ALM_DISABLE disables a match field (some combos are bad).
+ *
+ * NOTE that since we don't use WDAY, we limit ourselves to alarms
+ * only one day into the future (vs potentially up to a week).
+ *
+ * NOTE ALSO that while we could generate once-a-second IRQs (UIE), we
+ * don't currently support them.  We'd either need to do it only when
+ * no alarm is pending (not the standard model), or to use the second
+ * alarm (implying that this is a DS1305 not DS1306, *and* that either
+ * it's wired up a second IRQ we know, or that INTCN is set)
+ */
+#define DS1305_ALM_LEN		4		/* bytes for ALM regs */
+#define DS1305_ALM_DISABLE	0x80
+
+#define DS1305_ALM0(r)		(0x07 + (r))	/* register addresses */
+#define DS1305_ALM1(r)		(0x0b + (r))
+
+
+/* three control registers */
+#define DS1305_CONTROL_LEN	3		/* bytes of control regs */
+
+#define DS1305_CONTROL		0x0f		/* register addresses */
+#	define DS1305_nEOSC		0x80	/* low enables oscillator */
+#	define DS1305_WP		0x40	/* write protect */
+#	define DS1305_INTCN		0x04	/* clear == only int0 used */
+#	define DS1306_1HZ		0x04	/* enable 1Hz output */
+#	define DS1305_AEI1		0x02	/* enable ALM1 IRQ */
+#	define DS1305_AEI0		0x01	/* enable ALM0 IRQ */
+#define DS1305_STATUS		0x10
+/* status has just AEIx bits, mirrored as IRQFx */
+#define DS1305_TRICKLE		0x11
+/* trickle bits are defined in <linux/spi/ds1305.h> */
+
+/* a bunch of NVRAM */
+#define DS1305_NVRAM_LEN	96		/* bytes of NVRAM */
+
+#define DS1305_NVRAM		0x20		/* register addresses */
+
+
+struct ds1305 {
+	struct spi_device	*spi;
+	struct rtc_device	*rtc;
+
+	struct work_struct	work;
+
+	unsigned long		flags;
+#define FLAG_EXITING	0
+
+	bool			hr12;
+	u8			ctrl[DS1305_CONTROL_LEN];
+};
+
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * Utilities ...  tolerate 12-hour AM/PM notation in case of non-Linux
+ * software (like a bootloader) which may require it.
+ */
+
+static unsigned bcd2hour(u8 bcd)
+{
+	if (bcd & DS1305_HR_12) {
+		unsigned	hour = 0;
+
+		bcd &= ~DS1305_HR_12;
+		if (bcd & DS1305_HR_PM) {
+			hour = 12;
+			bcd &= ~DS1305_HR_PM;
+		}
+		hour += bcd2bin(bcd);
+		return hour - 1;
+	}
+	return bcd2bin(bcd);
+}
+
+static u8 hour2bcd(bool hr12, int hour)
+{
+	if (hr12) {
+		hour++;
+		if (hour <= 12)
+			return DS1305_HR_12 | bin2bcd(hour);
+		hour -= 12;
+		return DS1305_HR_12 | DS1305_HR_PM | bin2bcd(hour);
+	}
+	return bin2bcd(hour);
+}
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * Interface to RTC framework
+ */
+
+static int ds1305_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	u8		buf[2];
+	long		err = -EINVAL;
+
+	buf[0] = DS1305_WRITE | DS1305_CONTROL;
+	buf[1] = ds1305->ctrl[0];
+
+	if (enabled) {
+		if (ds1305->ctrl[0] & DS1305_AEI0)
+			goto done;
+		buf[1] |= DS1305_AEI0;
+	} else {
+		if (!(buf[1] & DS1305_AEI0))
+			goto done;
+		buf[1] &= ~DS1305_AEI0;
+	}
+	err = spi_write_then_read(ds1305->spi, buf, sizeof(buf), NULL, 0);
+	if (err >= 0)
+		ds1305->ctrl[0] = buf[1];
+done:
+	return err;
+
+}
+
+
+/*
+ * Get/set of date and time is pretty normal.
