[PATCH 2/2] Add i.MX25 rtc driver

[Sascha Hauer <s.hauer@pengutronix.de>]

This adds a RTC driver for the Freescale i.MX25. This is done more
to get access to the nonvolatile general purpose register than it
is done to read the clock.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/rtc/Kconfig     |   6 +
 drivers/rtc/Makefile    |   1 +
 drivers/rtc/rtc-imxdi.c | 623 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 630 insertions(+)
 create mode 100644 drivers/rtc/rtc-imxdi.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 7d181949ee..9d2c6e614b 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -38,6 +38,12 @@ config RTC_DRV_ABRACON
 
 endif # I2C
 
+config RTC_DRV_IMXDI
+	tristate "Freescale IMX DryIce Real Time Clock"
+	depends on ARCH_IMX
+	help
+	   Support for Freescale IMX DryIce RTC
+
 config RTC_DRV_JZ4740
 	tristate "Ingenic JZ4740 RTC"
 	depends on MACH_MIPS_XBURST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 68741c26a1..1308beff38 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -9,4 +9,5 @@ obj-$(CONFIG_RTC_CLASS)         += class.o
 
 obj-$(CONFIG_RTC_DRV_ABRACON)   += rtc-abracon.o
 obj-$(CONFIG_RTC_DRV_DS1307)    += rtc-ds1307.o
+obj-$(CONFIG_RTC_DRV_IMXDI)	+= rtc-imxdi.o
 obj-$(CONFIG_RTC_DRV_JZ4740)	+= rtc-jz4740.o
diff --git a/drivers/rtc/rtc-imxdi.c b/drivers/rtc/rtc-imxdi.c
new file mode 100644
index 0000000000..8fcaf631ff
--- /dev/null
+++ b/drivers/rtc/rtc-imxdi.c
@@ -0,0 +1,623 @@
+/*
+ * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2010 Orex Computed Radiography
+ */
+
+/*
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+/* based on rtc-mc13892.c */
+
+/*
+ * This driver uses the 47-bit 32 kHz counter in the Freescale DryIce block
+ * to implement a Linux RTC. Times and alarms are truncated to seconds.
+ * Since the RTC framework performs API locking via rtc->ops_lock the
+ * only simultaneous accesses we need to deal with is updating DryIce
+ * registers while servicing an alarm.
+ *
+ * Note that reading the DSR (DryIce Status Register) automatically clears
+ * the WCF (Write Complete Flag). All DryIce writes are synchronized to the
+ * LP (Low Power) domain and set the WCF upon completion. Writes to the
+ * DIER (DryIce Interrupt Enable Register) are the only exception. These
+ * occur at normal bus speeds and do not set WCF.  Periodic interrupts are
+ * not supported by the hardware.
+ */
+
+#include <common.h>
+#include <driver.h>
+#include <init.h>
+#include <rtc.h>
+#include <io.h>
+#include <linux/clk.h>
+#include <linux/rtc.h>
+#include <linux/nvmem-provider.h>
+
+/* DryIce Register Definitions */
+
+#define DTCMR     0x00           /* Time Counter MSB Reg */
+#define DTCLR     0x04           /* Time Counter LSB Reg */
+
+#define DCAMR     0x08           /* Clock Alarm MSB Reg */
+#define DCALR     0x0c           /* Clock Alarm LSB Reg */
+#define DCAMR_UNSET  0xFFFFFFFF  /* doomsday - 1 sec */
+
+#define DCR       0x10           /* Control Reg */
+#define DCR_TDCHL (1 << 30)      /* Tamper-detect configuration hard lock */
+#define DCR_TDCSL (1 << 29)      /* Tamper-detect configuration soft lock */
+#define DCR_KSSL  (1 << 27)      /* Key-select soft lock */
+#define DCR_MCHL  (1 << 20)      /* Monotonic-counter hard lock */
+#define DCR_MCSL  (1 << 19)      /* Monotonic-counter soft lock */
+#define DCR_TCHL  (1 << 18)      /* Timer-counter hard lock */
+#define DCR_TCSL  (1 << 17)      /* Timer-counter soft lock */
+#define DCR_FSHL  (1 << 16)      /* Failure state hard lock */
+#define DCR_TCE   (1 << 3)       /* Time Counter Enable */
