--- /dev/null
+/*
+ * SII Semiconductor Corporation S35392A RTC driver.
+ *
+ * Copyright (c) 2017, General Electric Company
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#include <command.h>
+#include <common.h>
+#include <dm.h>
+#include <i2c.h>
+#include <linux/bitrev.h>
+#include <rtc.h>
+
+#define S35390A_CMD_STATUS1 0x30
+#define S35390A_CMD_STATUS2 0x31
+#define S35390A_CMD_TIME1 0x32
+#define S35390A_CMD_TIME2 0x33
+#define S35390A_CMD_INT2_REG1 0x35
+
+#define S35390A_BYTE_YEAR 0
+#define S35390A_BYTE_MONTH 1
+#define S35390A_BYTE_DAY 2
+#define S35390A_BYTE_WDAY 3
+#define S35390A_BYTE_HOURS 4
+#define S35390A_BYTE_MINS 5
+#define S35390A_BYTE_SECS 6
+
+/* flags for STATUS1 */
+#define S35390A_FLAG_POC 0x01
+#define S35390A_FLAG_BLD 0x02
+#define S35390A_FLAG_INT2 0x04
+#define S35390A_FLAG_24H 0x40
+#define S35390A_FLAG_RESET 0x80
+
+/*
+ * If either BLD or POC is set, then the chip has lost power long enough for
+ * the time value to become invalid.
+ */
+#define S35390A_LOW_VOLTAGE (S35390A_FLAG_POC | S35390A_FLAG_BLD)
+
+/*---------------------------------------------------------------------*/
+#undef DEBUG_RTC
+
+#ifdef DEBUG_RTC
+#define DEBUGR(fmt, args...) printf(fmt, ##args)
+#else
+#define DEBUGR(fmt, args...)
+#endif
+/*---------------------------------------------------------------------*/
+
+#ifdef CONFIG_DM_RTC
+#define DEV_TYPE struct udevice
+#else
+/* Local udevice */
+struct ludevice {
+ u8 chip;
+};
+
+#define DEV_TYPE struct ludevice
+struct ludevice dev;
+
+#endif
+
+#define msleep(a) udelay(a * 1000)
+
+int lowvoltage;
+
+static int s35392a_rtc_reset(DEV_TYPE *dev);
+
+static int s35392a_rtc_read(DEV_TYPE *dev, u8 reg, u8 *buf, int len)
+{
+ int ret;
+
+#ifdef CONFIG_DM_RTC
+ /* TODO: we need to tweak the chip address to reg */
+ ret = dm_i2c_read(dev, 0, buf, len);
+#else
+ (void)dev;
+ ret = i2c_read(reg, 0, -1, buf, len);
+#endif
+
+ return ret;
+}
+
+static int s35392a_rtc_write(DEV_TYPE *dev, u8 reg, u8 *buf, int len)
+{
+ int ret;
+
+#ifdef CONFIG_DM_RTC
+ /* TODO: we need to tweak the chip address to reg */
+ ret = dm_i2c_write(dev, 0, buf, 1);
+#else
+ (void)dev;
+ ret = i2c_write(reg, 0, 0, buf, len);
+#endif
+
+ return ret;
+}
+
+static int s35392a_rtc_read8(DEV_TYPE *dev, unsigned int reg)
+{
+ u8 val;
+ int ret;
+
+ ret = s35392a_rtc_read(dev, reg, &val, sizeof(val));
+ return ret < 0 ? ret : val;
+}
+
+static int s35392a_rtc_write8(DEV_TYPE *dev, unsigned int reg, int val)
+{
+ int ret;
+ u8 lval = val;
+
+ ret = s35392a_rtc_write(dev, reg, &lval, sizeof(lval));
+ return ret < 0 ? ret : 0;
+}
+
+static int validate_time(const struct rtc_time *tm)
+{
+ if ((tm->tm_year < 2000) || (tm->tm_year > 2099))
+ return -EINVAL;
+
+ if ((tm->tm_mon < 1) || (tm->tm_mon > 12))
+ return -EINVAL;
+
+ if ((tm->tm_mday < 1) || (tm->tm_mday > 31))
+ return -EINVAL;
+
+ if ((tm->tm_wday < 0) || (tm->tm_wday > 6))
+ return -EINVAL;
+
+ if ((tm->tm_hour < 0) || (tm->tm_hour > 23))
+ return -EINVAL;
+
+ if ((tm->tm_min < 0) || (tm->tm_min > 59))
+ return -EINVAL;
+
+ if ((tm->tm_sec < 0) || (tm->tm_sec > 59))
+ return -EINVAL;
+
+ return 0;
+}
+
+void s35392a_rtc_init(DEV_TYPE *dev)
+{
+ int status;
+
+ status = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
+ if (status < 0)
+ goto error;
+
+ DEBUGR("init: S35390A_CMD_STATUS1: 0x%x\n", status);
+
+ lowvoltage = status & S35390A_LOW_VOLTAGE ? 1 : 0;
+
+ if (status & S35390A_FLAG_POC)
+ /*
+ * Do not communicate for 0.5 seconds since the power-on
+ * detection circuit is in operation.
+ */
+ msleep(500);
+
+ else if (!lowvoltage)
+ /*
+ * If both POC and BLD are unset everything is fine.