+ */
+
+static int ds1305_get_time(struct device *dev, struct rtc_time *time)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	u8		addr = DS1305_SEC;
+	u8		buf[DS1305_RTC_LEN];
+	int		status;
+
+	/* Use write-then-read to get all the date/time registers
+	 * since dma from stack is nonportable
+	 */
+	status = spi_write_then_read(ds1305->spi, &addr, sizeof(addr),
+			buf, sizeof(buf));
+	if (status < 0)
+		return status;
+
+	dev_vdbg(dev, "%s: %3ph, %4ph\n", "read", &buf[0], &buf[3]);
+
+	/* Decode the registers */
+	time->tm_sec = bcd2bin(buf[DS1305_SEC]);
+	time->tm_min = bcd2bin(buf[DS1305_MIN]);
+	time->tm_hour = bcd2hour(buf[DS1305_HOUR]);
+	time->tm_wday = buf[DS1305_WDAY] - 1;
+	time->tm_mday = bcd2bin(buf[DS1305_MDAY]);
+	time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1;
+	time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100;
+
+	dev_vdbg(dev, "%s secs=%d, mins=%d, "
+		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+		"read", time->tm_sec, time->tm_min,
+		time->tm_hour, time->tm_mday,
+		time->tm_mon, time->tm_year, time->tm_wday);
+
+	return 0;
+}
+
+static int ds1305_set_time(struct device *dev, struct rtc_time *time)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	u8		buf[1 + DS1305_RTC_LEN];
+	u8		*bp = buf;
+
+	dev_vdbg(dev, "%s secs=%d, mins=%d, "
+		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
+		"write", time->tm_sec, time->tm_min,
+		time->tm_hour, time->tm_mday,
+		time->tm_mon, time->tm_year, time->tm_wday);
+
+	/* Write registers starting at the first time/date address. */
+	*bp++ = DS1305_WRITE | DS1305_SEC;
+
+	*bp++ = bin2bcd(time->tm_sec);
+	*bp++ = bin2bcd(time->tm_min);
+	*bp++ = hour2bcd(ds1305->hr12, time->tm_hour);
+	*bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1;
+	*bp++ = bin2bcd(time->tm_mday);
+	*bp++ = bin2bcd(time->tm_mon + 1);
+	*bp++ = bin2bcd(time->tm_year - 100);
+
+	dev_dbg(dev, "%s: %3ph, %4ph\n", "write", &buf[1], &buf[4]);
+
+	/* use write-then-read since dma from stack is nonportable */
+	return spi_write_then_read(ds1305->spi, buf, sizeof(buf),
+			NULL, 0);
+}
+
+/*
+ * Get/set of alarm is a bit funky:
+ *
+ * - First there's the inherent raciness of getting the (partitioned)
+ *   status of an alarm that could trigger while we're reading parts
+ *   of that status.
+ *
+ * - Second there's its limited range (we could increase it a bit by
+ *   relying on WDAY), which means it will easily roll over.
+ *
+ * - Third there's the choice of two alarms and alarm signals.
+ *   Here we use ALM0 and expect that nINT0 (open drain) is used;
+ *   that's the only real option for DS1306 runtime alarms, and is
+ *   natural on DS1305.
+ *
+ * - Fourth, there's also ALM1, and a second interrupt signal:
+ *     + On DS1305 ALM1 uses nINT1 (when INTCN=1) else nINT0;
+ *     + On DS1306 ALM1 only uses INT1 (an active high pulse)
+ *       and it won't work when VCC1 is active.
+ *
+ *   So to be most general, we should probably set both alarms to the
+ *   same value, letting ALM1 be the wakeup event source on DS1306
+ *   and handling several wiring options on DS1305.
+ *
+ * - Fifth, we support the polled mode (as well as possible; why not?)
+ *   even when no interrupt line is wired to an IRQ.
+ */
+
+/*
+ * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
+ */
+static int ds1305_get_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	struct spi_device *spi = ds1305->spi;
+	u8		addr;
+	int		status;
+	u8		buf[DS1305_ALM_LEN];
+
+	/* Refresh control register cache BEFORE reading ALM0 registers,
+	 * since reading alarm registers acks any pending IRQ.  That
+	 * makes returning "pending" status a bit of a lie, but that bit
+	 * of EFI status is at best fragile anyway (given IRQ handlers).
