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rtc: ds1307: add offset sysfs for mt41txx chips. 

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>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Giulio Benetti 2018-07-25 19:26:04 +02:00 committed by Alexandre Belloni
parent 1b4c794fda
commit 79230ff641
1 changed files with 77 additions and 0 deletions
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77
drivers/rtc/rtc-ds1307.c
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@ -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 BIT(7)
# define M41TXX_BIT_FT BIT(6)
# define M41TXX_BIT_CALIB_SIGN BIT(5)
# define M41TXX_M_CALIBRATION GENMASK(4, 0)
/* negative offset step is -2.034ppm */
#define M41TXX_NEG_OFFSET_STEP_PPB 2034
/* positive offset step is +4.068ppm */
#define M41TXX_POS_OFFSET_STEP_PPB 4068
/* Min and max values supported with 'offset' interface by M41TXX */
#define M41TXX_MIN_OFFSET ((-31) * M41TXX_NEG_OFFSET_STEP_PPB)
#define M41TXX_MAX_OFFSET ((31) * M41TXX_POS_OFFSET_STEP_PPB)
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,
@ -228,10 +257,17 @@ 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,
@ -973,6 +1009,47 @@ 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_PPB);
else
*offset = -(val * M41TXX_NEG_OFFSET_STEP_PPB);
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;
if (offset >= 0) {
ctrl_reg = DIV_ROUND_CLOSEST(offset,
M41TXX_POS_OFFSET_STEP_PPB);
ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
} else {
ctrl_reg = DIV_ROUND_CLOSEST(abs(offset),
M41TXX_NEG_OFFSET_STEP_PPB);
}
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,