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rtc: m41t93: Add alarm support

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Implement alarm feature for rtc-m41t93 by adding necessary
callbacks - set_alarm, read_alarm and alarm_irq_enable.
Enable support to configure alarm 1 out of 2 alarms present in this rtc.
Support only alarm configuration in this commit. This commit does not
implement alarm irq handling.

Use selftests/rtc/rtctest for testing. Tested by observing IRQ pin
(pin 12 of SOX18 package) on logic analyzer going low after alarm
condition is met.

Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
Link: https://patch.msgid.link/1b272ff1a5392d5eb76e129a4785ac8424763356.1758379856.git.akhilesh@ee.iitb.ac.in
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Akhilesh Patil
2025-09-20 20:32:46 +05:30
committed by Alexandre Belloni
parent d86e868259
commit 5b55ff7cac
1 changed files with 105 additions and 0 deletions
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105
drivers/rtc/rtc-m41t93.c
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@@ -22,6 +22,14 @@
#define M41T93_REG_DAY 5
#define M41T93_REG_MON 6
#define M41T93_REG_YEAR 7
#define M41T93_REG_AL1_MONTH 0xa
#define M41T93_REG_AL1_DATE 0xb
#define M41T93_REG_AL1_HOUR 0xc
#define M41T93_REG_AL1_MIN 0xd
#define M41T93_REG_AL1_SEC 0xe
#define M41T93_BIT_A1IE BIT(7)
#define M41T93_BIT_ABE BIT(5)
#define M41T93_FLAG_AF1 BIT(6)
#define M41T93_REG_ALM_HOUR_HT 0xc
@@ -153,10 +161,107 @@ static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
return ret;
}
static int m41t93_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct m41t93_data *m41t93 = dev_get_drvdata(dev);
int ret;
unsigned int val;
u8 alarm_vals[5] = {0};
ret = regmap_bulk_write(m41t93->regmap, M41T93_REG_AL1_DATE, alarm_vals, 4);
if (ret)
return ret;
/* Set alarm values */
alarm_vals[0] = bin2bcd(alrm->time.tm_mon + 1) & 0x1f;
alarm_vals[1] = bin2bcd(alrm->time.tm_mday) & 0x3f;
alarm_vals[2] = bin2bcd(alrm->time.tm_hour) & 0x3f;
alarm_vals[3] = bin2bcd(alrm->time.tm_min) & 0x7f;
alarm_vals[4] = bin2bcd(alrm->time.tm_sec) & 0x7f;
if (alrm->enabled) {
/* Enable alarm IRQ generation */
alarm_vals[0] |= M41T93_BIT_A1IE | M41T93_BIT_ABE;
}
/* Preserve SQWE bit */
ret = regmap_read(m41t93->regmap, M41T93_REG_AL1_MONTH, &val);
if (ret)
return ret;
alarm_vals[0] |= val & 0x40;
ret = regmap_bulk_write(m41t93->regmap, M41T93_REG_AL1_MONTH,
alarm_vals, sizeof(alarm_vals));
if (ret)
return ret;
/* Device address pointer is now at FLAG register, move it to other location
* to finish setting alarm, as recommended by the datasheet.
* We do read of AL1_MONTH register to achieve this.
*/
ret = regmap_read(m41t93->regmap, M41T93_REG_AL1_MONTH, &val);
if (ret)
return ret;
if (bcd2bin(val & 0x1f) == (alrm->time.tm_mon & 0x1f))
dev_notice(dev, "Alarm set successfully\n");
return 0;
}
static int m41t93_get_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct m41t93_data *m41t93 = dev_get_drvdata(dev);
int ret;
unsigned int val;
u8 alarm_vals[5] = {0};
ret = regmap_bulk_read(m41t93->regmap, M41T93_REG_AL1_MONTH,
alarm_vals, sizeof(alarm_vals));
if (ret)
return ret;
alrm->time.tm_mon = bcd2bin(alarm_vals[0] & 0x1f) - 1;
alrm->time.tm_mday = bcd2bin(alarm_vals[1] & 0x3f);
alrm->time.tm_hour = bcd2bin(alarm_vals[2] & 0x3f);
alrm->time.tm_min = bcd2bin(alarm_vals[3] & 0x7f);
alrm->time.tm_sec = bcd2bin(alarm_vals[4] & 0x7f);
alrm->enabled = !!(alarm_vals[0] & M41T93_BIT_A1IE);
ret = regmap_read(m41t93->regmap, M41T93_REG_FLAGS, &val);
if (ret)
return ret;
alrm->pending = (val & M41T93_FLAG_AF1) && alrm->enabled;
return 0;
}
static int m41t93_alarm_irq_enable(struct device *dev, unsigned int enabled)
{
struct m41t93_data *m41t93 = dev_get_drvdata(dev);
unsigned int val;
int ret;
val = enabled ? M41T93_BIT_A1IE | M41T93_BIT_ABE : 0;
ret = regmap_update_bits(m41t93->regmap, M41T93_REG_AL1_MONTH,
M41T93_BIT_A1IE | M41T93_BIT_ABE, val);
if (ret)
return ret;
return 0;
}
static const struct rtc_class_ops m41t93_rtc_ops = {
.read_time = m41t93_get_time,
.set_time = m41t93_set_time,
.set_alarm = m41t93_set_alarm,
.read_alarm = m41t93_get_alarm,
.alarm_irq_enable = m41t93_alarm_irq_enable,
};
static struct spi_driver m41t93_driver;