+	 */
+	addr = DS1305_CONTROL;
+	status = spi_write_then_read(spi, &addr, sizeof(addr),
+			ds1305->ctrl, sizeof(ds1305->ctrl));
+	if (status < 0)
+		return status;
+
+	alm->enabled = !!(ds1305->ctrl[0] & DS1305_AEI0);
+	alm->pending = !!(ds1305->ctrl[1] & DS1305_AEI0);
+
+	/* get and check ALM0 registers */
+	addr = DS1305_ALM0(DS1305_SEC);
+	status = spi_write_then_read(spi, &addr, sizeof(addr),
+			buf, sizeof(buf));
+	if (status < 0)
+		return status;
+
+	dev_vdbg(dev, "%s: %02x %02x %02x %02x\n",
+		"alm0 read", buf[DS1305_SEC], buf[DS1305_MIN],
+		buf[DS1305_HOUR], buf[DS1305_WDAY]);
+
+	if ((DS1305_ALM_DISABLE & buf[DS1305_SEC])
+			|| (DS1305_ALM_DISABLE & buf[DS1305_MIN])
+			|| (DS1305_ALM_DISABLE & buf[DS1305_HOUR]))
+		return -EIO;
+
+	/* Stuff these values into alm->time and let RTC framework code
+	 * fill in the rest ... and also handle rollover to tomorrow when
+	 * that's needed.
+	 */
+	alm->time.tm_sec = bcd2bin(buf[DS1305_SEC]);
+	alm->time.tm_min = bcd2bin(buf[DS1305_MIN]);
+	alm->time.tm_hour = bcd2hour(buf[DS1305_HOUR]);
+
+	return 0;
+}
+
+/*
+ * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl)
+ */
+static int ds1305_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	struct spi_device *spi = ds1305->spi;
+	unsigned long	now, later;
+	struct rtc_time	tm;
+	int		status;
+	u8		buf[1 + DS1305_ALM_LEN];
+
+	/* convert desired alarm to time_t */
+	later = rtc_tm_to_time64(&alm->time);
+
+	/* Read current time as time_t */
+	status = ds1305_get_time(dev, &tm);
+	if (status < 0)
+		return status;
+	now = rtc_tm_to_time64(&tm);
+
+	/* make sure alarm fires within the next 24 hours */
+	if (later <= now)
+		return -EINVAL;
+	if ((later - now) > ds1305->rtc->alarm_offset_max)
+		return -ERANGE;
+
+	/* disable alarm if needed */
+	if (ds1305->ctrl[0] & DS1305_AEI0) {
+		ds1305->ctrl[0] &= ~DS1305_AEI0;
+
+		buf[0] = DS1305_WRITE | DS1305_CONTROL;
+		buf[1] = ds1305->ctrl[0];
+		status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
+		if (status < 0)
+			return status;
+	}
+
+	/* write alarm */
+	buf[0] = DS1305_WRITE | DS1305_ALM0(DS1305_SEC);
+	buf[1 + DS1305_SEC] = bin2bcd(alm->time.tm_sec);
+	buf[1 + DS1305_MIN] = bin2bcd(alm->time.tm_min);
+	buf[1 + DS1305_HOUR] = hour2bcd(ds1305->hr12, alm->time.tm_hour);
+	buf[1 + DS1305_WDAY] = DS1305_ALM_DISABLE;
+
+	dev_dbg(dev, "%s: %02x %02x %02x %02x\n",
+		"alm0 write", buf[1 + DS1305_SEC], buf[1 + DS1305_MIN],
+		buf[1 + DS1305_HOUR], buf[1 + DS1305_WDAY]);
+
+	status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
+	if (status < 0)
+		return status;
+
+	/* enable alarm if requested */
+	if (alm->enabled) {
+		ds1305->ctrl[0] |= DS1305_AEI0;
+
+		buf[0] = DS1305_WRITE | DS1305_CONTROL;
+		buf[1] = ds1305->ctrl[0];
+		status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0);
+	}
