drivers/rtc/rtc-isl12026.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * An I2C driver for the Intersil ISL 12026
  *
  * Copyright (c) 2018 Cavium, Inc.
  */
 #include <linux/bcd.h>
 #include <linux/delay.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/nvmem-provider.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>

 /* register offsets */
 #define ISL12026_REG_PWR	0x14
 # define ISL12026_REG_PWR_BSW	BIT(6)
 # define ISL12026_REG_PWR_SBIB	BIT(7)
 #define ISL12026_REG_SC		0x30
 #define ISL12026_REG_HR		0x32
 # define ISL12026_REG_HR_MIL	BIT(7)	/* military or 24 hour time */
 #define ISL12026_REG_SR		0x3f
 # define ISL12026_REG_SR_RTCF	BIT(0)
 # define ISL12026_REG_SR_WEL	BIT(1)
 # define ISL12026_REG_SR_RWEL	BIT(2)
 # define ISL12026_REG_SR_MBZ	BIT(3)
 # define ISL12026_REG_SR_OSCF	BIT(4)

 /* The EEPROM array responds at i2c address 0x57 */
 #define ISL12026_EEPROM_ADDR	0x57

 #define ISL12026_PAGESIZE 16
 #define ISL12026_NVMEM_WRITE_TIME 20

 struct isl12026 {
 	struct rtc_device *rtc;
 	struct i2c_client *nvm_client;
 };

 static int isl12026_read_reg(struct i2c_client *client, int reg)
 {
 	u8 addr[] = {0, reg};
 	u8 val;
 	int ret;

 	struct i2c_msg msgs[] = {
 		{
 			.addr	= client->addr,
 			.flags	= 0,
 			.len	= sizeof(addr),
 			.buf	= addr
 		}, {
 			.addr	= client->addr,
 			.flags	= I2C_M_RD,
 			.len	= 1,
 			.buf	= &val
 		}
 	};

 	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 	if (ret != ARRAY_SIZE(msgs)) {
 		dev_err(&client->dev, "read reg error, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 	} else {
 		ret = val;
 	}

 	return ret;
 }

 static int isl12026_arm_write(struct i2c_client *client)
 {
 	int ret;
 	u8 op[3];
 	struct i2c_msg msg = {
 		.addr	= client->addr,
 		.flags	= 0,
 		.len	= 1,
 		.buf	= op
 	};

 	/* Set SR.WEL */
 	op[0] = 0;
 	op[1] = ISL12026_REG_SR;
 	op[2] = ISL12026_REG_SR_WEL;
 	msg.len = 3;
 	ret = i2c_transfer(client->adapter, &msg, 1);
 	if (ret != 1) {
 		dev_err(&client->dev, "write error SR.WEL, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	}

 	/* Set SR.WEL and SR.RWEL */
 	op[2] = ISL12026_REG_SR_WEL | ISL12026_REG_SR_RWEL;
 	msg.len = 3;
 	ret = i2c_transfer(client->adapter, &msg, 1);
 	if (ret != 1) {
 		dev_err(&client->dev,
 			"write error SR.WEL|SR.RWEL, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	} else {
 		ret = 0;
 	}
 out:
 	return ret;
 }

 static int isl12026_disarm_write(struct i2c_client *client)
 {
 	int ret;
 	u8 op[3] = {0, ISL12026_REG_SR, 0};
 	struct i2c_msg msg = {
 		.addr	= client->addr,
 		.flags	= 0,
 		.len	= sizeof(op),
 		.buf	= op
 	};

 	ret = i2c_transfer(client->adapter, &msg, 1);
 	if (ret != 1) {
 		dev_err(&client->dev,
 			"write error SR, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 	} else {
 		ret = 0;
 	}

 	return ret;
 }

 static int isl12026_write_reg(struct i2c_client *client, int reg, u8 val)
 {
 	int ret;
 	u8 op[3] = {0, reg, val};
 	struct i2c_msg msg = {
 		.addr	= client->addr,
 		.flags	= 0,
 		.len	= sizeof(op),
 		.buf	= op
 	};

 	ret = isl12026_arm_write(client);
 	if (ret)
 		return ret;

 	ret = i2c_transfer(client->adapter, &msg, 1);
 	if (ret != 1) {
 		dev_err(&client->dev, "write error CCR, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	}

 	msleep(ISL12026_NVMEM_WRITE_TIME);

 	ret = isl12026_disarm_write(client);
 out:
 	return ret;
 }

 static int isl12026_rtc_set_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	int ret;
 	u8 op[10];
 	struct i2c_msg msg = {
 		.addr	= client->addr,
 		.flags	= 0,
 		.len	= sizeof(op),
 		.buf	= op
 	};

 	ret = isl12026_arm_write(client);
 	if (ret)
 		return ret;

