Hw rtc driver

11_rtc_driver/0001-11_RTC_DRIVER-Modify-am335x-boneblack.dts.patch

@@ -0,0 +1,32 @@
+From acf34999930dcbf3244d506fc131f8d6f8be72ae Mon Sep 17 00:00:00 2001
+From: Maryna Malakhova <maryna.malakhova@globallogic.com>
+Date: Wed, 14 Apr 2021 12:00:16 +0300
+Subject: [PATCH] 11_RTC_DRIVER: Modify am335x-boneblack.dts
+
+Change rtc record in the am335x-boneblack.dts
+Use "maxim,ds3231x" as compatible string
+
+Signed-off-by: Maryna Malakhova <maryna.malakhova@globallogic.com>
+---
+ arch/arm/boot/dts/am335x-boneblack.dts | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/arch/arm/boot/dts/am335x-boneblack.dts b/arch/arm/boot/dts/am335x-boneblack.dts
+index d154d3133c16..4e15a2aa862b 100644
+--- a/arch/arm/boot/dts/am335x-boneblack.dts
++++ b/arch/arm/boot/dts/am335x-boneblack.dts
+@@ -26,3 +26,11 @@
+		opp-supported-hw = <0x06 0x0100>;
+	};
+ };
++
++&i2c2 {
++	ds3231: ds3231@68 {
++		compatible = "maxim,ds3231x";
++		reg = <0x68>;
++	};
++};
++
+--
+2.25.1
+

11_rtc_driver/11_rtc_driver.c

@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-3.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+
+#define DS3231_REG_SECONDS      0x00
+#define DS3231_REG_MINUTES      0x01
+#define DS3231_REG_HOURS        0x02
+#define DS3231_REG_AMPM         0x02
+#define DS3231_REG_DAY          0x03
+#define DS3231_REG_DATE         0x04
+#define DS3231_REG_MONTH        0x05
+#define DS3231_REG_YEAR         0x06
+#define DS3231_REG_CR           0x0E       /* Control register */
+#define DS3231_REG_SR           0x0F       /* control/status register */
+/*Bit masks*/
+#define DS3231_REG_SR_OSF     0x80
+#define DS3231_REG_CR_nEOSC   0x80
+
+struct ds3231x {
+	struct device *dev;
+	struct regmap *regmap;
+	struct rtc_device *rtc;
+};
+
+static int ds3231x_check_rtc_status(struct device *dev)
+{
+	struct ds3231x *ds3231 = dev_get_drvdata(dev);
+	int ret = 0;
+	int control, stat;
+
+	ret = regmap_read(ds3231->regmap, DS3231_REG_SR, &stat);
+	if (ret)
+		return ret;
+
+	if (stat & DS3231_REG_SR_OSF)
+		pr_warn("oscillator discontinuity flagged, time unreliable\n");
+
+	stat &= ~DS3231_REG_SR_OSF;
+
+	ret = regmap_write(ds3231->regmap, DS3231_REG_SR, stat);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(ds3231->regmap, DS3231_REG_CR, &control);
+	if (ret)
+		return ret;
+
+	control &= ~DS3231_REG_CR_nEOSC;
+	return regmap_write(ds3231->regmap, DS3231_REG_CR, control);
+}
+
+static int ds3231x_read_time(struct device *dev, struct rtc_time *time)
+{
+	struct ds3231x *ds3231 = dev_get_drvdata(dev);
+	int ret;
+	u8 buf[7];
+	unsigned int year, month, day, hour, minute, second;
+	unsigned int week, twelve_hr, am_pm;
+	unsigned int century, add_century = 0;
+
+	ret = regmap_bulk_read(ds3231->regmap, DS3231_REG_SECONDS, buf, 7);
+	if (ret)
+		return ret;
+
+	second = buf[0];
+	minute = buf[1];
+	hour = buf[2];
+	week = buf[3];
+	day = buf[4];
+	month = buf[5];
+	year = buf[6];
+
+	/* Extract additional information for AM/PM and century */
+
+	twelve_hr = hour & 0x40;
+	am_pm = hour & 0x20;
+	century = month & 0x80;
+
+	/* Write to rtc_time structure */
+
+	time->tm_sec = bcd2bin(second);
+	time->tm_min = bcd2bin(minute);
+	if (twelve_hr) {
+		/* Convert to 24 hr */
+		if (am_pm)
+			time->tm_hour = bcd2bin(hour & 0x1F) + 12;
+		else
+			time->tm_hour = bcd2bin(hour & 0x1F);
+	} else {
+		time->tm_hour = bcd2bin(hour);
+	}
+
+	/* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
+	time->tm_wday = bcd2bin(week) - 1;
+	time->tm_mday = bcd2bin(day);
+	/* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
+	time->tm_mon = bcd2bin(month & 0x7F) - 1;
+	if (century)
+		add_century = 100;
+
+	time->tm_year = bcd2bin(year) + add_century;
+
+	return 0;
+}
+
+static int ds3231x_set_time(struct device *dev, struct rtc_time *time)
+{
+	struct ds3231x *ds3231 = dev_get_drvdata(dev);
+	u8 buf[7];
+
+	/* Extract time from rtc_time and load into ds3231*/
+	buf[0] = bin2bcd(time->tm_sec);
+	buf[1] = bin2bcd(time->tm_min);
+	buf[2] = bin2bcd(time->tm_hour);
+	/* Day of the week in linux range is 0~6 while 1~7 in RTC chip */
+	buf[3] = bin2bcd(time->tm_wday + 1);
+	buf[4] = bin2bcd(time->tm_mday); /* Date */
+	/* linux tm_mon range:0~11, while month range is 1~12 in RTC chip */
+	buf[5] = bin2bcd(time->tm_mon + 1);
+	if (time->tm_year >= 100) {
+		buf[5] |= 0x80;
+		buf[6] = bin2bcd(time->tm_year - 100);
+	} else {
+		buf[6] = bin2bcd(time->tm_year);
+	}
+
+	return regmap_bulk_write(ds3231->regmap, DS3231_REG_SECONDS, buf, 7);
+}
+
+static const struct rtc_class_ops ds3231x_rtc_ops = {
+	.read_time = ds3231x_read_time,
+	.set_time = ds3231x_set_time,
+};
+
+static int ds3231x_probe(struct device *dev, struct regmap *regmap, int irq,
+			const char *name)
+{
+	struct ds3231x *ds3231;
+	int ret;
+
+	ds3231 = devm_kzalloc(dev, sizeof(*ds3231), GFP_KERNEL);
+	if (!ds3231)
+		return -ENOMEM;
+
+	ds3231->regmap = regmap;
+	ds3231->dev = dev;
+	dev_set_drvdata(dev, ds3231);
+
+	ret = ds3231x_check_rtc_status(dev);
+	if (ret)
+		return ret;
+
+	ds3231->rtc = devm_rtc_device_register(dev, name, &ds3231x_rtc_ops,
+						THIS_MODULE);
+	if (IS_ERR(ds3231->rtc))
+		return PTR_ERR(ds3231->rtc);
+
+	return 0;
+}
+
+static int ds3231x_i2c_probe(struct i2c_client *client,
+			    const struct i2c_device_id *id)
+{
+	struct regmap *regmap;
+	static const struct regmap_config config = {
+		.reg_bits = 8,
+		.val_bits = 8,
+		.max_register = 0x12,
+	};
+
+	regmap = devm_regmap_init_i2c(client, &config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "%s: regmap allocation failed: %ld\n",
+			__func__, PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	return ds3231x_probe(&client->dev, regmap, client->irq, client->name);
+}
+
+
+static int ds3231x_remove(struct i2c_client *i2c)
+{
+	/*TODO*/
+	return 0;
+}
+
+
+static const struct i2c_device_id ds3231x_id[] = {
+	{"ds3231x"},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ds3231x_id);
+
+static const struct of_device_id ds3231x_of_match[] = {
+	{.compatible = "maxim, ds3231x"},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, ds3231x_of_match);
+
+static struct i2c_driver ds3231x_driver = {
+	.driver		= {
+		.name	= "ds3231x",
+		.of_match_table = ds3231x_of_match,
+	},
+	.probe	= ds3231x_i2c_probe,
+	.remove	= ds3231x_remove,
+	.id_table = ds3231x_id,
+};
+
+module_i2c_driver(ds3231x_driver);
+
+MODULE_AUTHOR("Malakhova.Maryna <maryna.malakhova@globallogic.com>");
+MODULE_DESCRIPTION("RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("0.1");

