[PATCH 3/3] rtc: sd3078: new driver.

From: Dianlong Li
Date: Thu Dec 13 2018 - 05:14:22 EST

The sd3078 is a combination RTC and SRAM device with I2C interface.

Signed-off-by: Dianlong Li <long17.cool@xxxxxxx>
---
MAINTAINERS | 6 ++
drivers/rtc/Kconfig | 9 ++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-sd3078.c | 232 ++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 248 insertions(+)
create mode 100644 drivers/rtc/rtc-sd3078.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f485597..2ad8671 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16125,6 +16125,12 @@ L: linux-gpio@xxxxxxxxxxxxxxx
S: Maintained
F: drivers/gpio/gpio-wcove.c

+WHWAVE RTC DRIVER
+M: Dianlong Li <long17.cool@xxxxxxx>
+L: linux-rtc@xxxxxxxxxxxxxxx
+S: Maintained
+F: drivers/rtc/rtc-sd3078.c
+
WIIMOTE HID DRIVER
M: David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
L: linux-input@xxxxxxxxxxxxxxx
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index a819ef0..51a8255b 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -646,6 +646,15 @@ config RTC_DRV_S5M
This driver can also be built as a module. If so, the module
will be called rtc-s5m.

+config RTC_DRV_SD3078
+ tristate "ZXW Crystal SD3078"
+ help
+ If you say yes here you get support for the ZXW Crystal
+ SD3078 RTC chips.
+
+ This driver can also be built as a module. If so, the module
+ will be called rtc-sd3078
+
endif # I2C