 	/* Set the CCR registers */
 	op[0] = 0;
 	op[1] = ISL12026_REG_SC;
 	op[2] = bin2bcd(tm->tm_sec); /* SC */
 	op[3] = bin2bcd(tm->tm_min); /* MN */
 	op[4] = bin2bcd(tm->tm_hour) | ISL12026_REG_HR_MIL; /* HR */
 	op[5] = bin2bcd(tm->tm_mday); /* DT */
 	op[6] = bin2bcd(tm->tm_mon + 1); /* MO */
 	op[7] = bin2bcd(tm->tm_year % 100); /* YR */
 	op[8] = bin2bcd(tm->tm_wday & 7); /* DW */
 	op[9] = bin2bcd(tm->tm_year >= 100 ? 20 : 19); /* Y2K */
 	ret = i2c_transfer(client->adapter, &msg, 1);
 	if (ret != 1) {
 		dev_err(&client->dev, "write error CCR, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	}

 	ret = isl12026_disarm_write(client);
 out:
 	return ret;
 }

 static int isl12026_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	u8 ccr[8];
 	u8 addr[2];
 	u8 sr;
 	int ret;
 	struct i2c_msg msgs[] = {
 		{
 			.addr	= client->addr,
 			.flags	= 0,
 			.len	= sizeof(addr),
 			.buf	= addr
 		}, {
 			.addr	= client->addr,
 			.flags	= I2C_M_RD,
 		}
 	};

 	/* First, read SR */
 	addr[0] = 0;
 	addr[1] = ISL12026_REG_SR;
 	msgs[1].len = 1;
 	msgs[1].buf = &sr;

 	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 	if (ret != ARRAY_SIZE(msgs)) {
 		dev_err(&client->dev, "read error, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	}

 	if (sr & ISL12026_REG_SR_RTCF)
 		dev_warn(&client->dev, "Real-Time Clock Failure on read\n");
 	if (sr & ISL12026_REG_SR_OSCF)
 		dev_warn(&client->dev, "Oscillator Failure on read\n");

 	/* Second, CCR regs */
 	addr[0] = 0;
 	addr[1] = ISL12026_REG_SC;
 	msgs[1].len = sizeof(ccr);
 	msgs[1].buf = ccr;

 	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 	if (ret != ARRAY_SIZE(msgs)) {
 		dev_err(&client->dev, "read error, ret=%d\n", ret);
 		ret = ret < 0 ? ret : -EIO;
 		goto out;
 	}

 	tm->tm_sec = bcd2bin(ccr[0] & 0x7F);
 	tm->tm_min = bcd2bin(ccr[1] & 0x7F);
 	if (ccr[2] & ISL12026_REG_HR_MIL)
 		tm->tm_hour = bcd2bin(ccr[2] & 0x3F);
 	else
 		tm->tm_hour = bcd2bin(ccr[2] & 0x1F) +
 			((ccr[2] & 0x20) ? 12 : 0);
 	tm->tm_mday = bcd2bin(ccr[3] & 0x3F);
 	tm->tm_mon = bcd2bin(ccr[4] & 0x1F) - 1;
 	tm->tm_year = bcd2bin(ccr[5]);
 	if (bcd2bin(ccr[7]) == 20)
 		tm->tm_year += 100;
 	tm->tm_wday = ccr[6] & 0x07;

 	ret = 0;
 out:
 	return ret;
 }

 static const struct rtc_class_ops isl12026_rtc_ops = {
 	.read_time	= isl12026_rtc_read_time,
 	.set_time	= isl12026_rtc_set_time,
 };

 static int isl12026_nvm_read(void *p, unsigned int offset,
 			     void *val, size_t bytes)
 {
 	struct isl12026 *priv = p;
 	int ret;
 	u8 addr[2];
 	struct i2c_msg msgs[] = {
 		{
 			.addr	= priv->nvm_client->addr,
 			.flags	= 0,
 			.len	= sizeof(addr),
 			.buf	= addr
 		}, {
 			.addr	= priv->nvm_client->addr,
 			.flags	= I2C_M_RD,
 			.buf	= val
 		}
 	};

