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Subject[PATCH v2] rtc: ds1307: add support for watchdog timer on ds1388
Date
The DS1388 variant has watchdog timer capabilities. When using a DS1388
and having enabled CONFIG_WATCHDOG_CORE register a watchdog device for
the DS1388.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---
This is going to the linux-watchdog list as well this time so it's probably the
first time the watchdog maintainers have seen it.

Changes in v2:
- Address review comments from Alexandre, the only functional change is setting
the hundredths of seconds to 0 instead of 99.

drivers/rtc/rtc-ds1307.c | 97 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 97 insertions(+)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 31a38d468378..1452982c3a6a 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -22,6 +22,7 @@
#include <linux/hwmon-sysfs.h>
#include <linux/clk-provider.h>
#include <linux/regmap.h>
+#include <linux/watchdog.h>

/*
* We can't determine type by probing, but if we expect pre-Linux code
@@ -144,8 +145,15 @@ enum ds_type {
# define M41TXX_BIT_CALIB_SIGN BIT(5)
# define M41TXX_M_CALIBRATION GENMASK(4, 0)

+#define DS1388_REG_WDOG_HUN_SECS 0x08
+#define DS1388_REG_WDOG_SECS 0x09
#define DS1388_REG_FLAG 0x0b
+# define DS1388_BIT_WF BIT(6)
# define DS1388_BIT_OSF BIT(7)
+#define DS1388_REG_CONTROL 0x0c
+# define DS1388_BIT_RST BIT(0)
+# define DS1388_BIT_WDE BIT(1)
+
/* negative offset step is -2.034ppm */
#define M41TXX_NEG_OFFSET_STEP_PPB 2034
/* positive offset step is +4.068ppm */
@@ -166,6 +174,9 @@ struct ds1307 {
#ifdef CONFIG_COMMON_CLK
struct clk_hw clks[2];
#endif
+#ifdef CONFIG_WATCHDOG_CORE
+ struct watchdog_device wdt;
+#endif
};

struct chip_desc {
@@ -854,6 +865,58 @@ static int m41txx_rtc_set_offset(struct device *dev, long offset)
ctrl_reg);
}

+#ifdef CONFIG_WATCHDOG_CORE
+static int ds1388_wdt_start(struct watchdog_device *wdt_dev)
+{
+ struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
+ u8 regs[2];
+ int ret;
+
+ ret = regmap_update_bits(ds1307->regmap, DS1388_REG_FLAG,
+ DS1388_BIT_WF, 0);
+ if (ret)
+ return ret;
+
+ ret = regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
+ DS1388_BIT_WDE | DS1388_BIT_RST, 0);
+ if (ret)
+ return ret;
+
+ /*
+ * watchdog timeouts are measured in seconds. So ignore hundreths of
+ * seconds field.
+ */
+ regs[0] = 0;
+ regs[1] = bin2bcd(wdt_dev->timeout);
+
+ ret = regmap_bulk_write(ds1307->regmap, DS1388_REG_WDOG_HUN_SECS, regs,
+ sizeof(regs));
+ if (ret)
+ return ret;
+
+ return regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
+ DS1388_BIT_WDE | DS1388_BIT_RST,
+ DS1388_BIT_WDE | DS1388_BIT_RST);
+}
+
+static int ds1388_wdt_stop(struct watchdog_device *wdt_dev)
+{
+ struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
+
+ return regmap_update_bits(ds1307->regmap, DS1388_REG_CONTROL,
+ DS1388_BIT_WDE | DS1388_BIT_RST, 0);
+}
+
+static int ds1388_wdt_ping(struct watchdog_device *wdt_dev)
+{
+ struct ds1307 *ds1307 = watchdog_get_drvdata(wdt_dev);
+ u8 regs[2];
+
+ return regmap_bulk_read(ds1307->regmap, DS1388_REG_WDOG_HUN_SECS, regs,
+ sizeof(regs));
+}
+#endif
+
static const struct rtc_class_ops rx8130_rtc_ops = {
.read_time = ds1307_get_time,
.set_time = ds1307_set_time,
@@ -1576,6 +1639,39 @@ static void ds1307_clks_register(struct ds1307 *ds1307)

#endif /* CONFIG_COMMON_CLK */

+#ifdef CONFIG_WATCHDOG_CORE
+static const struct watchdog_info ds1388_wdt_info = {
+ .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+ .identity = "DS1388 watchdog",
+};
+
+static const struct watchdog_ops ds1388_wdt_ops = {
+ .owner = THIS_MODULE,
+ .start = ds1388_wdt_start,
+ .stop = ds1388_wdt_stop,
+ .ping = ds1388_wdt_ping,
+};
+
+static void ds1307_wdt_register(struct ds1307 *ds1307)
+{
+ if (ds1307->type != ds_1388)
+ return;
+
+ ds1307->wdt.info = &ds1388_wdt_info;
+ ds1307->wdt.ops = &ds1388_wdt_ops;
+ ds1307->wdt.max_timeout = 99;
+ ds1307->wdt.min_timeout = 1;
+
+ watchdog_init_timeout(&ds1307->wdt, 99, ds1307->dev);
+ watchdog_set_drvdata(&ds1307->wdt, ds1307);
+ watchdog_register_device(&ds1307->wdt);
+}
+#else
+static void ds1307_wdt_register(struct ds1307 *ds1307)
+{
+}
+#endif /* CONFIG_WATCHDOG_CORE */
+
static const struct regmap_config regmap_config = {
.reg_bits = 8,
.val_bits = 8,
@@ -1865,6 +1961,7 @@ static int ds1307_probe(struct i2c_client *client,

ds1307_hwmon_register(ds1307);
ds1307_clks_register(ds1307);
+ ds1307_wdt_register(ds1307);

return 0;

--
2.25.1
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