github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-27 16:44:58 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

rtc: m41t80: kickstart ocillator upon failure

Browse Source 
The ocillator on the m41t62 (and other chips of this type) needs
a kickstart upon a failure; the RTC read routine will notice the
oscillator failure and fail reads.  This is added in the RTC write
routine; this allows the system to know that the time in the RTC
is accurate.  This is following the procedure described in section
3.11 of  "https://www.st.com/resource/en/datasheet/m41t62.pdf"

Signed-off-by: A. Niyas Ahamed Mydeen <nmydeen@mvista.com>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Link: https://lore.kernel.org/r/20250402120546.336657-2-nmydeen@mvista.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
A. Niyas Ahamed Mydeen 2025-04-02 17:35:46 +05:30 committed by Alexandre Belloni
parent 818b6709e1
commit 1a7ed2fffb
1 changed files with 48 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
drivers/rtc/rtc-m41t80.c
View File

@ -22,6 +22,7 @@
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/string.h>
#include <linux/delay.h>
#ifdef CONFIG_RTC_DRV_M41T80_WDT
#include <linux/fs.h>
#include <linux/ioctl.h>
@ -204,7 +205,7 @@ static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
return flags;
if (flags & M41T80_FLAGS_OF) {
dev_err(&client->dev, "Oscillator failure, data is invalid.\n");
dev_err(&client->dev, "Oscillator failure, time may not be accurate, write time to RTC to fix it.\n");
return -EINVAL;
}
@ -227,21 +228,31 @@ static int m41t80_rtc_read_time(struct device *dev, struct rtc_time *tm)
return 0;
}
static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *in_tm)
{
struct i2c_client *client = to_i2c_client(dev);
struct m41t80_data *clientdata = i2c_get_clientdata(client);
struct rtc_time tm = *in_tm;
unsigned char buf[8];
int err, flags;
time64_t time = 0;
flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
if (flags < 0)
return flags;
if (flags & M41T80_FLAGS_OF) {
/* add 4sec of oscillator stablize time otherwise we are behind 4sec */
time = rtc_tm_to_time64(&tm);
rtc_time64_to_tm(time + 4, &tm);
}
buf[M41T80_REG_SSEC] = 0;
buf[M41T80_REG_SEC] = bin2bcd(tm->tm_sec);
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);
buf[M41T80_REG_WDAY] = tm->tm_wday;
buf[M41T80_REG_SEC] = bin2bcd(tm.tm_sec);
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);
buf[M41T80_REG_WDAY] = tm.tm_wday;
/* If the square wave output is controlled in the weekday register */
if (clientdata->features & M41T80_FEATURE_SQ_ALT) {
@ -260,17 +271,34 @@ static int m41t80_rtc_set_time(struct device *dev, struct rtc_time *tm)
dev_err(&client->dev, "Unable to write to date registers\n");
return err;
}
/* Clear the OF bit of Flags Register */
flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
if (flags < 0)
return flags;
err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS,
flags & ~M41T80_FLAGS_OF);
if (err < 0) {
dev_err(&client->dev, "Unable to write flags register\n");
return err;
if (flags & M41T80_FLAGS_OF) {
/* OF cannot be immediately reset: oscillator has to be restarted. */
dev_warn(&client->dev, "OF bit is still set, kickstarting clock.\n");
err = i2c_smbus_write_byte_data(client, M41T80_REG_SEC, M41T80_SEC_ST);
if (err < 0) {
dev_err(&client->dev, "Can't set ST bit\n");
return err;
}
err = i2c_smbus_write_byte_data(client, M41T80_REG_SEC, flags & ~M41T80_SEC_ST);
if (err < 0) {
dev_err(&client->dev, "Can't clear ST bit\n");
return err;
}
/* oscillator must run for 4sec before we attempt to reset OF bit */
msleep(4000);
/* Clear the OF bit of Flags Register */
err = i2c_smbus_write_byte_data(client, M41T80_REG_FLAGS, flags & ~M41T80_FLAGS_OF);
if (err < 0) {
dev_err(&client->dev, "Unable to write flags register\n");
return err;
}
flags = i2c_smbus_read_byte_data(client, M41T80_REG_FLAGS);
if (flags < 0) {
return flags;
} else if (flags & M41T80_FLAGS_OF) {
dev_err(&client->dev, "Can't clear the OF bit check battery\n");
return err;
}
}
return err;