v4.19.13 snapshot.
diff --git a/drivers/rtc/rtc-m48t86.c b/drivers/rtc/rtc-m48t86.c
new file mode 100644
index 0000000..a953353
--- /dev/null
+++ b/drivers/rtc/rtc-m48t86.c
@@ -0,0 +1,295 @@
+/*
+ * ST M48T86 / Dallas DS12887 RTC driver
+ * Copyright (c) 2006 Tower Technologies
+ *
+ * Author: Alessandro Zummo <a.zummo@towertech.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This drivers only supports the clock running in BCD and 24H mode.
+ * If it will be ever adapted to binary and 12H mode, care must be taken
+ * to not introduce bugs.
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+#include <linux/bcd.h>
+#include <linux/io.h>
+
+#define M48T86_SEC 0x00
+#define M48T86_SECALRM 0x01
+#define M48T86_MIN 0x02
+#define M48T86_MINALRM 0x03
+#define M48T86_HOUR 0x04
+#define M48T86_HOURALRM 0x05
+#define M48T86_DOW 0x06 /* 1 = sunday */
+#define M48T86_DOM 0x07
+#define M48T86_MONTH 0x08 /* 1 - 12 */
+#define M48T86_YEAR 0x09 /* 0 - 99 */
+#define M48T86_A 0x0a
+#define M48T86_B 0x0b
+#define M48T86_B_SET BIT(7)
+#define M48T86_B_DM BIT(2)
+#define M48T86_B_H24 BIT(1)
+#define M48T86_C 0x0c
+#define M48T86_D 0x0d
+#define M48T86_D_VRT BIT(7)
+#define M48T86_NVRAM(x) (0x0e + (x))
+#define M48T86_NVRAM_LEN 114
+
+struct m48t86_rtc_info {
+ void __iomem *index_reg;
+ void __iomem *data_reg;
+ struct rtc_device *rtc;
+};
+
+static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
+{
+ struct m48t86_rtc_info *info = dev_get_drvdata(dev);
+ unsigned char value;
+
+ writeb(addr, info->index_reg);
+ value = readb(info->data_reg);
+
+ return value;
+}
+
+static void m48t86_writeb(struct device *dev,
+ unsigned char value, unsigned long addr)
+{
+ struct m48t86_rtc_info *info = dev_get_drvdata(dev);
+
+ writeb(addr, info->index_reg);
+ writeb(value, info->data_reg);
+}
+
+static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+ unsigned char reg;
+
+ reg = m48t86_readb(dev, M48T86_B);
+
+ if (reg & M48T86_B_DM) {
+ /* data (binary) mode */
+ tm->tm_sec = m48t86_readb(dev, M48T86_SEC);
+ tm->tm_min = m48t86_readb(dev, M48T86_MIN);
+ tm->tm_hour = m48t86_readb(dev, M48T86_HOUR) & 0x3f;
+ tm->tm_mday = m48t86_readb(dev, M48T86_DOM);
+ /* tm_mon is 0-11 */
+ tm->tm_mon = m48t86_readb(dev, M48T86_MONTH) - 1;
+ tm->tm_year = m48t86_readb(dev, M48T86_YEAR) + 100;
+ tm->tm_wday = m48t86_readb(dev, M48T86_DOW);
+ } else {
+ /* bcd mode */
+ tm->tm_sec = bcd2bin(m48t86_readb(dev, M48T86_SEC));
+ tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN));
+ tm->tm_hour = bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
+ 0x3f);
+ tm->tm_mday = bcd2bin(m48t86_readb(dev, M48T86_DOM));
+ /* tm_mon is 0-11 */
+ tm->tm_mon = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
+ tm->tm_year = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
+ tm->tm_wday = bcd2bin(m48t86_readb(dev, M48T86_DOW));
+ }
+
+ /* correct the hour if the clock is in 12h mode */
+ if (!(reg & M48T86_B_H24))
+ if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
+ tm->tm_hour += 12;
+
+ return 0;
+}
+
+static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+ unsigned char reg;
+
+ reg = m48t86_readb(dev, M48T86_B);
+
+ /* update flag and 24h mode */
+ reg |= M48T86_B_SET | M48T86_B_H24;
+ m48t86_writeb(dev, reg, M48T86_B);
+
+ if (reg & M48T86_B_DM) {
+ /* data (binary) mode */
+ m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
+ m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
+ m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
+ m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
+ m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
+ m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
+ m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
+ } else {
+ /* bcd mode */
+ m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
+ m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
+ m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
+ m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