+#define DCR_MCE   (1 << 2)       /* Monotonic Counter Enable */
+
+#define DSR       0x14           /* Status Reg */
+#define DSR_WTD   (1 << 23)      /* Wire-mesh tamper detected */
+#define DSR_ETBD  (1 << 22)      /* External tamper B detected */
+#define DSR_ETAD  (1 << 21)      /* External tamper A detected */
+#define DSR_EBD   (1 << 20)      /* External boot detected */
+#define DSR_SAD   (1 << 19)      /* SCC alarm detected */
+#define DSR_TTD   (1 << 18)      /* Temperature tamper detected */
+#define DSR_CTD   (1 << 17)      /* Clock tamper detected */
+#define DSR_VTD   (1 << 16)      /* Voltage tamper detected */
+#define DSR_WBF   (1 << 10)      /* Write Busy Flag (synchronous) */
+#define DSR_WNF   (1 << 9)       /* Write Next Flag (synchronous) */
+#define DSR_WCF   (1 << 8)       /* Write Complete Flag (synchronous)*/
+#define DSR_WEF   (1 << 7)       /* Write Error Flag */
+#define DSR_CAF   (1 << 4)       /* Clock Alarm Flag */
+#define DSR_MCO   (1 << 3)       /* monotonic counter overflow */
+#define DSR_TCO   (1 << 2)       /* time counter overflow */
+#define DSR_NVF   (1 << 1)       /* Non-Valid Flag */
+#define DSR_SVF   (1 << 0)       /* Security Violation Flag */
+
+#define DIER      0x18           /* Interrupt Enable Reg (synchronous) */
+#define DIER_WNIE (1 << 9)       /* Write Next Interrupt Enable */
+#define DIER_WCIE (1 << 8)       /* Write Complete Interrupt Enable */
+#define DIER_WEIE (1 << 7)       /* Write Error Interrupt Enable */
+#define DIER_CAIE (1 << 4)       /* Clock Alarm Interrupt Enable */
+#define DIER_SVIE (1 << 0)       /* Security-violation Interrupt Enable */
+
+#define DMCR      0x1c           /* DryIce Monotonic Counter Reg */
+
+#define DTCR      0x28           /* DryIce Tamper Configuration Reg */
+#define DTCR_MOE  (1 << 9)       /* monotonic overflow enabled */
+#define DTCR_TOE  (1 << 8)       /* time overflow enabled */
+#define DTCR_WTE  (1 << 7)       /* wire-mesh tamper enabled */
+#define DTCR_ETBE (1 << 6)       /* external B tamper enabled */
+#define DTCR_ETAE (1 << 5)       /* external A tamper enabled */
+#define DTCR_EBE  (1 << 4)       /* external boot tamper enabled */
+#define DTCR_SAIE (1 << 3)       /* SCC enabled */
+#define DTCR_TTE  (1 << 2)       /* temperature tamper enabled */
+#define DTCR_CTE  (1 << 1)       /* clock tamper enabled */
+#define DTCR_VTE  (1 << 0)       /* voltage tamper enabled */
+
+#define DGPR      0x3c           /* DryIce General Purpose Reg */
+
+/**
+ * struct imxdi_dev - private imxdi rtc data
+ * @dev: pionter to dev
+ * @rtc: pointer to rtc struct
+ * @ioaddr: IO registers pointer
+ * @clk: input reference clock
+ * @dsr: copy of the DSR register
+ */
+struct imxdi_dev {
+	struct device_d *dev;
+	struct rtc_device rtc;
+	void __iomem *ioaddr;
+	struct clk *clk;
+	u32 dsr;
+	struct nvmem_device *nvmem;
+};
+
+/* Some background:
+ *
+ * The DryIce unit is a complex security/tamper monitor device. To be able do
+ * its job in a useful manner it runs a bigger statemachine to bring it into
+ * security/tamper failure state and once again to bring it out of this state.
+ *
+ * This unit can be in one of three states:
+ *
+ * - "NON-VALID STATE"
+ *   always after the battery power was removed
+ * - "FAILURE STATE"
+ *   if one of the enabled security events has happened
+ * - "VALID STATE"
+ *   if the unit works as expected
+ *
+ * Everything stops when the unit enters the failure state including the RTC
+ * counter (to be able to detect the time the security event happened).
