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path: root/drivers/rtc/rtc-pcf8523.c
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Diffstat (limited to 'drivers/rtc/rtc-pcf8523.c')
-rw-r--r--drivers/rtc/rtc-pcf8523.c40
1 files changed, 40 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
index 28c48b3c1946..c312af0db729 100644
--- a/drivers/rtc/rtc-pcf8523.c
+++ b/drivers/rtc/rtc-pcf8523.c
@@ -35,6 +35,9 @@
#define REG_MONTHS 0x08
#define REG_YEARS 0x09
+#define REG_OFFSET 0x0e
+#define REG_OFFSET_MODE BIT(7)
+
struct pcf8523 {
struct rtc_device *rtc;
};
@@ -272,10 +275,47 @@ static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
#define pcf8523_rtc_ioctl NULL
#endif
+static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ int err;
+ u8 value;
+ s8 val;
+
+ err = pcf8523_read(client, REG_OFFSET, &value);
+ if (err < 0)
+ return err;
+
+ /* sign extend the 7-bit offset value */
+ val = value << 1;
+ *offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
+
+ return 0;
+}
+
+static int pcf8523_rtc_set_offset(struct device *dev, long offset)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ long reg_m0, reg_m1;
+ u8 value;
+
+ reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
+ reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
+
+ if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
+ value = reg_m0 & 0x7f;
+ else
+ value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
+
+ return pcf8523_write(client, REG_OFFSET, value);
+}
+
static const struct rtc_class_ops pcf8523_rtc_ops = {
.read_time = pcf8523_rtc_read_time,
.set_time = pcf8523_rtc_set_time,
.ioctl = pcf8523_rtc_ioctl,
+ .read_offset = pcf8523_rtc_read_offset,
+ .set_offset = pcf8523_rtc_set_offset,
};
static int pcf8523_probe(struct i2c_client *client,