+
+	return status;
+}
+
+#ifdef CONFIG_PROC_FS
+
+static int ds1305_proc(struct device *dev, struct seq_file *seq)
+{
+	struct ds1305	*ds1305 = dev_get_drvdata(dev);
+	char		*diodes = "no";
+	char		*resistors = "";
+
+	/* ctrl[2] is treated as read-only; no locking needed */
+	if ((ds1305->ctrl[2] & 0xf0) == DS1305_TRICKLE_MAGIC) {
+		switch (ds1305->ctrl[2] & 0x0c) {
+		case DS1305_TRICKLE_DS2:
+			diodes = "2 diodes, ";
+			break;
+		case DS1305_TRICKLE_DS1:
+			diodes = "1 diode, ";
+			break;
+		default:
+			goto done;
+		}
+		switch (ds1305->ctrl[2] & 0x03) {
+		case DS1305_TRICKLE_2K:
+			resistors = "2k Ohm";
+			break;
+		case DS1305_TRICKLE_4K:
+			resistors = "4k Ohm";
+			break;
+		case DS1305_TRICKLE_8K:
+			resistors = "8k Ohm";
+			break;
+		default:
+			diodes = "no";
+			break;
+		}
+	}
+
+done:
+	seq_printf(seq, "trickle_charge\t: %s%s\n", diodes, resistors);
+
+	return 0;
+}
+
+#else
+#define ds1305_proc	NULL
+#endif
+
+static const struct rtc_class_ops ds1305_ops = {
+	.read_time	= ds1305_get_time,
+	.set_time	= ds1305_set_time,
+	.read_alarm	= ds1305_get_alarm,
+	.set_alarm	= ds1305_set_alarm,
+	.proc		= ds1305_proc,
+	.alarm_irq_enable = ds1305_alarm_irq_enable,
+};
+
+static void ds1305_work(struct work_struct *work)
+{
+	struct ds1305	*ds1305 = container_of(work, struct ds1305, work);
+	struct spi_device *spi = ds1305->spi;
+	u8		buf[3];
+	int		status;
+
+	/* lock to protect ds1305->ctrl */
+	rtc_lock(ds1305->rtc);
+
+	/* Disable the IRQ, and clear its status ... for now, we "know"
+	 * that if more than one alarm is active, they're in sync.
+	 * Note that reading ALM data registers also clears IRQ status.
+	 */
+	ds1305->ctrl[0] &= ~(DS1305_AEI1 | DS1305_AEI0);
+	ds1305->ctrl[1] = 0;
+
+	buf[0] = DS1305_WRITE | DS1305_CONTROL;
+	buf[1] = ds1305->ctrl[0];
+	buf[2] = 0;
+
+	status = spi_write_then_read(spi, buf, sizeof(buf),
+			NULL, 0);
+	if (status < 0)
+		dev_dbg(&spi->dev, "clear irq --> %d\n", status);
+
+	rtc_unlock(ds1305->rtc);
+
+	if (!test_bit(FLAG_EXITING, &ds1305->flags))
+		enable_irq(spi->irq);
+
+	rtc_update_irq(ds1305->rtc, 1, RTC_AF | RTC_IRQF);
+}
+
+/*
+ * This "real" IRQ handler hands off to a workqueue mostly to allow
+ * mutex locking for ds1305->ctrl ... unlike I2C, we could issue async
+ * I/O requests in IRQ context (to clear the IRQ status).
+ */
+static irqreturn_t ds1305_irq(int irq, void *p)
+{
+	struct ds1305		*ds1305 = p;
+
+	disable_irq(irq);
+	schedule_work(&ds1305->work);
+	return IRQ_HANDLED;
+}
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * Interface for NVRAM
+ */
+
+static void msg_init(struct spi_message *m, struct spi_transfer *x,
+		u8 *addr, size_t count, char *tx, char *rx)
+{
+	spi_message_init(m);
+	memset(x, 0, 2 * sizeof(*x));
+
+	x->tx_buf = addr;
+	x->len = 1;
+	spi_message_add_tail(x, m);