 	/*
 	 * offset and bytes checked and limited by nvmem core, so
 	 * proceed without further checks.
 	 */
 	ret = mutex_lock_interruptible(&priv->rtc->ops_lock);
 	if (ret)
 		return ret;

 	/* 2 bytes of address, most significant first */
 	addr[0] = offset >> 8;
 	addr[1] = offset;
 	msgs[1].len = bytes;
 	ret = i2c_transfer(priv->nvm_client->adapter, msgs, ARRAY_SIZE(msgs));

 	mutex_unlock(&priv->rtc->ops_lock);

 	if (ret != ARRAY_SIZE(msgs)) {
 		dev_err(&priv->nvm_client->dev,
 			"nvmem read error, ret=%d\n", ret);
 		return ret < 0 ? ret : -EIO;
 	}

 	return 0;
 }

 static int isl12026_nvm_write(void *p, unsigned int offset,
 			      void *val, size_t bytes)
 {
 	struct isl12026 *priv = p;
 	int ret;
 	u8 *v = val;
 	size_t chunk_size, num_written;
 	u8 payload[ISL12026_PAGESIZE + 2]; /* page + 2 address bytes */
 	struct i2c_msg msgs[] = {
 		{
 			.addr	= priv->nvm_client->addr,
 			.flags	= 0,
 			.buf	= payload
 		}
 	};

 	/*
 	 * offset and bytes checked and limited by nvmem core, so
 	 * proceed without further checks.
 	 */
 	ret = mutex_lock_interruptible(&priv->rtc->ops_lock);
 	if (ret)
 		return ret;

 	num_written = 0;
 	while (bytes) {
 		chunk_size = round_down(offset, ISL12026_PAGESIZE) +
 			ISL12026_PAGESIZE - offset;
 		chunk_size = min(bytes, chunk_size);
 		/*
 		 * 2 bytes of address, most significant first, followed
 		 * by page data bytes
 		 */
 		memcpy(payload + 2, v + num_written, chunk_size);
 		payload[0] = offset >> 8;
 		payload[1] = offset;
 		msgs[0].len = chunk_size + 2;
 		ret = i2c_transfer(priv->nvm_client->adapter,
 				   msgs, ARRAY_SIZE(msgs));
 		if (ret != ARRAY_SIZE(msgs)) {
 			dev_err(&priv->nvm_client->dev,
 				"nvmem write error, ret=%d\n", ret);
 			ret = ret < 0 ? ret : -EIO;
 			break;
 		}
 		ret = 0;
 		bytes -= chunk_size;
 		offset += chunk_size;
 		num_written += chunk_size;
 		msleep(ISL12026_NVMEM_WRITE_TIME);
 	}

 	mutex_unlock(&priv->rtc->ops_lock);

 	return ret;
 }

 static void isl12026_force_power_modes(struct i2c_client *client)
 {
 	int ret;
 	int pwr, requested_pwr;
 	u32 bsw_val, sbib_val;
 	bool set_bsw, set_sbib;

 	/*
 	 * If we can read the of_property, set the specified value.
 	 * If there is an error reading the of_property (likely
 	 * because it does not exist), keep the current value.
 	 */
 	ret = of_property_read_u32(client->dev.of_node,
 				   "isil,pwr-bsw", &bsw_val);
 	set_bsw = (ret == 0);

 	ret = of_property_read_u32(client->dev.of_node,
 				   "isil,pwr-sbib", &sbib_val);
 	set_sbib = (ret == 0);

