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path: root/drivers/rtc/rtc-m48t35.c
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-rw-r--r--drivers/rtc/rtc-m48t35.c193
1 files changed, 193 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-m48t35.c b/drivers/rtc/rtc-m48t35.c
new file mode 100644
index 000000000..92f19bf99
--- /dev/null
+++ b/drivers/rtc/rtc-m48t35.c
@@ -0,0 +1,193 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
+ *
+ * Copyright (C) 2000 Silicon Graphics, Inc.
+ * Written by Ulf Carlsson (ulfc@engr.sgi.com)
+ *
+ * Copyright (C) 2008 Thomas Bogendoerfer
+ *
+ * Based on code written by Paul Gortmaker.
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/bcd.h>
+#include <linux/io.h>
+#include <linux/err.h>
+
+struct m48t35_rtc {
+ u8 pad[0x7ff8]; /* starts at 0x7ff8 */
+#ifdef CONFIG_SGI_IP27
+ u8 hour;
+ u8 min;
+ u8 sec;
+ u8 control;
+ u8 year;
+ u8 month;
+ u8 date;
+ u8 day;
+#else
+ u8 control;
+ u8 sec;
+ u8 min;
+ u8 hour;
+ u8 day;
+ u8 date;
+ u8 month;
+ u8 year;
+#endif
+};
+
+#define M48T35_RTC_SET 0x80
+#define M48T35_RTC_READ 0x40
+
+struct m48t35_priv {
+ struct rtc_device *rtc;
+ struct m48t35_rtc __iomem *reg;
+ size_t size;
+ unsigned long baseaddr;
+ spinlock_t lock;
+};
+
+static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
+{
+ struct m48t35_priv *priv = dev_get_drvdata(dev);
+ u8 control;
+
+ /*
+ * Only the values that we read from the RTC are set. We leave
+ * tm_wday, tm_yday and tm_isdst untouched. Even though the
+ * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
+ * by the RTC when initially set to a non-zero value.
+ */
+ spin_lock_irq(&priv->lock);
+ control = readb(&priv->reg->control);
+ writeb(control | M48T35_RTC_READ, &priv->reg->control);
+ tm->tm_sec = readb(&priv->reg->sec);
+ tm->tm_min = readb(&priv->reg->min);
+ tm->tm_hour = readb(&priv->reg->hour);
+ tm->tm_mday = readb(&priv->reg->date);
+ tm->tm_mon = readb(&priv->reg->month);
+ tm->tm_year = readb(&priv->reg->year);
+ writeb(control, &priv->reg->control);
+ spin_unlock_irq(&priv->lock);
+
+ tm->tm_sec = bcd2bin(tm->tm_sec);
+ tm->tm_min = bcd2bin(tm->tm_min);
+ tm->tm_hour = bcd2bin(tm->tm_hour);
+ tm->tm_mday = bcd2bin(tm->tm_mday);
+ tm->tm_mon = bcd2bin(tm->tm_mon);
+ tm->tm_year = bcd2bin(tm->tm_year);
+
+ /*
+ * Account for differences between how the RTC uses the values
+ * and how they are defined in a struct rtc_time;
+ */
+ tm->tm_year += 70;
+ if (tm->tm_year <= 69)
+ tm->tm_year += 100;
+
+ tm->tm_mon--;
+ return 0;
+}
+
+static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
+{
+ struct m48t35_priv *priv = dev_get_drvdata(dev);
+ unsigned char mon, day, hrs, min, sec;
+ unsigned int yrs;
+ u8 control;
+
+ yrs = tm->tm_year + 1900;
+ mon = tm->tm_mon + 1; /* tm_mon starts at zero */
+ day = tm->tm_mday;
+ hrs = tm->tm_hour;
+ min = tm->tm_min;
+ sec = tm->tm_sec;
+
+ if (yrs < 1970)
+ return -EINVAL;
+
+ yrs -= 1970;
+ if (yrs > 255) /* They are unsigned */
+ return -EINVAL;
+
+ if (yrs > 169)
+ return -EINVAL;
+
+ if (yrs >= 100)
+ yrs -= 100;
+
+ sec = bin2bcd(sec);
+ min = bin2bcd(min);
+ hrs = bin2bcd(hrs);
+ day = bin2bcd(day);
+ mon = bin2bcd(mon);
+ yrs = bin2bcd(yrs);
+
+ spin_lock_irq(&priv->lock);
+ control = readb(&priv->reg->control);
+ writeb(control | M48T35_RTC_SET, &priv->reg->control);
+ writeb(yrs, &priv->reg->year);
+ writeb(mon, &priv->reg->month);
+ writeb(day, &priv->reg->date);
+ writeb(hrs, &priv->reg->hour);
+ writeb(min, &priv->reg->min);
+ writeb(sec, &priv->reg->sec);
+ writeb(control, &priv->reg->control);
+ spin_unlock_irq(&priv->lock);
+ return 0;
+}
+
+static const struct rtc_class_ops m48t35_ops = {
+ .read_time = m48t35_read_time,
+ .set_time = m48t35_set_time,
+};
+
+static int m48t35_probe(struct platform_device *pdev)
+{
+ struct resource *res;
+ struct m48t35_priv *priv;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res)
+ return -ENODEV;
+ priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->size = resource_size(res);
+ if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
+ pdev->name))
+ return -EBUSY;
+
+ priv->baseaddr = res->start;
+ priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
+ if (!priv->reg)
+ return -ENOMEM;
+
+ spin_lock_init(&priv->lock);
+
+ platform_set_drvdata(pdev, priv);
+
+ priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
+ &m48t35_ops, THIS_MODULE);
+ return PTR_ERR_OR_ZERO(priv->rtc);
+}
+
+static struct platform_driver m48t35_platform_driver = {
+ .driver = {
+ .name = "rtc-m48t35",
+ },
+ .probe = m48t35_probe,
+};
+
+module_platform_driver(m48t35_platform_driver);
+
+MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
+MODULE_DESCRIPTION("M48T35 RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rtc-m48t35");