+ *
+ * The following events (when enabled) let the DryIce unit enter the failure
+ * state:
+ *
+ * - wire-mesh-tamper detect
+ * - external tamper B detect
+ * - external tamper A detect
+ * - temperature tamper detect
+ * - clock tamper detect
+ * - voltage tamper detect
+ * - RTC counter overflow
+ * - monotonic counter overflow
+ * - external boot
+ *
+ * If we find the DryIce unit in "FAILURE STATE" and the TDCHL cleared, we
+ * can only detect this state. In this case the unit is completely locked and
+ * must force a second "SYSTEM POR" to bring the DryIce into the
+ * "NON-VALID STATE" + "FAILURE STATE" where a recovery is possible.
+ * If the TDCHL is set in the "FAILURE STATE" we are out of luck. In this case
+ * a battery power cycle is required.
+ *
+ * In the "NON-VALID STATE" + "FAILURE STATE" we can clear the "FAILURE STATE"
+ * and recover the DryIce unit. By clearing the "NON-VALID STATE" as the last
+ * task, we bring back this unit into life.
+ */
+
+/*
+ * Do a write into the unit without interrupt support.
+ * We do not need to check the WEF here, because the only reason this kind of
+ * write error can happen is if we write to the unit twice within the 122 us
+ * interval. This cannot happen, since we are using this function only while
+ * setting up the unit.
+ */
+static void di_write_busy_wait(const struct imxdi_dev *imxdi, u32 val,
+			       unsigned reg)
+{
+	/* do the register write */
+	writel(val, imxdi->ioaddr + reg);
+
+	/*
+	 * now it takes four 32,768 kHz clock cycles to take
+	 * the change into effect = 122 us
+	 */
+	udelay(130);
+}
+
+static void di_what_is_to_be_done(struct imxdi_dev *imxdi,
+				  const char *power_supply)
+{
+	dev_emerg(imxdi->dev, "Please cycle the %s power supply in order to get the DryIce/RTC unit working again\n",
+		  power_supply);
+}
+
+static int di_handle_failure_state(struct imxdi_dev *imxdi, u32 dsr)
+{
+	u32 dcr;
+
+	dev_dbg(imxdi->dev, "DSR register reports: %08X\n", dsr);
+
+	dcr = readl(imxdi->ioaddr + DCR);
+
+	if (dcr & DCR_FSHL) {
+		/* we are out of luck */
+		di_what_is_to_be_done(imxdi, "battery");
+		return -ENODEV;
+	}
+	/*
+	 * with the next SYSTEM POR we will transit from the "FAILURE STATE"
+	 * into the "NON-VALID STATE" + "FAILURE STATE"
+	 */
+	di_what_is_to_be_done(imxdi, "main");
+
+	return -ENODEV;
+}
+
+static int di_handle_valid_state(struct imxdi_dev *imxdi, u32 dsr)
+{
+	/* initialize alarm */
+	di_write_busy_wait(imxdi, DCAMR_UNSET, DCAMR);
+	di_write_busy_wait(imxdi, 0, DCALR);
+
+	/* clear alarm flag */
+	if (dsr & DSR_CAF)
+		di_write_busy_wait(imxdi, DSR_CAF, DSR);
+
+	return 0;
+}
+
+static int di_handle_invalid_state(struct imxdi_dev *imxdi, u32 dsr)
+{
+	u32 dcr, sec;
+
+	/*
+	 * lets disable all sources which can force the DryIce unit into
+	 * the "FAILURE STATE" for now
+	 */
+	di_write_busy_wait(imxdi, 0x00000000, DTCR);
+	/* and lets protect them at runtime from any change */
+	di_write_busy_wait(imxdi, DCR_TDCSL, DCR);
+
+	sec = readl(imxdi->ioaddr + DTCMR);
+	if (sec != 0)
+		dev_warn(imxdi->dev,