 	/* Check if PWR.BSW and/or PWR.SBIB need specified values */
 	if (!set_bsw && !set_sbib)
 		return;

 	pwr = isl12026_read_reg(client, ISL12026_REG_PWR);
 	if (pwr < 0) {
 		dev_warn(&client->dev, "Error: Failed to read PWR %d\n", pwr);
 		return;
 	}

 	requested_pwr = pwr;

 	if (set_bsw) {
 		if (bsw_val)
 			requested_pwr |= ISL12026_REG_PWR_BSW;
 		else
 			requested_pwr &= ~ISL12026_REG_PWR_BSW;
 	} /* else keep current BSW */

 	if (set_sbib) {
 		if (sbib_val)
 			requested_pwr |= ISL12026_REG_PWR_SBIB;
 		else
 			requested_pwr &= ~ISL12026_REG_PWR_SBIB;
 	} /* else keep current SBIB */

 	if (pwr >= 0 && pwr != requested_pwr) {
 		dev_dbg(&client->dev, "PWR: %02x\n", pwr);
 		dev_dbg(&client->dev, "Updating PWR to: %02x\n", requested_pwr);
 		isl12026_write_reg(client, ISL12026_REG_PWR, requested_pwr);
 	}
 }

 static int isl12026_probe_new(struct i2c_client *client)
 {
 	struct isl12026 *priv;
 	int ret;
 	struct nvmem_config nvm_cfg = {
 		.name = "isl12026-",
 		.base_dev = &client->dev,
 		.stride = 1,
 		.word_size = 1,
 		.size = 512,
 		.reg_read = isl12026_nvm_read,
 		.reg_write = isl12026_nvm_write,
 	};

 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
 		return -ENODEV;

 	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	i2c_set_clientdata(client, priv);

 	isl12026_force_power_modes(client);

 	priv->nvm_client = i2c_new_dummy(client->adapter, ISL12026_EEPROM_ADDR);
 	if (!priv->nvm_client)
 		return -ENOMEM;

 	priv->rtc = devm_rtc_allocate_device(&client->dev);
 	ret = PTR_ERR_OR_ZERO(priv->rtc);
 	if (ret)
 		return ret;

 	priv->rtc->ops = &isl12026_rtc_ops;
 	nvm_cfg.priv = priv;
 	ret = rtc_nvmem_register(priv->rtc, &nvm_cfg);
 	if (ret)
 		return ret;

 	return rtc_register_device(priv->rtc);
 }

 static int isl12026_remove(struct i2c_client *client)
 {
 	struct isl12026 *priv = i2c_get_clientdata(client);

 	i2c_unregister_device(priv->nvm_client);
 	return 0;
 }

 static const struct of_device_id isl12026_dt_match[] = {
 	{ .compatible = "isil,isl12026" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, isl12026_dt_match);

 static struct i2c_driver isl12026_driver = {
 	.driver		= {
 		.name	= "rtc-isl12026",
 		.of_match_table = isl12026_dt_match,
 	},
 	.probe_new	= isl12026_probe_new,
 	.remove		= isl12026_remove,
 };

 module_i2c_driver(isl12026_driver);

 MODULE_DESCRIPTION("ISL 12026 RTC driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* An I2C driver for the Intersil ISL 12026
	*
	* Copyright (c) 2018 Cavium, Inc.
	*/
	#include <linux/bcd.h>
	#include <linux/delay.h>
	#include <linux/i2c.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/nvmem-provider.h>
	#include <linux/of.h>
	#include <linux/of_device.h>
	#include <linux/rtc.h>
	#include <linux/slab.h>

	/* register offsets */
	#define ISL12026_REG_PWR 0x14
	# define ISL12026_REG_PWR_BSW BIT(6)
	# define ISL12026_REG_PWR_SBIB BIT(7)
	#define ISL12026_REG_SC 0x30
	#define ISL12026_REG_HR 0x32
	# define ISL12026_REG_HR_MIL BIT(7) /* military or 24 hour time */
	#define ISL12026_REG_SR 0x3f
	# define ISL12026_REG_SR_RTCF BIT(0)
	# define ISL12026_REG_SR_WEL BIT(1)
	# define ISL12026_REG_SR_RWEL BIT(2)
	# define ISL12026_REG_SR_MBZ BIT(3)
	# define ISL12026_REG_SR_OSCF BIT(4)

	/* The EEPROM array responds at i2c address 0x57 */
	#define ISL12026_EEPROM_ADDR 0x57

