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Subject[PATCH v4 3/4] rtc: ds1307: add offset sysfs for mt41txx chips.
Date
m41txx chips can hold a calibration value to get correct clock bias.

Add offset handling (ranging between -63ppm and 126ppm) via sysfs.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
V3 => V4:
* use ppm as offset input according to documentation instead of
raw ic offset values.
* use regmap_update_bits instead of regmap_write to update ic registers
* sysfs_remove_group if devm_add_action_or_reset fails
* rtc_device_unregister if ds1307_add_frequency_test fails on m41txx
series

drivers/rtc/rtc-ds1307.c | 81 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 81 insertions(+)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 0ab0c166da83..2797d01bfa1d 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -114,6 +114,20 @@ 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
+
+/* negative offset step is -2.034ppm */
+#define M41TXX_NEG_OFFSET_STEP_PPM 2034
+/* positive offset step is +4.068ppm */
+#define M41TXX_POS_OFFSET_STEP_PPM 4068
+/* Min and max values supported with 'offset' interface by M41TXX */
+#define M41TXX_MIN_OFFSET (((-31) * M41TXX_NEG_OFFSET_STEP_PPM) / 1000)
+#define M41TXX_MAX_OFFSET (((31) * M41TXX_POS_OFFSET_STEP_PPM) / 1000)
+
struct ds1307 {
enum ds_type type;
unsigned long flags;
@@ -146,6 +160,9 @@ 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 +172,8 @@ 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 +191,16 @@ 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 +256,17 @@ 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 +1008,51 @@ 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 * M41TXX_POS_OFFSET_STEP_PPM);
+ else
+ *offset = -(val * M41TXX_NEG_OFFSET_STEP_PPM);
+
+ *offset = DIV_ROUND_CLOSEST(*offset, 1000);
+
+ 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;
+
+ offset *= 1000;
+
+ if (offset >= 0) {
+ ctrl_reg = DIV_ROUND_CLOSEST(offset,
+ M41TXX_POS_OFFSET_STEP_PPM);
+ ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
+ } else {
+ ctrl_reg = DIV_ROUND_CLOSEST(abs(offset),
+ M41TXX_NEG_OFFSET_STEP_PPM);
+ }
+
+ return regmap_update_bits(ds1307->regmap, M41TXX_REG_CONTROL,
+ M41TXX_M_CALIBRATION | M41TXX_BIT_CALIB_SIGN,
+ ctrl_reg);
+}
+
/*----------------------------------------------------------------------*/

static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
--
2.17.0
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