+			 "The security violation has happened at %u seconds\n",
+			 sec);
+	/*
+	 * the timer cannot be set/modified if
+	 * - the TCHL or TCSL bit is set in DCR
+	 */
+	dcr = readl(imxdi->ioaddr + DCR);
+	if (!(dcr & DCR_TCE)) {
+		if (dcr & DCR_TCHL) {
+			/* we are out of luck */
+			di_what_is_to_be_done(imxdi, "battery");
+			return -ENODEV;
+		}
+		if (dcr & DCR_TCSL) {
+			di_what_is_to_be_done(imxdi, "main");
+			return -ENODEV;
+		}
+	}
+	/*
+	 * - the timer counter stops/is stopped if
+	 *   - its overflow flag is set (TCO in DSR)
+	 *      -> clear overflow bit to make it count again
+	 *   - NVF is set in DSR
+	 *      -> clear non-valid bit to make it count again
+	 *   - its TCE (DCR) is cleared
+	 *      -> set TCE to make it count
+	 *   - it was never set before
+	 *      -> write a time into it (required again if the NVF was set)
+	 */
+	/* state handled */
+	di_write_busy_wait(imxdi, DSR_NVF, DSR);
+	/* clear overflow flag */
+	di_write_busy_wait(imxdi, DSR_TCO, DSR);
+	/* enable the counter */
+	di_write_busy_wait(imxdi, dcr | DCR_TCE, DCR);
+	/* set and trigger it to make it count */
+	di_write_busy_wait(imxdi, sec, DTCMR);
+
+	/* now prepare for the valid state */
+	return di_handle_valid_state(imxdi, __raw_readl(imxdi->ioaddr + DSR));
+}
+
+static int di_handle_invalid_and_failure_state(struct imxdi_dev *imxdi, u32 dsr)
+{
+	u32 dcr;
+
+	/*
+	 * now we must first remove the tamper sources in order to get the
+	 * device out of the "FAILURE STATE"
+	 * To disable any of the following sources we need to modify the DTCR
+	 */
+	if (dsr & (DSR_WTD | DSR_ETBD | DSR_ETAD | DSR_EBD | DSR_SAD |
+			DSR_TTD | DSR_CTD | DSR_VTD | DSR_MCO | DSR_TCO)) {
+		dcr = __raw_readl(imxdi->ioaddr + DCR);
+		if (dcr & DCR_TDCHL) {
+			/*
+			 * the tamper register is locked. We cannot disable the
+			 * tamper detection. The TDCHL can only be reset by a
+			 * DRYICE POR, but we cannot force a DRYICE POR in
+			 * softwere because we are still in "FAILURE STATE".
+			 * We need a DRYICE POR via battery power cycling....
+			 */
+			/*
+			 * out of luck!
+			 * we cannot disable them without a DRYICE POR
+			 */
+			di_what_is_to_be_done(imxdi, "battery");
+			return -ENODEV;
+		}
+		if (dcr & DCR_TDCSL) {
+			/* a soft lock can be removed by a SYSTEM POR */
+			di_what_is_to_be_done(imxdi, "main");
+			return -ENODEV;
+		}
+	}
+
+	/* disable all sources */
+	di_write_busy_wait(imxdi, 0x00000000, DTCR);
+
+	/* clear the status bits now */
+	di_write_busy_wait(imxdi, dsr & (DSR_WTD | DSR_ETBD | DSR_ETAD |
+			DSR_EBD | DSR_SAD | DSR_TTD | DSR_CTD | DSR_VTD |
+			DSR_MCO | DSR_TCO), DSR);
+
+	dsr = readl(imxdi->ioaddr + DSR);
+	if ((dsr & ~(DSR_NVF | DSR_SVF | DSR_WBF | DSR_WNF |
+			DSR_WCF | DSR_WEF)) != 0)
+		dev_warn(imxdi->dev,
+			 "There are still some sources of pain in DSR: %08x!\n",
+			 dsr & ~(DSR_NVF | DSR_SVF | DSR_WBF | DSR_WNF |
+				 DSR_WCF | DSR_WEF));
+
+	/*
+	 * now we are trying to clear the "Security-violation flag" to
+	 * get the DryIce out of this state
+	 */
+	di_write_busy_wait(imxdi, DSR_SVF, DSR);
+
+	/* success? */
+	dsr = readl(imxdi->ioaddr + DSR);
