@@ -7,6 +7,8 @@
  * This file is subject to the terms and conditions of the GNU General Public
  * License version 2. See the file "COPYING" in the main directory of
  * this archive for more details.
+ *
+ * Datasheet: https://datasheets.maximintegrated.com/en/ds/DS1302.pdf
  */
 
 #include <linux/bcd.h>

@@ -39,27 +41,61 @@
 #define	RTC_ADDR_MIN	0x01		/* Address of minute register */
 #define	RTC_ADDR_SEC	0x00		/* Address of second register */
 
+struct ds1302 {
+	const struct ds1302_ops *ops;
+	struct device *dev;
+};
+
+struct ds1302_ops {
+	int (*read)(struct ds1302 *, u8, u8 *, int);
+	int (*write)(struct ds1302 *, u8, const u8 *, int);
+};
+
+static int ds1302_readbyte(struct ds1302 *ds1302, u8 addr)
+{
+	u8 val;
+	int err;
+
+	err = ds1302->ops->read(ds1302, addr, &val, 1);
+
+	return err ? err : val;
+}
+
+static int ds1302_writebyte(struct ds1302 *ds1302, u8 addr, u8 val)
+{
+	return ds1302->ops->write(ds1302, addr, &val, 1);
+}
+
+static int ds1302_readburst(struct ds1302 *ds1302, u8 addr, u8 *buf, int size)
+{
+	if (addr != RTC_CLCK_BURST)
+		return -EINVAL;
+
+	return ds1302->ops->read(ds1302, addr, buf, size);
+}
+
+static int ds1302_writeburst(struct ds1302 *ds1302, u8 addr, const u8 *buf,
+			     int size)
+{
+	if (addr != RTC_CLCK_BURST)
+		return -EINVAL;
+
+	return ds1302->ops->write(ds1302, addr, buf, size);
+}
+
 static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
 {
-	struct spi_device	*spi = dev_get_drvdata(dev);
-	u8		buf[1 + RTC_CLCK_LEN];
+	struct ds1302	*ds1302 = dev_get_drvdata(dev);
+	u8		buf[RTC_CLCK_LEN];
 	u8		*bp = buf;
 	int		status;
 
 	/* Enable writing */
-	bp = buf;
-	*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
-	*bp++ = RTC_CMD_WRITE_ENABLE;
-
-	status = spi_write_then_read(spi, buf, 2,
-			NULL, 0);
+	status = ds1302_writebyte(ds1302, RTC_ADDR_CTRL, RTC_CMD_WRITE_ENABLE);
 	if (status)
 		return status;
 
 	/* Write registers starting at the first time/date address. */
-	bp = buf;
-	*bp++ = RTC_CLCK_BURST << 1 | RTC_CMD_WRITE;
-
 	*bp++ = bin2bcd(time->tm_sec);
 	*bp++ = bin2bcd(time->tm_min);
 	*bp++ = bin2bcd(time->tm_hour);

@@ -69,23 +105,16 @@ static int ds1302_rtc_set_time(struct device *dev, struct rtc_time *time)
 	*bp++ = bin2bcd(time->tm_year % 100);
 	*bp++ = RTC_CMD_WRITE_DISABLE;
 
-	/* use write-then-read since dma from stack is nonportable */
-	return spi_write_then_read(spi, buf, sizeof(buf),
-			NULL, 0);
+	return ds1302_writeburst(ds1302, RTC_CLCK_BURST, buf, sizeof(buf));
 }
 
 static int ds1302_rtc_get_time(struct device *dev, struct rtc_time *time)
 {
-	struct spi_device	*spi = dev_get_drvdata(dev);
-	u8		addr = RTC_CLCK_BURST << 1 | RTC_CMD_READ;
+	struct ds1302	*ds1302 = dev_get_drvdata(dev);
 	u8		buf[RTC_CLCK_LEN - 1];
 	int		status;
 
-	/* Use write-then-read to get all the date/time registers
-	 * since dma from stack is nonportable
-	 */
-	status = spi_write_then_read(spi, &addr, sizeof(addr),
-			buf, sizeof(buf));
+	status = ds1302_readburst(ds1302, RTC_CLCK_BURST, buf, sizeof(buf));
 	if (status < 0)
 		return status;
 

@@ -107,94 +136,127 @@ static struct rtc_class_ops ds1302_rtc_ops = {
 	.set_time	= ds1302_rtc_set_time,
 };
 
-static int ds1302_probe(struct spi_device *spi)
+static int ds1302_probe(struct ds1302 *ds1302)
 {
 	struct rtc_device	*rtc;
-	u8		addr;
-	u8		buf[4];
-	u8		*bp = buf;
 	int		status;
 
-	/* 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)) {
-		dev_err(&spi->dev, "bad word length\n");
-		return -EINVAL;
-	} else if (spi->max_speed_hz > 2000000) {
-		dev_err(&spi->dev, "speed is too high\n");
-		return -EINVAL;
-	} else if (spi->mode & SPI_CPHA) {
-		dev_err(&spi->dev, "bad mode\n");
-		return -EINVAL;
-	}
+	dev_set_drvdata(ds1302->dev, ds1302);
 
-	addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
-	status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+	status = ds1302_readbyte(ds1302, RTC_ADDR_CTRL);
 	if (status < 0) {
-		dev_err(&spi->dev, "control register read error %d\n",
+		dev_err(ds1302->dev, "control register read error %d\n",
 				status);
 		return status;
 	}
 