comment "SPI RTC drivers"
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 290c173..91a9257 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -148,6 +148,7 @@ obj-$(CONFIG_RTC_DRV_S3C) += rtc-s3c.o
obj-$(CONFIG_RTC_DRV_S5M) += rtc-s5m.o
obj-$(CONFIG_RTC_DRV_SA1100) += rtc-sa1100.o
obj-$(CONFIG_RTC_DRV_SC27XX) += rtc-sc27xx.o
+obj-$(CONFIG_RTC_DRV_SD3078) += rtc-sd3078.o
obj-$(CONFIG_RTC_DRV_SH) += rtc-sh.o
obj-$(CONFIG_RTC_DRV_SIRFSOC) += rtc-sirfsoc.o
obj-$(CONFIG_RTC_DRV_SNVS) += rtc-snvs.o
diff --git a/drivers/rtc/rtc-sd3078.c b/drivers/rtc/rtc-sd3078.c
new file mode 100644
index 0000000..a70d7311
--- /dev/null
+++ b/drivers/rtc/rtc-sd3078.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Real Time Clock (RTC) Driver for sd3078
+ * Copyright (C) 2018 Zoro Li
+ */
+
+#include <linux/bcd.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+#define SD3078_REG_SC 0x00
+#define SD3078_REG_MN 0x01
+#define SD3078_REG_HR 0x02
+#define SD3078_REG_DW 0x03
+#define SD3078_REG_DM 0x04
+#define SD3078_REG_MO 0x05
+#define SD3078_REG_YR 0x06
+
+#define SD3078_REG_CTRL1 0x0f
+#define SD3078_REG_CTRL2 0x10
+#define SD3078_REG_CTRL3 0x11
+
+#define KEY_WRITE1 0x80
+#define KEY_WRITE2 0x04
+#define KEY_WRITE3 0x80
+
+#define NUM_TIME_REGS (SD3078_REG_YR - SD3078_REG_SC + 1)
+
+/*
+ * The sd3078 has write protection
+ * and we can choose whether or not to use it.
+ * Write protection is turned off by default.
+ */
+#define WRITE_PROTECT_EN 0
+
+struct sd3078 {
+ struct rtc_device *rtc;
+ struct regmap *regmap;
+};
+
+/*
+ * In order to prevent arbitrary modification of the time register,
+ * when modification of the register,
+ * the "write" bit needs to be written in a certain order.
+ * 1. set WRITE1 bit
+ * 2. set WRITE2 bit
+ * 3. set WRITE3 bit
+ */
+static void sd3078_enable_reg_write(struct sd3078 *sd3078)
+{
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,
+ KEY_WRITE1, KEY_WRITE1);
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
+ KEY_WRITE2, KEY_WRITE2);
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
+ KEY_WRITE3, KEY_WRITE3);
+}
+
+#if WRITE_PROTECT_EN
+/*
+ * In order to prevent arbitrary modification of the time register,
+ * we should disable the write function.
+ * when disable write,
+ * the "write" bit needs to be clear in a certain order.
+ * 1. clear WRITE2 bit
+ * 2. clear WRITE3 bit
+ * 3. clear WRITE1 bit
+ */
+static void sd3078_disable_reg_write(struct sd3078 *sd3078)
+{
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
+ KEY_WRITE2, 0);
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL1,
+ KEY_WRITE3, 0);
+ regmap_update_bits(sd3078->regmap, SD3078_REG_CTRL2,
+ KEY_WRITE1, 0);
+}
+#endif
+
+static int sd3078_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+ unsigned char hour;
+ unsigned char rtc_data[NUM_TIME_REGS] = {0};
+ struct i2c_client *client = to_i2c_client(dev);
+ struct sd3078 *sd3078 = i2c_get_clientdata(client);
+ int ret;
+
+ ret = regmap_bulk_read(sd3078->regmap, SD3078_REG_SC, rtc_data,
+ NUM_TIME_REGS);
+ if (ret < 0) {
+ dev_err(dev, "reading from RTC failed with err:%d\n", ret);
+ return ret;
+ }
+
+ tm->tm_sec = bcd2bin(rtc_data[SD3078_REG_SC] & 0x7F);
+ tm->tm_min = bcd2bin(rtc_data[SD3078_REG_MN] & 0x7F);
+
+ /*
+ * The sd3078 supports 12/24 hour mode.
+ * When getting time,
+ * we need to convert the 12 hour mode to the 24 hour mode.
+ */
+ hour = rtc_data[SD3078_REG_HR];
+ if (hour & 0x80) /* 24H MODE */
+ tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x3F);
+ else if (hour & 0x20) /* 12H MODE PM */
+ tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F) + 12;
+ else /* 12H MODE AM */
+ tm->tm_hour = bcd2bin(rtc_data[SD3078_REG_HR] & 0x1F);
+
+ tm->tm_mday = bcd2bin(rtc_data[SD3078_REG_DM] & 0x3F);
+ tm->tm_wday = rtc_data[SD3078_REG_DW] & 0x07;
+ tm->tm_mon = bcd2bin(rtc_data[SD3078_REG_MO] & 0x1F) - 1;
+ tm->tm_year = bcd2bin(rtc_data[SD3078_REG_YR]) + 100;
+
+ return 0;
+}
+
+static int sd3078_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+ unsigned char rtc_data[NUM_TIME_REGS];
+ struct i2c_client *client = to_i2c_client(dev);
+ struct sd3078 *sd3078 = i2c_get_clientdata(client);
+ int ret;
+
+ rtc_data[SD3078_REG_SC] = bin2bcd(tm->tm_sec);
+ rtc_data[SD3078_REG_MN] = bin2bcd(tm->tm_min);
+ rtc_data[SD3078_REG_HR] = bin2bcd(tm->tm_hour) | 0x80;
+ rtc_data[SD3078_REG_DM] = bin2bcd(tm->tm_mday);
+ rtc_data[SD3078_REG_DW] = tm->tm_wday & 0x07;
+ rtc_data[SD3078_REG_MO] = bin2bcd(tm->tm_mon) + 1;
+ rtc_data[SD3078_REG_YR] = bin2bcd(tm->tm_year - 100);
+
+#if WRITE_PROTECT_EN
+ sd3078_enable_reg_write(sd3078);
+#endif
+
+ ret = regmap_bulk_write(sd3078->regmap, SD3078_REG_SC, rtc_data,
+ NUM_TIME_REGS);
+ if (ret < 0) {
+ dev_err(dev, "writing to RTC failed with err:%d\n", ret);
+ return ret;
+ }
+
+#if WRITE_PROTECT_EN
+ sd3078_disable_reg_write(sd3078);
+#endif
+
+ return 0;
+}
+
+static const struct rtc_class_ops sd3078_rtc_ops = {
+ .read_time = sd3078_rtc_read_time,
+ .set_time = sd3078_rtc_set_time,
+};
+
+static const struct regmap_config regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = 0x11,
+};
+
+static int sd3078_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ int ret;
+ struct sd3078 *sd3078;
+
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -ENODEV;
+
+ sd3078 = devm_kzalloc(&client->dev, sizeof(*sd3078), GFP_KERNEL);
+ if (!sd3078)
+ return -ENOMEM;
+
+ sd3078->regmap = devm_regmap_init_i2c(client, &regmap_config);
+ if (IS_ERR(sd3078->regmap)) {
+ dev_err(&client->dev, "regmap allocation failed\n");
+ return PTR_ERR(sd3078->regmap);
+ }
+
+ i2c_set_clientdata(client, sd3078);
+
+ sd3078->rtc = devm_rtc_allocate_device(&client->dev);
+ if (IS_ERR(sd3078->rtc))
+ return PTR_ERR(sd3078->rtc);
+
+ sd3078->rtc->ops = &sd3078_rtc_ops;
+ sd3078->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+ sd3078->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+ ret = rtc_register_device(sd3078->rtc);
+ if (ret) {
+ dev_err(&client->dev, "failed to register rtc device\n");
+ return ret;
+ }
+
+ sd3078_enable_reg_write(sd3078);
+
+ return 0;
+}
+
+static const struct i2c_device_id sd3078_id[] = {
+ {"sd3078", 0},
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, sd3078_id);
+
+static const struct of_device_id rtc_dt_match[] = {
+ { .compatible = "whwave,sd3078" },
+ {},
+};
+MODULE_DEVICE_TABLE(of, rtc_dt_match);
+
+struct i2c_driver sd3078_driver = {
+ .driver = {
+ .name = "sd3078",
+ .owner = THIS_MODULE,
+ .of_match_table = of_match_ptr(rtc_dt_match),
+ },
+ .probe = sd3078_probe,
+ .id_table = sd3078_id,
+};
+
+module_i2c_driver(sd3078_driver);
+
+MODULE_AUTHOR("Dianlong Li <long17.cool@xxxxxxx>");
+MODULE_DESCRIPTION("SD3078 RTC driver");
+MODULE_LICENSE("GPL v2");
--
1.7.9.5