+
+	x++;
+
+	x->tx_buf = tx;
+	x->rx_buf = rx;
+	x->len = count;
+	spi_message_add_tail(x, m);
+}
+
+static int ds1305_nvram_read(void *priv, unsigned int off, void *buf,
+			     size_t count)
+{
+	struct ds1305		*ds1305 = priv;
+	struct spi_device	*spi = ds1305->spi;
+	u8			addr;
+	struct spi_message	m;
+	struct spi_transfer	x[2];
+
+	addr = DS1305_NVRAM + off;
+	msg_init(&m, x, &addr, count, NULL, buf);
+
+	return spi_sync(spi, &m);
+}
+
+static int ds1305_nvram_write(void *priv, unsigned int off, void *buf,
+			      size_t count)
+{
+	struct ds1305		*ds1305 = priv;
+	struct spi_device	*spi = ds1305->spi;
+	u8			addr;
+	struct spi_message	m;
+	struct spi_transfer	x[2];
+
+	addr = (DS1305_WRITE | DS1305_NVRAM) + off;
+	msg_init(&m, x, &addr, count, buf, NULL);
+
+	return spi_sync(spi, &m);
+}
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * Interface to SPI stack
+ */
+
+static int ds1305_probe(struct spi_device *spi)
+{
+	struct ds1305			*ds1305;
+	int				status;
+	u8				addr, value;
+	struct ds1305_platform_data	*pdata = dev_get_platdata(&spi->dev);
+	bool				write_ctrl = false;
+	struct nvmem_config ds1305_nvmem_cfg = {
+		.name = "ds1305_nvram",
+		.word_size = 1,
+		.stride = 1,
+		.size = DS1305_NVRAM_LEN,
+		.reg_read = ds1305_nvram_read,
+		.reg_write = ds1305_nvram_write,
+	};
+
+	/* Sanity check board setup data.  This may be hooked up
+	 * in 3wire mode, but we don't care.  Note that unless
+	 * there's an inverter in place, this needs SPI_CS_HIGH!
+	 */
+	if ((spi->bits_per_word && spi->bits_per_word != 8)
+			|| (spi->max_speed_hz > 2000000)
+			|| !(spi->mode & SPI_CPHA))
+		return -EINVAL;
+
+	/* set up driver data */
+	ds1305 = devm_kzalloc(&spi->dev, sizeof(*ds1305), GFP_KERNEL);
+	if (!ds1305)
+		return -ENOMEM;
+	ds1305->spi = spi;
+	spi_set_drvdata(spi, ds1305);
+
+	/* read and cache control registers */
+	addr = DS1305_CONTROL;
+	status = spi_write_then_read(spi, &addr, sizeof(addr),
+			ds1305->ctrl, sizeof(ds1305->ctrl));
+	if (status < 0) {
+		dev_dbg(&spi->dev, "can't %s, %d\n",
+				"read", status);
+		return status;
+	}
+
+	dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "read", ds1305->ctrl);
+
+	/* Sanity check register values ... partially compensating for the
+	 * fact that SPI has no device handshake.  A pullup on MISO would
+	 * make these tests fail; but not all systems will have one.  If
+	 * some register is neither 0x00 nor 0xff, a chip is likely there.
+	 */
+	if ((ds1305->ctrl[0] & 0x38) != 0 || (ds1305->ctrl[1] & 0xfc) != 0) {
+		dev_dbg(&spi->dev, "RTC chip is not present\n");
+		return -ENODEV;
+	}
+	if (ds1305->ctrl[2] == 0)
+		dev_dbg(&spi->dev, "chip may not be present\n");
+
+	/* enable writes if needed ... if we were paranoid it would
+	 * make sense to enable them only when absolutely necessary.
