rtc: m41t93: Add alarm support

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>

diff --git a/drivers/rtc/rtc-m41t93.c b/drivers/rtc/rtc-m41t93.c
index 61e761af56ade6426b1367d5f7db3c0991fa6a79..489bad15695d3e0c3df35f4cdae1af4395220c53 100644 (file)
--- a/drivers/rtc/rtc-m41t93.c
+++ b/drivers/rtc/rtc-m41t93.c
@@ -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;