	#define ISL12026_PAGESIZE 16
	#define ISL12026_NVMEM_WRITE_TIME 20

	struct isl12026 {
	struct rtc_device *rtc;
	struct i2c_client *nvm_client;
	};

	static int isl12026_read_reg(struct i2c_client *client, int reg)
	{
	u8 addr[] = {0, reg};
	u8 val;
	int ret;

	struct i2c_msg msgs[] = {
	{
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(addr),
	.buf = addr
	}, {
	.addr = client->addr,
	.flags = I2C_M_RD,
	.len = 1,
	.buf = &val
	}
	};

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret != ARRAY_SIZE(msgs)) {
	dev_err(&client->dev, "read reg error, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	} else {
	ret = val;
	}

	return ret;
	}

	static int isl12026_arm_write(struct i2c_client *client)
	{
	int ret;
	u8 op[3];
	struct i2c_msg msg = {
	.addr = client->addr,
	.flags = 0,
	.len = 1,
	.buf = op
	};

	/* Set SR.WEL */
	op[0] = 0;
	op[1] = ISL12026_REG_SR;
	op[2] = ISL12026_REG_SR_WEL;
	msg.len = 3;
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret != 1) {
	dev_err(&client->dev, "write error SR.WEL, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	}

	/* Set SR.WEL and SR.RWEL */
	op[2] = ISL12026_REG_SR_WEL \| ISL12026_REG_SR_RWEL;
	msg.len = 3;
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret != 1) {
	dev_err(&client->dev,
	"write error SR.WEL\|SR.RWEL, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	} else {
	ret = 0;
	}
	out:
	return ret;
	}

	static int isl12026_disarm_write(struct i2c_client *client)
	{
	int ret;
	u8 op[3] = {0, ISL12026_REG_SR, 0};
	struct i2c_msg msg = {
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(op),
	.buf = op
	};

	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret != 1) {
	dev_err(&client->dev,
	"write error SR, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	} else {
	ret = 0;
	}

	return ret;
	}

	static int isl12026_write_reg(struct i2c_client *client, int reg, u8 val)
	{
	int ret;
	u8 op[3] = {0, reg, val};
	struct i2c_msg msg = {
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(op),
	.buf = op
	};

	ret = isl12026_arm_write(client);
	if (ret)
	return ret;

	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret != 1) {
	dev_err(&client->dev, "write error CCR, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	}

	msleep(ISL12026_NVMEM_WRITE_TIME);

	ret = isl12026_disarm_write(client);
	out:
	return ret;
	}

	static int isl12026_rtc_set_time(struct device dev, struct rtc_time tm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	int ret;
	u8 op[10];
	struct i2c_msg msg = {
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(op),
	.buf = op
	};

	ret = isl12026_arm_write(client);
	if (ret)
	return ret;

	/* Set the CCR registers */
	op[0] = 0;
	op[1] = ISL12026_REG_SC;
	op[2] = bin2bcd(tm->tm_sec); /* SC */
	op[3] = bin2bcd(tm->tm_min); /* MN */
	op[4] = bin2bcd(tm->tm_hour) \| ISL12026_REG_HR_MIL; /* HR */
	op[5] = bin2bcd(tm->tm_mday); /* DT */
	op[6] = bin2bcd(tm->tm_mon + 1); /* MO */
	op[7] = bin2bcd(tm->tm_year % 100); /* YR */
	op[8] = bin2bcd(tm->tm_wday & 7); /* DW */
	op[9] = bin2bcd(tm->tm_year >= 100 ? 20 : 19); /* Y2K */
	ret = i2c_transfer(client->adapter, &msg, 1);
	if (ret != 1) {
	dev_err(&client->dev, "write error CCR, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	}

	ret = isl12026_disarm_write(client);
	out:
	return ret;
	}

	static int isl12026_rtc_read_time(struct device dev, struct rtc_time tm)
	{
	struct i2c_client *client = to_i2c_client(dev);
	u8 ccr[8];
	u8 addr[2];
	u8 sr;
	int ret;
	struct i2c_msg msgs[] = {
	{
	.addr = client->addr,
	.flags = 0,
	.len = sizeof(addr),
	.buf = addr
	}, {
	.addr = client->addr,
	.flags = I2C_M_RD,
	}
	};

	/* First, read SR */
	addr[0] = 0;
	addr[1] = ISL12026_REG_SR;
	msgs[1].len = 1;
	msgs[1].buf = &sr;