+ m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
+ m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
+ m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
+ }
+
+ /* update ended */
+ reg &= ~M48T86_B_SET;
+ m48t86_writeb(dev, reg, M48T86_B);
+
+ return 0;
+}
+
+static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+ unsigned char reg;
+
+ reg = m48t86_readb(dev, M48T86_B);
+
+ seq_printf(seq, "mode\t\t: %s\n",
+ (reg & M48T86_B_DM) ? "binary" : "bcd");
+
+ reg = m48t86_readb(dev, M48T86_D);
+
+ seq_printf(seq, "battery\t\t: %s\n",
+ (reg & M48T86_D_VRT) ? "ok" : "exhausted");
+
+ return 0;
+}
+
+static const struct rtc_class_ops m48t86_rtc_ops = {
+ .read_time = m48t86_rtc_read_time,
+ .set_time = m48t86_rtc_set_time,
+ .proc = m48t86_rtc_proc,
+};
+
+static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
+ size_t count)
+{
+ struct device *dev = priv;
+ unsigned int i;
+
+ for (i = 0; i < count; i++)
+ ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
+
+ return 0;
+}
+
+static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
+ size_t count)
+{
+ struct device *dev = priv;
+ unsigned int i;
+
+ for (i = 0; i < count; i++)
+ m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
+
+ return 0;
+}
+
+/*
+ * The RTC is an optional feature at purchase time on some Technologic Systems
+ * boards. Verify that it actually exists by checking if the last two bytes
+ * of the NVRAM can be changed.
+ *
+ * This is based on the method used in their rtc7800.c example.
+ */
+static bool m48t86_verify_chip(struct platform_device *pdev)
+{
+ unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
+ unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
+ unsigned char tmp0, tmp1;
+
+ tmp0 = m48t86_readb(&pdev->dev, offset0);
+ tmp1 = m48t86_readb(&pdev->dev, offset1);
+
+ m48t86_writeb(&pdev->dev, 0x00, offset0);
+ m48t86_writeb(&pdev->dev, 0x55, offset1);
+ if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
+ m48t86_writeb(&pdev->dev, 0xaa, offset1);
+ if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
+ m48t86_readb(&pdev->dev, offset0) == 0x00) {
+ m48t86_writeb(&pdev->dev, tmp0, offset0);
+ m48t86_writeb(&pdev->dev, tmp1, offset1);
+
+ return true;
+ }
+ }
+ return false;
+}
+
+static int m48t86_rtc_probe(struct platform_device *pdev)
+{
+ struct m48t86_rtc_info *info;
+ struct resource *res;
+ unsigned char reg;
+ int err;
+ struct nvmem_config m48t86_nvmem_cfg = {
+ .name = "m48t86_nvram",
+ .word_size = 1,
+ .stride = 1,
+ .size = M48T86_NVRAM_LEN,
+ .reg_read = m48t86_nvram_read,
+ .reg_write = m48t86_nvram_write,
+ .priv = &pdev->dev,
+ };
+
+ info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res)
+ return -ENODEV;
+ info->index_reg = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(info->index_reg))
+ return PTR_ERR(info->index_reg);
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+ if (!res)
+ return -ENODEV;
+ info->data_reg = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(info->data_reg))
+ return PTR_ERR(info->data_reg);
+
+ dev_set_drvdata(&pdev->dev, info);
+
+ if (!m48t86_verify_chip(pdev)) {
+ dev_info(&pdev->dev, "RTC not present\n");
+ return -ENODEV;
+ }
+
+ info->rtc = devm_rtc_allocate_device(&pdev->dev);
+ if (IS_ERR(info->rtc))
+ return PTR_ERR(info->rtc);
+
+ info->rtc->ops = &m48t86_rtc_ops;
+ info->rtc->nvram_old_abi = true;
+
+ err = rtc_register_device(info->rtc);
+ if (err)
+ return err;
+
+ rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
+
+ /* read battery status */
+ reg = m48t86_readb(&pdev->dev, M48T86_D);
+ dev_info(&pdev->dev, "battery %s\n",
+ (reg & M48T86_D_VRT) ? "ok" : "exhausted");
+
+ return 0;
+}
+
+static struct platform_driver m48t86_rtc_platform_driver = {
+ .driver = {
+ .name = "rtc-m48t86",
+ },
+ .probe = m48t86_rtc_probe,
+};
+
+module_platform_driver(m48t86_rtc_platform_driver);
+
+MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
+MODULE_DESCRIPTION("M48T86 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rtc-m48t86");