+	if (dsr & DSR_SVF) {
+		dev_crit(imxdi->dev,
+			 "Cannot clear the security violation flag. We are ending up in an endless loop!\n");
+		/* last resort */
+		di_what_is_to_be_done(imxdi, "battery");
+		return -ENODEV;
+	}
+
+	/*
+	 * now we have left the "FAILURE STATE" and ending up in the
+	 * "NON-VALID STATE" time to recover everything
+	 */
+	return di_handle_invalid_state(imxdi, dsr);
+}
+
+static int di_handle_state(struct imxdi_dev *imxdi)
+{
+	int rc;
+	u32 dsr;
+
+	dsr = readl(imxdi->ioaddr + DSR);
+
+	switch (dsr & (DSR_NVF | DSR_SVF)) {
+	case DSR_NVF:
+		dev_warn(imxdi->dev, "Invalid stated unit detected\n");
+		rc = di_handle_invalid_state(imxdi, dsr);
+		break;
+	case DSR_SVF:
+		dev_warn(imxdi->dev, "Failure stated unit detected\n");
+		rc = di_handle_failure_state(imxdi, dsr);
+		break;
+	case DSR_NVF | DSR_SVF:
+		dev_warn(imxdi->dev,
+			 "Failure+Invalid stated unit detected\n");
+		rc = di_handle_invalid_and_failure_state(imxdi, dsr);
+		break;
+	default:
+		dev_notice(imxdi->dev, "Unlocked unit detected\n");
+		rc = di_handle_valid_state(imxdi, dsr);
+	}
+
+	return rc;
+}
+
+/*
+ * This function attempts to clear the dryice write-error flag.
+ *
+ * A dryice write error is similar to a bus fault and should not occur in
+ * normal operation.  Clearing the flag requires another write, so the root
+ * cause of the problem may need to be fixed before the flag can be cleared.
+ */
+static void clear_write_error(struct imxdi_dev *imxdi)
+{
+	int cnt;
+
+	dev_warn(imxdi->dev, "WARNING: Register write error!\n");
+
+	/* clear the write error flag */
+	writel(DSR_WEF, imxdi->ioaddr + DSR);
+
+	/* wait for it to take effect */
+	for (cnt = 0; cnt < 1000; cnt++) {
+		if ((readl(imxdi->ioaddr + DSR) & DSR_WEF) == 0)
+			return;
+		udelay(10);
+	}
+	dev_err(imxdi->dev,
+			"ERROR: Cannot clear write-error flag!\n");
+}
+
+/*
+ * Write a dryice register and wait until it completes.
+ *
+ * This function uses interrupts to determine when the
+ * write has completed.
+ */
+static int di_write_wait(struct imxdi_dev *imxdi, u32 val, int reg)
+{
+	int rc = 0;
+	uint32_t dsr;
+	uint64_t start;
+
+	/* do the register write */
+	writel(val, imxdi->ioaddr + reg);
+
+	start = get_time_ns();
+
+	/* wait for the write to finish */
+	while (1) {
+		dsr = readl(imxdi->ioaddr + DSR);
+
+		if (dsr & (DSR_WCF | DSR_WEF))
+			break;
+		if (is_timeout(start, MSECOND))
+			return -EIO;
+	}
+
+	/* check for write error */
+	if (dsr & DSR_WEF) {
+		clear_write_error(imxdi);
+		rc = -EIO;
+	}
+
+	return rc;
+}
+
+static struct imxdi_dev *to_imxdi_dev(struct rtc_device *rtc)
+{
+	return container_of(rtc, struct imxdi_dev, rtc);
+}
+
+/*
+ * read the seconds portion of the current time from the dryice time counter
+ */
+static int dryice_rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
+{
+	struct imxdi_dev *imxdi = to_imxdi_dev(rtc);
+	unsigned long now;
+
+	now = readl(imxdi->ioaddr + DTCMR);
+	rtc_time_to_tm(now, tm);
+
+	return 0;
+}
+
+/*
+ * set the seconds portion of dryice time counter and clear the
+ * fractional part.