+	 */
+	if (ds1305->ctrl[0] & DS1305_WP) {
+		u8		buf[2];
+
+		ds1305->ctrl[0] &= ~DS1305_WP;
+
+		buf[0] = DS1305_WRITE | DS1305_CONTROL;
+		buf[1] = ds1305->ctrl[0];
+		status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
+
+		dev_dbg(&spi->dev, "clear WP --> %d\n", status);
+		if (status < 0)
+			return status;
+	}
+
+	/* on DS1305, maybe start oscillator; like most low power
+	 * oscillators, it may take a second to stabilize
+	 */
+	if (ds1305->ctrl[0] & DS1305_nEOSC) {
+		ds1305->ctrl[0] &= ~DS1305_nEOSC;
+		write_ctrl = true;
+		dev_warn(&spi->dev, "SET TIME!\n");
+	}
+
+	/* ack any pending IRQs */
+	if (ds1305->ctrl[1]) {
+		ds1305->ctrl[1] = 0;
+		write_ctrl = true;
+	}
+
+	/* this may need one-time (re)init */
+	if (pdata) {
+		/* maybe enable trickle charge */
+		if (((ds1305->ctrl[2] & 0xf0) != DS1305_TRICKLE_MAGIC)) {
+			ds1305->ctrl[2] = DS1305_TRICKLE_MAGIC
+						| pdata->trickle;
+			write_ctrl = true;
+		}
+
+		/* on DS1306, configure 1 Hz signal */
+		if (pdata->is_ds1306) {
+			if (pdata->en_1hz) {
+				if (!(ds1305->ctrl[0] & DS1306_1HZ)) {
+					ds1305->ctrl[0] |= DS1306_1HZ;
+					write_ctrl = true;
+				}
+			} else {
+				if (ds1305->ctrl[0] & DS1306_1HZ) {
+					ds1305->ctrl[0] &= ~DS1306_1HZ;
+					write_ctrl = true;
+				}
+			}
+		}
+	}
+
+	if (write_ctrl) {
+		u8		buf[4];
+
+		buf[0] = DS1305_WRITE | DS1305_CONTROL;
+		buf[1] = ds1305->ctrl[0];
+		buf[2] = ds1305->ctrl[1];
+		buf[3] = ds1305->ctrl[2];
+		status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
+		if (status < 0) {
+			dev_dbg(&spi->dev, "can't %s, %d\n",
+					"write", status);
+			return status;
+		}
+
+		dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "write", ds1305->ctrl);
+	}
+
+	/* see if non-Linux software set up AM/PM mode */
+	addr = DS1305_HOUR;
+	status = spi_write_then_read(spi, &addr, sizeof(addr),
+				&value, sizeof(value));
+	if (status < 0) {
+		dev_dbg(&spi->dev, "read HOUR --> %d\n", status);
+		return status;
+	}
+
+	ds1305->hr12 = (DS1305_HR_12 & value) != 0;
+	if (ds1305->hr12)
+		dev_dbg(&spi->dev, "AM/PM\n");
+
+	/* register RTC ... from here on, ds1305->ctrl needs locking */
+	ds1305->rtc = devm_rtc_allocate_device(&spi->dev);
+	if (IS_ERR(ds1305->rtc))
+		return PTR_ERR(ds1305->rtc);
+
+	ds1305->rtc->ops = &ds1305_ops;
+	ds1305->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	ds1305->rtc->range_max = RTC_TIMESTAMP_END_2099;
+	ds1305->rtc->alarm_offset_max = 24 * 60 * 60;
+
+	ds1305_nvmem_cfg.priv = ds1305;
+	status = devm_rtc_register_device(ds1305->rtc);
+	if (status)
+		return status;
+
+	devm_rtc_nvmem_register(ds1305->rtc, &ds1305_nvmem_cfg);
+
+	/* Maybe set up alarm IRQ; be ready to handle it triggering right
+	 * away.  NOTE that we don't share this.  The signal is active low,
+	 * and we can't ack it before a SPI message delay.  We temporarily
+	 * disable the IRQ until it's acked, which lets us work with more
+	 * IRQ trigger modes (not all IRQ controllers can do falling edge).
+	 */
+	if (spi->irq) {
+		INIT_WORK(&ds1305->work, ds1305_work);
+		status = devm_request_irq(&spi->dev, spi->irq, ds1305_irq,
+				0, dev_name(&ds1305->rtc->dev), ds1305);
+		if (status < 0) {
+			dev_err(&spi->dev, "request_irq %d --> %d\n",
+					spi->irq, status);
+		} else {
+			device_set_wakeup_capable(&spi->dev, 1);
+		}
+	}
+
+	return 0;
+}
+
+static void ds1305_remove(struct spi_device *spi)
+{
+	struct ds1305 *ds1305 = spi_get_drvdata(spi);
+
+	/* carefully shut down irq and workqueue, if present */
+	if (spi->irq) {
+		set_bit(FLAG_EXITING, &ds1305->flags);
+		devm_free_irq(&spi->dev, spi->irq, ds1305);
+		cancel_work_sync(&ds1305->work);
+	}
+}
+
+static struct spi_driver ds1305_driver = {
+	.driver.name	= "rtc-ds1305",
+	.probe		= ds1305_probe,
+	.remove		= ds1305_remove,
+	/* REVISIT add suspend/resume */
+};
+
+module_spi_driver(ds1305_driver);
+
+MODULE_DESCRIPTION("RTC driver for DS1305 and DS1306 chips");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:rtc-ds1305");