+ */
+ return;
+
+ if (lowvoltage)
+ printf("RTC low voltage detected\n");
+
+ if (!s35392a_rtc_reset(dev))
+ return;
+
+error:
+ printf("Error RTC init.\n");
+}
+
+/* Get the current time from the RTC */
+static int s35392a_rtc_get(DEV_TYPE *dev, struct rtc_time *tm)
+{
+ u8 date[7];
+ int ret, i;
+
+ if (lowvoltage) {
+ DEBUGR("RTC low voltage detected\n");
+ return -EINVAL;
+ }
+
+ ret = s35392a_rtc_read(dev, S35390A_CMD_TIME1, date, sizeof(date));
+ if (ret < 0) {
+ DEBUGR("Error reading date from RTC\n");
+ return -EIO;
+ }
+
+ /* This chip returns the bits of each byte in reverse order */
+ for (i = 0; i < 7; ++i)
+ date[i] = bitrev8(date[i]);
+
+ tm->tm_sec = bcd2bin(date[S35390A_BYTE_SECS]);
+ tm->tm_min = bcd2bin(date[S35390A_BYTE_MINS]);
+ tm->tm_hour = bcd2bin(date[S35390A_BYTE_HOURS] & ~S35390A_FLAG_24H);
+ tm->tm_wday = bcd2bin(date[S35390A_BYTE_WDAY]);
+ tm->tm_mday = bcd2bin(date[S35390A_BYTE_DAY]);
+ tm->tm_mon = bcd2bin(date[S35390A_BYTE_MONTH]);
+ tm->tm_year = bcd2bin(date[S35390A_BYTE_YEAR]) + 2000;
+
+ DEBUGR("Get DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
+ tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
+ tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+ return 0;
+}
+
+/* Set the RTC */
+static int s35392a_rtc_set(DEV_TYPE *dev, const struct rtc_time *tm)
+{
+ int i, ret;
+ int status;
+ u8 date[7];
+
+ DEBUGR("Set DATE: %4d-%02d-%02d (wday=%d) TIME: %2d:%02d:%02d\n",
+ tm->tm_year, tm->tm_mon, tm->tm_mday, tm->tm_wday,
+ tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+ ret = validate_time(tm);
+ if (ret < 0)
+ return -EINVAL;
+
+ /* We support only 24h mode */
+ ret = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
+ if (ret < 0)
+ return -EIO;
+ status = ret;
+
+ ret = s35392a_rtc_write8(dev, S35390A_CMD_STATUS1,
+ status | S35390A_FLAG_24H);
+ if (ret < 0)
+ return -EIO;
+
+ date[S35390A_BYTE_YEAR] = bin2bcd(tm->tm_year - 2000);
+ date[S35390A_BYTE_MONTH] = bin2bcd(tm->tm_mon);
+ date[S35390A_BYTE_DAY] = bin2bcd(tm->tm_mday);
+ date[S35390A_BYTE_WDAY] = bin2bcd(tm->tm_wday);
+ date[S35390A_BYTE_HOURS] = bin2bcd(tm->tm_hour);
+ date[S35390A_BYTE_MINS] = bin2bcd(tm->tm_min);
+ date[S35390A_BYTE_SECS] = bin2bcd(tm->tm_sec);
+
+ /* This chip expects the bits of each byte to be in reverse order */
+ for (i = 0; i < 7; ++i)
+ date[i] = bitrev8(date[i]);
+
+ ret = s35392a_rtc_write(dev, S35390A_CMD_TIME1, date, sizeof(date));
+ if (ret < 0) {
+ DEBUGR("Error writing date to RTC\n");
+ return -EIO;
+ }
+
+ /* Now we have time. Reset the low voltage status */
+ lowvoltage = 0;
+
+ return 0;
+}
+
+/* Reset the RTC. */
+static int s35392a_rtc_reset(DEV_TYPE *dev)
+{
+ int buf;
+ int ret;
+ unsigned int initcount = 0;
+
+ buf = S35390A_FLAG_RESET;
+
+initialize:
+ ret = s35392a_rtc_write8(dev, S35390A_CMD_STATUS1, buf);
+ if (ret < 0)
+ return -EIO;
+
+ ret = s35392a_rtc_read8(dev, S35390A_CMD_STATUS1);
+ if (ret < 0)
+ return -EIO;
+ buf = ret;
+
+ if (!lowvoltage)
+ lowvoltage = buf & S35390A_LOW_VOLTAGE ? 1 : 0;
+
+ if (buf & S35390A_LOW_VOLTAGE) {
+ /* Try up to five times to reset the chip */
+ if (initcount < 5) {
+ ++initcount;
+ goto initialize;
+ } else {
+ return -EIO;
+ }
+ }
+
+ return 0;
+}
+
+#ifndef CONFIG_DM_RTC
+
+int rtc_get(struct rtc_time *tm)
+{
+ return s35392a_rtc_get(&dev, tm);
+}
+
+int rtc_set(struct rtc_time *tm)
+{
+ return s35392a_rtc_set(&dev, tm);
+}
+
+void rtc_reset(void)
+{
+ s35392a_rtc_reset(&dev);
+}
+
+void rtc_init(void)
+{
+ s35392a_rtc_init(&dev);
+}
+
+#else
+
+static int s35392a_probe(struct udevice *dev)
+{
+ s35392a_rtc_init(dev);
+ return 0;
+}
+
+static const struct rtc_ops s35392a_rtc_ops = {
+ .get = s35392a_rtc_get,
+ .set = s35392a_rtc_set,
+ .read8 = s35392a_rtc_read8,
+ .write8 = s35392a_rtc_write8,
+ .reset = s35392a_rtc_reset,
+};
+
+static const struct udevice_id s35392a_rtc_ids[] = {
+ { .compatible = "sii,s35392a-rtc" },
+ { }
+};
+
+U_BOOT_DRIVER(s35392a_rtc) = {
+ .name = "s35392a_rtc",
+ .id = UCLASS_RTC,
+ .probe = s35392a_probe,
+ .of_match = s35392a_rtc_ids,
+ .ops = &s35392a_rtc_ops,
+};
+
+#endif
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