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret != ARRAY_SIZE(msgs)) {
	dev_err(&client->dev, "read error, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	}

	if (sr & ISL12026_REG_SR_RTCF)
	dev_warn(&client->dev, "Real-Time Clock Failure on read\n");
	if (sr & ISL12026_REG_SR_OSCF)
	dev_warn(&client->dev, "Oscillator Failure on read\n");

	/* Second, CCR regs */
	addr[0] = 0;
	addr[1] = ISL12026_REG_SC;
	msgs[1].len = sizeof(ccr);
	msgs[1].buf = ccr;

	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (ret != ARRAY_SIZE(msgs)) {
	dev_err(&client->dev, "read error, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	goto out;
	}

	tm->tm_sec = bcd2bin(ccr[0] & 0x7F);
	tm->tm_min = bcd2bin(ccr[1] & 0x7F);
	if (ccr[2] & ISL12026_REG_HR_MIL)
	tm->tm_hour = bcd2bin(ccr[2] & 0x3F);
	else
	tm->tm_hour = bcd2bin(ccr[2] & 0x1F) +
	((ccr[2] & 0x20) ? 12 : 0);
	tm->tm_mday = bcd2bin(ccr[3] & 0x3F);
	tm->tm_mon = bcd2bin(ccr[4] & 0x1F) - 1;
	tm->tm_year = bcd2bin(ccr[5]);
	if (bcd2bin(ccr[7]) == 20)
	tm->tm_year += 100;
	tm->tm_wday = ccr[6] & 0x07;

	ret = 0;
	out:
	return ret;
	}

	static const struct rtc_class_ops isl12026_rtc_ops = {
	.read_time = isl12026_rtc_read_time,
	.set_time = isl12026_rtc_set_time,
	};

	static int isl12026_nvm_read(void *p, unsigned int offset,
	void *val, size_t bytes)
	{
	struct isl12026 *priv = p;
	int ret;
	u8 addr[2];
	struct i2c_msg msgs[] = {
	{
	.addr = priv->nvm_client->addr,
	.flags = 0,
	.len = sizeof(addr),
	.buf = addr
	}, {
	.addr = priv->nvm_client->addr,
	.flags = I2C_M_RD,
	.buf = val
	}
	};

	/*
	* offset and bytes checked and limited by nvmem core, so
	* proceed without further checks.
	*/
	ret = mutex_lock_interruptible(&priv->rtc->ops_lock);
	if (ret)
	return ret;

	/* 2 bytes of address, most significant first */
	addr[0] = offset >> 8;
	addr[1] = offset;
	msgs[1].len = bytes;
	ret = i2c_transfer(priv->nvm_client->adapter, msgs, ARRAY_SIZE(msgs));

	mutex_unlock(&priv->rtc->ops_lock);

	if (ret != ARRAY_SIZE(msgs)) {
	dev_err(&priv->nvm_client->dev,
	"nvmem read error, ret=%d\n", ret);
	return ret < 0 ? ret : -EIO;
	}

	return 0;
	}

	static int isl12026_nvm_write(void *p, unsigned int offset,
	void *val, size_t bytes)
	{
	struct isl12026 *priv = p;
	int ret;
	u8 *v = val;
	size_t chunk_size, num_written;
	u8 payload[ISL12026_PAGESIZE + 2]; /* page + 2 address bytes */
	struct i2c_msg msgs[] = {
	{
	.addr = priv->nvm_client->addr,
	.flags = 0,
	.buf = payload
	}
	};

	/*
	* offset and bytes checked and limited by nvmem core, so
	* proceed without further checks.
	*/
	ret = mutex_lock_interruptible(&priv->rtc->ops_lock);
	if (ret)
	return ret;

	num_written = 0;
	while (bytes) {
	chunk_size = round_down(offset, ISL12026_PAGESIZE) +
	ISL12026_PAGESIZE - offset;
	chunk_size = min(bytes, chunk_size);
	/*
	* 2 bytes of address, most significant first, followed
	* by page data bytes
	*/
	memcpy(payload + 2, v + num_written, chunk_size);
	payload[0] = offset >> 8;
	payload[1] = offset;
	msgs[0].len = chunk_size + 2;
	ret = i2c_transfer(priv->nvm_client->adapter,
	msgs, ARRAY_SIZE(msgs));
	if (ret != ARRAY_SIZE(msgs)) {
	dev_err(&priv->nvm_client->dev,
	"nvmem write error, ret=%d\n", ret);
	ret = ret < 0 ? ret : -EIO;
	break;
	}
	ret = 0;
	bytes -= chunk_size;
	offset += chunk_size;
	num_written += chunk_size;
	msleep(ISL12026_NVMEM_WRITE_TIME);
	}