+ */
+static int dryice_rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
+{
+	struct imxdi_dev *imxdi = to_imxdi_dev(rtc);
+	u32 dcr, dsr;
+	int ret;
+	unsigned long secs;
+
+	ret = rtc_tm_to_time(tm, &secs);
+	if (ret)
+		return ret;
+
+	dcr = readl(imxdi->ioaddr + DCR);
+	dsr = readl(imxdi->ioaddr + DSR);
+
+	if (!(dcr & DCR_TCE) || (dsr & DSR_SVF)) {
+		if (dcr & DCR_TCHL) {
+			/* we are even more out of luck */
+			di_what_is_to_be_done(imxdi, "battery");
+			return -EPERM;
+		}
+		if ((dcr & DCR_TCSL) || (dsr & DSR_SVF)) {
+			/* we are out of luck for now */
+			di_what_is_to_be_done(imxdi, "main");
+			return -EPERM;
+		}
+	}
+
+	/* zero the fractional part first */
+	ret = di_write_wait(imxdi, 0, DTCLR);
+	if (ret)
+		return ret;
+
+	ret = di_write_wait(imxdi, secs, DTCMR);
+	if (ret)
+		return ret;
+
+	return di_write_wait(imxdi, readl(imxdi->ioaddr + DCR) | DCR_TCE, DCR);
+}
+
+static const struct rtc_class_ops dryice_rtc_ops = {
+	.read_time = dryice_rtc_read_time,
+	.set_time = dryice_rtc_set_time,
+};
+
+static int nvstore_write(struct device_d *dev, const int reg, const void *val,
+			 int bytes)
+{
+	struct imxdi_dev *imxdi = dev->parent->priv;
+	const u32 *val32 = val;
+
+	if (bytes != 4)
+		return 0;
+
+	writel(*val32, imxdi->ioaddr + DGPR);
+
+	return 0;
+}
+
+static int nvstore_read(struct device_d *dev, const int reg, void *val,
+			int bytes)
+{
+	struct imxdi_dev *imxdi = dev->parent->priv;
+	u32 *val32 = val;
+
+	if (bytes != 4)
+		return 0;
+
+	*val32 = readl(imxdi->ioaddr + DGPR);
+
+	return 0;
+}
+
+static struct nvmem_bus nvstore_nvmem_bus = {
+	.write = nvstore_write,
+	.read  = nvstore_read,
+};
+
+static struct nvmem_config nvstore_nvmem_config = {
+	.name = "nvstore",
+	.stride = 4,
+	.word_size = 4,
+	.size = 4,
+	.bus = &nvstore_nvmem_bus,
+};
+
+static int __init dryice_rtc_probe(struct device_d *dev)
+{
+	struct resource *res;
+	struct imxdi_dev *imxdi;
+	int ret;
+
+	imxdi = xzalloc(sizeof(*imxdi));
+
+	imxdi->dev = dev;
+	imxdi->rtc.ops = &dryice_rtc_ops;
+
+	res = dev_request_mem_resource(dev, 0);
+	if (IS_ERR(res))
+		return PTR_ERR(res);
+
+	imxdi->ioaddr = IOMEM(res->start);
+
+	imxdi->clk = clk_get(dev, NULL);
+	if (IS_ERR(imxdi->clk))
+		return PTR_ERR(imxdi->clk);
+
+	ret = clk_enable(imxdi->clk);
+	if (ret)
+		return ret;
+
+	/*
+	 * Initialize dryice hardware
+	 */
+
+	/* mask all interrupts */
+	writel(0, imxdi->ioaddr + DIER);
+
+	ret = di_handle_state(imxdi);
+	if (ret)
+		goto err;
+
+	dev->priv = imxdi;
+
+	nvstore_nvmem_config.dev = dev;
+
+	imxdi->nvmem = nvmem_register(&nvstore_nvmem_config);
+	if (IS_ENABLED(CONFIG_NVMEM) && IS_ERR(imxdi->nvmem)) {
+		ret = PTR_ERR(imxdi->nvmem);
+		goto err;
+	}
+
+	ret = rtc_register(&imxdi->rtc);
+	if (ret)
+		goto err;
+
+	return 0;
+
+err:
+	clk_disable(imxdi->clk);
+
+	return ret;
+}
+
+static __maybe_unused const struct of_device_id dryice_dt_ids[] = {
+	{ .compatible = "fsl,imx25-rtc" },
+	{ /* sentinel */ }
+};
+
+static struct driver_d dryice_rtc_driver = {
+        .name   = "imx-di-rtc",
+        .probe  = dryice_rtc_probe,
+        .of_compatible = DRV_OF_COMPAT(dryice_dt_ids),
+};
+device_platform_driver(dryice_rtc_driver);
-- 
2.20.1


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