-	if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
-		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+	if (status & ~RTC_CMD_WRITE_DISABLE) {
+		status = ds1302_readbyte(ds1302, RTC_ADDR_CTRL);
 		if (status < 0) {
-			dev_err(&spi->dev, "control register read error %d\n",
+			dev_err(ds1302->dev, "control register read error %d\n",
 					status);
 			return status;
 		}
 
-		if ((buf[0] & ~RTC_CMD_WRITE_DISABLE) != 0) {
-			dev_err(&spi->dev, "junk in control register\n");
+		if (status & ~RTC_CMD_WRITE_DISABLE) {
+			dev_err(ds1302->dev, "junk in control register\n");
 			return -ENODEV;
 		}
 	}
-	if (buf[0] == 0) {
-		bp = buf;
-		*bp++ = RTC_ADDR_CTRL << 1 | RTC_CMD_WRITE;
-		*bp++ = RTC_CMD_WRITE_DISABLE;
-
-		status = spi_write_then_read(spi, buf, 2, NULL, 0);
+	if (status == 0) {
+		status = ds1302_writebyte(ds1302, RTC_ADDR_CTRL,
+					  RTC_CMD_WRITE_DISABLE);
 		if (status < 0) {
-			dev_err(&spi->dev, "control register write error %d\n",
-					status);
+			dev_err(ds1302->dev,
+				"control register write error %d\n", status);
 			return status;
 		}
 
-		addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
-		status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+		status = ds1302_readbyte(ds1302, RTC_ADDR_CTRL);
 		if (status < 0) {
-			dev_err(&spi->dev,
+			dev_err(ds1302->dev,
 					"error %d reading control register\n",
 					status);
 			return status;
 		}
 
-		if (buf[0] != RTC_CMD_WRITE_DISABLE) {
-			dev_err(&spi->dev, "failed to detect chip\n");
+		if (status != RTC_CMD_WRITE_DISABLE) {
+			dev_err(ds1302->dev, "failed to detect chip\n");
 			return -ENODEV;
 		}
 	}
 
-	spi_set_drvdata(spi, spi);
-
-	rtc = devm_rtc_device_register(&spi->dev, "ds1302",
+	rtc = devm_rtc_device_register(ds1302->dev, "ds1302",
 			&ds1302_rtc_ops, THIS_MODULE);
 	if (IS_ERR(rtc)) {
 		status = PTR_ERR(rtc);
-		dev_err(&spi->dev, "error %d registering rtc\n", status);
+		dev_err(ds1302->dev, "error %d registering rtc\n", status);
 		return status;
 	}
 
 	return 0;
 }
 
-static int ds1302_remove(struct spi_device *spi)
+static int ds1302_spi_read(struct ds1302 *ds1302, u8 addr, u8 *buf, int size)
 {
-	spi_set_drvdata(spi, NULL);
-	return 0;
+	struct spi_device *spi = to_spi_device(ds1302->dev);
+
+	addr = addr << 1 | RTC_CMD_READ;
+
+	/* Use write-then-read to get all the date/time registers
+	 * since dma from stack is nonportable
+	 */
+	return spi_write_then_read(spi, &addr, sizeof(addr), buf, size);
+}
+
+static int ds1302_spi_write(struct ds1302 *ds1302, u8 addr, const u8 *buf,
+			    int size)
+{
+	struct spi_device *spi = to_spi_device(ds1302->dev);
+	u8 write_buf[RTC_CLCK_LEN + 1];
+
+	if (size + 1 > sizeof(write_buf))
+		return -EINVAL;
+
+	write_buf[0] = addr << 1 | RTC_CMD_WRITE;
+	memcpy(write_buf + 1, buf, size);
+
+	/* use write-then-read since dma from stack is nonportable */
+	return spi_write_then_read(spi, write_buf, size + 1, NULL, 0);
+}
+
+static const struct ds1302_ops ds1302_spi_ops = {
+	.read = ds1302_spi_read,
+	.write = ds1302_spi_write,
+};
+
+static int ds1302_spi_probe(struct spi_device *spi)
+{
+	struct ds1302		*ds1302;
+
+	/* 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)) {
+		dev_err(&spi->dev, "bad word length\n");
+		return -EINVAL;
+	} else if (spi->max_speed_hz > 2000000) {
+		dev_err(&spi->dev, "speed is too high\n");
+		return -EINVAL;
+	} else if (spi->mode & SPI_CPHA) {
+		dev_err(&spi->dev, "bad mode\n");
+		return -EINVAL;
+	}
+
+	ds1302 = devm_kzalloc(&spi->dev, sizeof(*ds1302), GFP_KERNEL);
+	if (!ds1302)
+		return -ENOMEM;
+
+	ds1302->ops = &ds1302_spi_ops;
+	ds1302->dev = &spi->dev;
+
+	return ds1302_probe(ds1302);
 }
 
 #ifdef CONFIG_OF

@@ -208,8 +270,7 @@ MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
 static struct spi_driver ds1302_driver = {
 	.driver.name	= "rtc-ds1302",
 	.driver.of_match_table = of_match_ptr(ds1302_dt_ids),
-	.probe		= ds1302_probe,
-	.remove		= ds1302_remove,
+	.probe		= ds1302_spi_probe,
 };
 
 module_spi_driver(ds1302_driver);