rtc: ds1347: properly handle oscillator failures

The comment in the probe function stating that it disables oscillator stop
detection and glitch filtering is incorrect as it sets bits 3 and 4 while
it should be setting 5 and 6 to achieve that. Then, it is safe to assume
that the oscillator failure detection is actually enabled.

Properly handle oscillator failures by returning -EINVAL when the time and
date are know to be incorrect and reset the flag when the time is set.

Link: https://lore.kernel.org/r/20191007134724.15505-8-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-ds1347.c b/drivers/rtc/rtc-ds1347.c
index 22a75b01f1ac4940d74a5df6db731deacba5922e..eeaf43586bce7b4fe632f454d09098132b2a8498 100644 (file)
--- a/drivers/rtc/rtc-ds1347.c
+++ b/drivers/rtc/rtc-ds1347.c
@@ -29,6 +29,9 @@
 #define DS1347_STATUS_REG      0x17
 #define DS1347_CLOCK_BURST     0x3F
 
+#define DS1347_NEOSC_BIT       BIT(7)
+#define DS1347_OSF_BIT         BIT(2)
+
 static const struct regmap_range ds1347_ranges[] = {
        {
                .range_min = DS1347_SECONDS_REG,
@@ -44,9 +47,17 @@ static const struct regmap_access_table ds1347_access_table = {
 static int ds1347_read_time(struct device *dev, struct rtc_time *dt)
 {
        struct regmap *map = dev_get_drvdata(dev);
+       unsigned int status;
        int err;
        unsigned char buf[8];
 
+       err = regmap_read(map, DS1347_STATUS_REG, &status);
+       if (err)
+               return err;
+
+       if (status & DS1347_OSF_BIT)
+               return -EINVAL;
+
        err = regmap_bulk_read(map, DS1347_CLOCK_BURST, buf, 8);
        if (err)
                return err;
@@ -66,6 +77,12 @@ static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
 {
        struct regmap *map = dev_get_drvdata(dev);
        unsigned char buf[8];
+       int err;
+
+       err = regmap_update_bits(map, DS1347_STATUS_REG,
+                                DS1347_NEOSC_BIT, DS1347_NEOSC_BIT);
+       if (err)
+               return err;
 
        buf[0] = bin2bcd(dt->tm_sec);
        buf[1] = bin2bcd(dt->tm_min);
@@ -82,7 +99,12 @@ static int ds1347_set_time(struct device *dev, struct rtc_time *dt)
        buf[7] = bin2bcd(0x00);
 
        /* write the rtc settings */
-       return regmap_bulk_write(map, DS1347_CLOCK_BURST, buf, 8);
+       err = regmap_bulk_write(map, DS1347_CLOCK_BURST, buf, 8);
+       if (err)
+               return err;
+
+       return regmap_update_bits(map, DS1347_STATUS_REG,
+                                 DS1347_NEOSC_BIT | DS1347_OSF_BIT, 0);
 }
 
 static const struct rtc_class_ops ds1347_rtc_ops = {
@@ -123,12 +145,6 @@ static int ds1347_probe(struct spi_device *spi)
        data = data & ~(1<<7);
        regmap_write(map, DS1347_CONTROL_REG, data);
 
-       /* Enable the oscillator , disable the oscillator stop flag,
-        and glitch filter to reduce current consumption */
-       regmap_read(map, DS1347_STATUS_REG, &data);
-       data = data & 0x1B;
-       regmap_write(map, DS1347_STATUS_REG, data);
-
        rtc = devm_rtc_allocate_device(&spi->dev);
        if (IS_ERR(rtc))
                return PTR_ERR(rtc);