v4.19.13 snapshot.
diff --git a/drivers/rtc/rtc-ds1302.c b/drivers/rtc/rtc-ds1302.c
new file mode 100644
index 0000000..2a88115
--- /dev/null
+++ b/drivers/rtc/rtc-ds1302.c
@@ -0,0 +1,218 @@
+/*
+ * Dallas DS1302 RTC Support
+ *
+ * Copyright (C) 2002 David McCullough
+ * Copyright (C) 2003 - 2007 Paul Mundt
+ *
+ * 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.
+ */
+
+#include <linux/bcd.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+
+#define DRV_NAME "rtc-ds1302"
+
+#define RTC_CMD_READ 0x81 /* Read command */
+#define RTC_CMD_WRITE 0x80 /* Write command */
+
+#define RTC_CMD_WRITE_ENABLE 0x00 /* Write enable */
+#define RTC_CMD_WRITE_DISABLE 0x80 /* Write disable */
+
+#define RTC_ADDR_RAM0 0x20 /* Address of RAM0 */
+#define RTC_ADDR_TCR 0x08 /* Address of trickle charge register */
+#define RTC_CLCK_BURST 0x1F /* Address of clock burst */
+#define RTC_CLCK_LEN 0x08 /* Size of clock burst */
+#define RTC_ADDR_CTRL 0x07 /* Address of control register */
+#define RTC_ADDR_YEAR 0x06 /* Address of year register */
+#define RTC_ADDR_DAY 0x05 /* Address of day of week register */
+#define RTC_ADDR_MON 0x04 /* Address of month register */
+#define RTC_ADDR_DATE 0x03 /* Address of day of month register */
+#define RTC_ADDR_HOUR 0x02 /* Address of hour register */
+#define RTC_ADDR_MIN 0x01 /* Address of minute register */
+#define RTC_ADDR_SEC 0x00 /* Address of second register */
+
+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];
+ u8 *bp;
+ 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);
+ 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);
+ *bp++ = bin2bcd(time->tm_mday);
+ *bp++ = bin2bcd(time->tm_mon + 1);
+ *bp++ = time->tm_wday + 1;
+ *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);
+}
+
+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;
+ 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));
+ if (status < 0)
+ return status;
+
+ /* Decode the registers */
+ time->tm_sec = bcd2bin(buf[RTC_ADDR_SEC]);
+ time->tm_min = bcd2bin(buf[RTC_ADDR_MIN]);
+ time->tm_hour = bcd2bin(buf[RTC_ADDR_HOUR]);
+ time->tm_wday = buf[RTC_ADDR_DAY] - 1;
+ time->tm_mday = bcd2bin(buf[RTC_ADDR_DATE]);
+ time->tm_mon = bcd2bin(buf[RTC_ADDR_MON]) - 1;
+ time->tm_year = bcd2bin(buf[RTC_ADDR_YEAR]) + 100;
+
+ return 0;
+}
+
+static const struct rtc_class_ops ds1302_rtc_ops = {
+ .read_time = ds1302_rtc_get_time,
+ .set_time = ds1302_rtc_set_time,
+};
+
+static int ds1302_probe(struct spi_device *spi)
+{
+ struct rtc_device *rtc;
+ u8 addr;
+ u8 buf[4];
+ u8 *bp;
+ 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;
+ }
+
+ addr = RTC_ADDR_CTRL << 1 | RTC_CMD_READ;
+ status = spi_write_then_read(spi, &addr, sizeof(addr), buf, 1);
+ if (status < 0) {
+ dev_err(&spi->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 < 0) {
+ dev_err(&spi->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");
+ 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) {
+ dev_err(&spi->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);
+ if (status < 0) {
+ dev_err(&spi->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");
+ return -ENODEV;
+ }
+ }
+
+ spi_set_drvdata(spi, spi);
+
+ rtc = devm_rtc_device_register(&spi->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);
+ return status;
+ }
+
+ return 0;
+}
+
+static int ds1302_remove(struct spi_device *spi)
+{
+ spi_set_drvdata(spi, NULL);
+ return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ds1302_dt_ids[] = {
+ { .compatible = "maxim,ds1302", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ds1302_dt_ids);
+#endif
+
+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,
+};
+
+module_spi_driver(ds1302_driver);
+
+MODULE_DESCRIPTION("Dallas DS1302 RTC driver");
+MODULE_AUTHOR("Paul Mundt, David McCullough");
+MODULE_LICENSE("GPL v2");