11_rtc_driver/11_rtc_log.txt

@@ -0,0 +1,45 @@
+Please press Enter to activate this console.
+/ #
+/ # dmesg | grep rtc
+[    2.213827] hctosys: unable to open rtc device (rtc0)
+/ #
+/ # hwclock
+hwclock: can't open '/dev/misc/rtc': No such file or directory
+/ #
+/ # find . | grep ds32
+./sys/firmware/devicetree/base/ocp/i2c@4819c000/ds3231@68
+./sys/firmware/devicetree/base/ocp/i2c@4819c000/ds3231@68/compatible
+./sys/firmware/devicetree/base/ocp/i2c@4819c000/ds3231@68/reg
+./sys/firmware/devicetree/base/ocp/i2c@4819c000/ds3231@68/name
+/ #
+/ # insmod /mnt/11_rtc_driver.ko
+[   73.495450] 11_rtc_driver: loading out-of-tree module taints kernel.
+[   73.506135] ds3231x 2-0068: rtc core: registered ds3231x as rtc0
+/ #
+/ # hwclock
+hwclock: RTC_RD_TIME: Invalid argument
+/ #
+/ # hwclock -w -f /dev/rtc0
+/ #
+/ # hwclock -r -f /dev/rtc0
+Thu Jan  1 00:02:22 1970  0.000000 seconds
+/ #
+/ #
+/ # date
+Thu Jan  1 00:08:02 UTC 1970
+/ # hwclock --show
+Thu Jan  1 00:08:34 1970  0.000000 seconds
+/ # date -s "2021-04-14 11:24:00"
+Wed Apr 14 11:24:00 UTC 2021
+/ # hwclock -w -f /dev/rtc0
+/ # hwclock -r -f /dev/rtc0
+Wed Apr 14 11:24:34 2021  0.000000 seconds
+/ # date -s "2014-04-14 11:24:00"
+Mon Apr 14 11:24:00 UTC 2014
+/ # date
+Mon Apr 14 11:24:02 UTC 2014
+/ # hwclock -s -f /dev/rtc0
+/ # date
+Wed Apr 14 11:25:11 UTC 2021
+/ #
+