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Subject[PATCH] rtc: Add support for century bits to m41t62 (rv4162) RTC devices
Date
This change adds support for 'century bits' on 4162 family of RTC devices
(from ST or microcrystal), which allow storing time beyond year 2099.

For rv4162 century bits - CB1[7]:CB0[6] are stored in reg6 - 0x6 (MONTH):
CB1 CB0
0 0 (year 2000 - 2099)
0 1 (year 2100 - 2199)
1 0 (year 2200 - 2299)
1 1 (year 2300 - 2399)

The driver has been also adjusted to allow setting time up to year 2399
if the M41T80_FEATURE_CB is set in its DTS/I2C data.

There shall be no functional changes for devices not supporting this
feature. However, other devices - like m41t80 - have different approaches
to handle century information.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
drivers/rtc/rtc-m41t80.c | 56 +++++++++++++++++++++++++++++++---------
1 file changed, 44 insertions(+), 12 deletions(-)

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 9fdc284c943b..5452ab693568 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -68,9 +68,22 @@
#define M41T80_FEATURE_SQ BIT(2) /* Squarewave feature */
#define M41T80_FEATURE_WD BIT(3) /* Extra watchdog resolution */
#define M41T80_FEATURE_SQ_ALT BIT(4) /* RSx bits are in reg 4 */
+#define M41T80_FEATURE_CB BIT(5) /* Century Bits[CB1:CB0] are in reg 6 */
+
+/*
+ * Century bits - CB1[7]:CB0[6] in reg6 (MONTH):
+ * CB1 CB0
+ * 0 0 (year 2000 - 2099)
+ * 0 1 (year 2100 - 2199)
+ * 1 0 (year 2200 - 2299)
+ * 1 1 (year 2300 - 2399)
+ */
+#define M41T80_CB_SHIFT 6 /* CB[0] bit position */
+#define M41T80_CB_MASK 0xc0 /* Century bits mask */

static const struct i2c_device_id m41t80_id[] = {
- { "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
+ { "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT |
+ M41T80_FEATURE_CB},
{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
{ "m41t80", M41T80_FEATURE_SQ },
{ "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
@@ -80,7 +93,8 @@ static const struct i2c_device_id m41t80_id[] = {
{ "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
{ "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
{ "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
- { "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT },
+ { "rv4162", M41T80_FEATURE_SQ | M41T80_FEATURE_WD |
+ M41T80_FEATURE_SQ_ALT | M41T80_FEATURE_CB},
{ }
};
MODULE_DEVICE_TABLE(i2c, m41t80_id);
@@ -88,7 +102,8 @@ MODULE_DEVICE_TABLE(i2c, m41t80_id);
static const struct of_device_id m41t80_of_match[] = {
{
.compatible = "st,m41t62",
- .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT)
+ .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT |
+ M41T80_FEATURE_CB)
},
{
.compatible = "st,m41t65",
@@ -128,16 +143,19 @@ static const struct of_device_id m41t80_of_match[] = {
},
{
.compatible = "microcrystal,rv4162",
- .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+ .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD |
+ M41T80_FEATURE_SQ_ALT | M41T80_FEATURE_CB)
},
/* DT compatibility only, do not use compatibles below: */
{
.compatible = "st,rv4162",
- .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+ .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD |
+ M41T80_FEATURE_SQ_ALT | M41T80_FEATURE_CB)
},
{
.compatible = "rv4162",
- .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD | M41T80_FEATURE_SQ_ALT)
+ .data = (void *)(M41T80_FEATURE_SQ | M41T80_FEATURE_WD |
+ M41T80_FEATURE_SQ_ALT | M41T80_FEATURE_CB)
},
{ }
};
@@ -197,6 +215,7 @@ static irqreturn_t m41t80_handle_irq(int irq, void *dev_id)
static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
+ struct m41t80_data *clientdata = i2c_get_clientdata(client);
unsigned char buf[8];
int err, flags;

@@ -222,9 +241,13 @@ static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
tm->tm_mday = bcd2bin(buf[M41T80_REG_DAY] & 0x3f);
tm->tm_wday = buf[M41T80_REG_WDAY] & 0x07;
tm->tm_mon = bcd2bin(buf[M41T80_REG_MON] & 0x1f) - 1;
-
- /* assume 20YY not 19YY, and ignore the Century Bit */
+ /* assume 20YY not 19YY */
tm->tm_year = bcd2bin(buf[M41T80_REG_YEAR]) + 100;
+
+ if (clientdata->features & M41T80_FEATURE_CB)
+ tm->tm_year += ((buf[M41T80_REG_MON] & M41T80_CB_MASK)
+ >> M41T80_CB_SHIFT) * 100;
+
return 0;
}

@@ -232,10 +255,13 @@ static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
struct m41t80_data *clientdata = i2c_get_clientdata(client);
+ int err, flags, max_year = 199;
unsigned char buf[8];
- int err, flags;

- if (tm->tm_year < 100 || tm->tm_year > 199)
+ if (clientdata->features & M41T80_FEATURE_CB)
+ max_year = 499;
+
+ if (tm->tm_year < 100 || tm->tm_year > max_year)
return -EINVAL;

buf[M41T80_REG_SSEC] = 0;
@@ -243,8 +269,14 @@ static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
buf[M41T80_REG_MIN] = bin2bcd(tm->tm_min);
buf[M41T80_REG_HOUR] = bin2bcd(tm->tm_hour);
buf[M41T80_REG_DAY] = bin2bcd(tm->tm_mday);
- buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
- buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
+ if (clientdata->features & M41T80_FEATURE_CB) {
+ buf[M41T80_REG_YEAR] = bin2bcd((tm->tm_year - 100) % 100);
+ buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1) |
+ (((tm->tm_year - 100) / 100) << M41T80_CB_SHIFT);
+ } else {
+ buf[M41T80_REG_MON] = bin2bcd(tm->tm_mon + 1);
+ buf[M41T80_REG_YEAR] = bin2bcd(tm->tm_year - 100);
+ }
buf[M41T80_REG_WDAY] = tm->tm_wday;

/* If the square wave output is controlled in the weekday register */
--
2.20.1
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