	mutex_unlock(&priv->rtc->ops_lock);

	return ret;
	}

	static void isl12026_force_power_modes(struct i2c_client *client)
	{
	int ret;
	int pwr, requested_pwr;
	u32 bsw_val, sbib_val;
	bool set_bsw, set_sbib;

	/*
	* If we can read the of_property, set the specified value.
	* If there is an error reading the of_property (likely
	* because it does not exist), keep the current value.
	*/
	ret = of_property_read_u32(client->dev.of_node,
	"isil,pwr-bsw", &bsw_val);
	set_bsw = (ret == 0);

	ret = of_property_read_u32(client->dev.of_node,
	"isil,pwr-sbib", &sbib_val);
	set_sbib = (ret == 0);

	/* Check if PWR.BSW and/or PWR.SBIB need specified values */
	if (!set_bsw && !set_sbib)
	return;

	pwr = isl12026_read_reg(client, ISL12026_REG_PWR);
	if (pwr < 0) {
	dev_warn(&client->dev, "Error: Failed to read PWR %d\n", pwr);
	return;
	}

	requested_pwr = pwr;

	if (set_bsw) {
	if (bsw_val)
	requested_pwr \|= ISL12026_REG_PWR_BSW;
	else
	requested_pwr &= ~ISL12026_REG_PWR_BSW;
	} /* else keep current BSW */

	if (set_sbib) {
	if (sbib_val)
	requested_pwr \|= ISL12026_REG_PWR_SBIB;
	else
	requested_pwr &= ~ISL12026_REG_PWR_SBIB;
	} /* else keep current SBIB */

	if (pwr >= 0 && pwr != requested_pwr) {
	dev_dbg(&client->dev, "PWR: %02x\n", pwr);
	dev_dbg(&client->dev, "Updating PWR to: %02x\n", requested_pwr);
	isl12026_write_reg(client, ISL12026_REG_PWR, requested_pwr);
	}
	}

	static int isl12026_probe_new(struct i2c_client *client)
	{
	struct isl12026 *priv;
	int ret;
	struct nvmem_config nvm_cfg = {
	.name = "isl12026-",
	.base_dev = &client->dev,
	.stride = 1,
	.word_size = 1,
	.size = 512,
	.reg_read = isl12026_nvm_read,
	.reg_write = isl12026_nvm_write,
	};

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
	return -ENODEV;

	priv = devm_kzalloc(&client->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	i2c_set_clientdata(client, priv);

	isl12026_force_power_modes(client);

	priv->nvm_client = i2c_new_dummy(client->adapter, ISL12026_EEPROM_ADDR);
	if (!priv->nvm_client)
	return -ENOMEM;

	priv->rtc = devm_rtc_allocate_device(&client->dev);
	ret = PTR_ERR_OR_ZERO(priv->rtc);
	if (ret)
	return ret;

	priv->rtc->ops = &isl12026_rtc_ops;
	nvm_cfg.priv = priv;
	ret = rtc_nvmem_register(priv->rtc, &nvm_cfg);
	if (ret)
	return ret;

	return rtc_register_device(priv->rtc);
	}

	static int isl12026_remove(struct i2c_client *client)
	{
	struct isl12026 *priv = i2c_get_clientdata(client);

	i2c_unregister_device(priv->nvm_client);
	return 0;
	}

	static const struct of_device_id isl12026_dt_match[] = {
	{ .compatible = "isil,isl12026" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, isl12026_dt_match);

	static struct i2c_driver isl12026_driver = {
	.driver = {
	.name = "rtc-isl12026",
	.of_match_table = isl12026_dt_match,
	},
	.probe_new = isl12026_probe_new,
	.remove = isl12026_remove,
	};

	module_i2c_driver(isl12026_driver);

	MODULE_DESCRIPTION("ISL 12026 RTC driver");
	MODULE_LICENSE("GPL");