m41txx chips can hold a calibration value to get correct clock bias.
If positive offset is passed, it means adding 512 cycles(@32.768Hz)
every tick(1s).
If negative offset is passed, it means subtracting 256 cycles(@32.768Hz)
every tick(1s).
Add offset handling (ranging between (-31) and 31) via sysfs.
Signed-off-by: Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxx>
---
V1 => V2: changed "calibration" from dt property to rtc sysfs offset
drivers/rtc/rtc-ds1307.c | 70 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)
diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 0ab0c166da83..33895668b363 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -114,6 +114,16 @@ enum ds_type {
# define RX8025_BIT_VDET 0x40
# define RX8025_BIT_XST 0x20
+#define M41TXX_REG_CONTROL 0x07
+# define M41TXX_BIT_OUT 0x80
+# define M41TXX_BIT_FT 0x40
+# define M41TXX_BIT_CALIB_SIGN 0x20
+# define M41TXX_M_CALIBRATION 0x1f
+
+/* Min and max values supported with 'offset' interface by M41TXX */
+#define M41TXX_MIN_OFFSET (-31)
+#define M41TXX_MAX_OFFSET (31)
+
struct ds1307 {
enum ds_type type;
unsigned long flags;
@@ -146,6 +156,9 @@ struct chip_desc {
static int ds1307_get_time(struct device *dev, struct rtc_time *t);
static int ds1307_set_time(struct device *dev, struct rtc_time *t);
+static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t);
+static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t);
+static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled);
static u8 do_trickle_setup_ds1339(struct ds1307 *, u32 ohms, bool diode);
static irqreturn_t rx8130_irq(int irq, void *dev_id);
static int rx8130_read_alarm(struct device *dev, struct rtc_wkalrm *t);
@@ -155,6 +168,8 @@ static irqreturn_t mcp794xx_irq(int irq, void *dev_id);
static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t);
static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t);
static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled);
+static int m41txx_rtc_read_offset(struct device *dev, long *offset);
+static int m41txx_rtc_set_offset(struct device *dev, long offset);
static const struct rtc_class_ops rx8130_rtc_ops = {
.read_time = ds1307_get_time,
@@ -172,6 +187,16 @@ static const struct rtc_class_ops mcp794xx_rtc_ops = {
.alarm_irq_enable = mcp794xx_alarm_irq_enable,
};
+static const struct rtc_class_ops m41txx_rtc_ops = {
+ .read_time = ds1307_get_time,
+ .set_time = ds1307_set_time,
+ .read_alarm = ds1337_read_alarm,
+ .set_alarm = ds1337_set_alarm,
+ .alarm_irq_enable = ds1307_alarm_irq_enable,
+ .read_offset = m41txx_rtc_read_offset,
+ .set_offset = m41txx_rtc_set_offset,
+};
+
static const struct chip_desc chips[last_ds_type] = {
[ds_1307] = {
.nvram_offset = 8,
@@ -227,10 +252,17 @@ static const struct chip_desc chips[last_ds_type] = {
.irq_handler = rx8130_irq,
.rtc_ops = &rx8130_rtc_ops,
},
+ [m41t0] = {
+ .rtc_ops = &m41txx_rtc_ops,
+ },
+ [m41t00] = {
+ .rtc_ops = &m41txx_rtc_ops,
+ },
[m41t11] = {
/* this is battery backed SRAM */
.nvram_offset = 8,
.nvram_size = 56,
+ .rtc_ops = &m41txx_rtc_ops,
},
[mcp794xx] = {
.alarm = 1,
@@ -972,6 +1004,44 @@ static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
enabled ? MCP794XX_BIT_ALM0_EN : 0);
}
+static int m41txx_rtc_read_offset(struct device *dev, long *offset)
+{
+ struct ds1307 *ds1307 = dev_get_drvdata(dev);
+ unsigned int ctrl_reg;
+ u8 val;
+
+ regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
+
+ val = ctrl_reg & M41TXX_M_CALIBRATION;
+
+ /* check if positive */
+ if (ctrl_reg & M41TXX_BIT_CALIB_SIGN)
+ *offset = val;
+ else
+ *offset = -val;
+
+ return 0;
+}
+
+static int m41txx_rtc_set_offset(struct device *dev, long offset)
+{
+ struct ds1307 *ds1307 = dev_get_drvdata(dev);
+ unsigned int ctrl_reg;
+
+ if ((offset < M41TXX_MIN_OFFSET) || (offset > M41TXX_MAX_OFFSET))
+ return -ERANGE;
+
+ regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
+
+ ctrl_reg &= ~M41TXX_M_CALIBRATION;
+ ctrl_reg |= abs(offset) & M41TXX_M_CALIBRATION;
+
+ if (offset >= 0)
+ ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
+
+ return regmap_write(ds1307->regmap, M41TXX_REG_CONTROL, ctrl_reg);
+}
+
/*----------------------------------------------------------------------*/
static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
--
2.17.0
--
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