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linux/drivers/rtc/rtc-m41t93.c
Nikolaus Voss bcffb10f28 drivers/rtc/rtc-m41t93.c: don't let get_time() reset M41T93_FLAG_OF
If the rtc reports the time might be invalid due to oscillator failure,
M41T93_FLAG_OF flag must not be reset by get_time() as the read operation
doesn't make the time valid.

Without this patch, only the first get_time() reported an invalid time,
the second get_time() reported a valid time althought the reported time is
probably wrong due to oscillator failure.

Instead of resetting in get_time(), with this patch M41T93_FLAG_OF is
reset in set_time() when a valid time is to be written.

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-29 16:22:33 -07:00

223 lines
5.7 KiB
C

/*
*
* Driver for ST M41T93 SPI RTC
*
* (c) 2010 Nikolaus Voss, Weinmann Medical GmbH
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/bcd.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#define M41T93_REG_SSEC 0
#define M41T93_REG_ST_SEC 1
#define M41T93_REG_MIN 2
#define M41T93_REG_CENT_HOUR 3
#define M41T93_REG_WDAY 4
#define M41T93_REG_DAY 5
#define M41T93_REG_MON 6
#define M41T93_REG_YEAR 7
#define M41T93_REG_ALM_HOUR_HT 0xc
#define M41T93_REG_FLAGS 0xf
#define M41T93_FLAG_ST (1 << 7)
#define M41T93_FLAG_OF (1 << 2)
#define M41T93_FLAG_BL (1 << 4)
#define M41T93_FLAG_HT (1 << 6)
static inline int m41t93_set_reg(struct spi_device *spi, u8 addr, u8 data)
{
u8 buf[2];
/* MSB must be '1' to write */
buf[0] = addr | 0x80;
buf[1] = data;
return spi_write(spi, buf, sizeof(buf));
}
static int m41t93_set_time(struct device *dev, struct rtc_time *tm)
{
struct spi_device *spi = to_spi_device(dev);
int tmp;
u8 buf[9] = {0x80}; /* write cmd + 8 data bytes */
u8 * const data = &buf[1]; /* ptr to first data byte */
dev_dbg(dev, "%s secs=%d, mins=%d, "
"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
"write", tm->tm_sec, tm->tm_min,
tm->tm_hour, tm->tm_mday,
tm->tm_mon, tm->tm_year, tm->tm_wday);
if (tm->tm_year < 100) {
dev_warn(&spi->dev, "unsupported date (before 2000-01-01).\n");
return -EINVAL;
}
tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
if (tmp < 0)
return tmp;
if (tmp & M41T93_FLAG_OF) {
dev_warn(&spi->dev, "OF bit is set, resetting.\n");
m41t93_set_reg(spi, M41T93_REG_FLAGS, tmp & ~M41T93_FLAG_OF);
tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
if (tmp < 0) {
return tmp;
} else if (tmp & M41T93_FLAG_OF) {
/* OF cannot be immediately reset: oscillator has to be
* restarted. */
u8 reset_osc = buf[M41T93_REG_ST_SEC] | M41T93_FLAG_ST;
dev_warn(&spi->dev,
"OF bit is still set, kickstarting clock.\n");
m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
reset_osc &= ~M41T93_FLAG_ST;
m41t93_set_reg(spi, M41T93_REG_ST_SEC, reset_osc);
}
}
data[M41T93_REG_SSEC] = 0;
data[M41T93_REG_ST_SEC] = bin2bcd(tm->tm_sec);
data[M41T93_REG_MIN] = bin2bcd(tm->tm_min);
data[M41T93_REG_CENT_HOUR] = bin2bcd(tm->tm_hour) |
((tm->tm_year/100-1) << 6);
data[M41T93_REG_DAY] = bin2bcd(tm->tm_mday);
data[M41T93_REG_WDAY] = bin2bcd(tm->tm_wday + 1);
data[M41T93_REG_MON] = bin2bcd(tm->tm_mon + 1);
data[M41T93_REG_YEAR] = bin2bcd(tm->tm_year % 100);
return spi_write(spi, buf, sizeof(buf));
}
static int m41t93_get_time(struct device *dev, struct rtc_time *tm)
{
struct spi_device *spi = to_spi_device(dev);
const u8 start_addr = 0;
u8 buf[8];
int century_after_1900;
int tmp;
int ret = 0;
/* Check status of clock. Two states must be considered:
1. halt bit (HT) is set: the clock is running but update of readout
registers has been disabled due to power failure. This is normal
case after poweron. Time is valid after resetting HT bit.
2. oscillator fail bit (OF) is set: time is invalid.
*/
tmp = spi_w8r8(spi, M41T93_REG_ALM_HOUR_HT);
if (tmp < 0)
return tmp;
if (tmp & M41T93_FLAG_HT) {
dev_dbg(&spi->dev, "HT bit is set, reenable clock update.\n");
m41t93_set_reg(spi, M41T93_REG_ALM_HOUR_HT,
tmp & ~M41T93_FLAG_HT);
}
tmp = spi_w8r8(spi, M41T93_REG_FLAGS);
if (tmp < 0)
return tmp;
if (tmp & M41T93_FLAG_OF) {
ret = -EINVAL;
dev_warn(&spi->dev, "OF bit is set, write time to restart.\n");
}
if (tmp & M41T93_FLAG_BL)
dev_warn(&spi->dev, "BL bit is set, replace battery.\n");
/* read actual time/date */
tmp = spi_write_then_read(spi, &start_addr, 1, buf, sizeof(buf));
if (tmp < 0)
return tmp;
tm->tm_sec = bcd2bin(buf[M41T93_REG_ST_SEC]);
tm->tm_min = bcd2bin(buf[M41T93_REG_MIN]);
tm->tm_hour = bcd2bin(buf[M41T93_REG_CENT_HOUR] & 0x3f);
tm->tm_mday = bcd2bin(buf[M41T93_REG_DAY]);
tm->tm_mon = bcd2bin(buf[M41T93_REG_MON]) - 1;
tm->tm_wday = bcd2bin(buf[M41T93_REG_WDAY] & 0x0f) - 1;
century_after_1900 = (buf[M41T93_REG_CENT_HOUR] >> 6) + 1;
tm->tm_year = bcd2bin(buf[M41T93_REG_YEAR]) + century_after_1900 * 100;
dev_dbg(dev, "%s secs=%d, mins=%d, "
"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
"read", tm->tm_sec, tm->tm_min,
tm->tm_hour, tm->tm_mday,
tm->tm_mon, tm->tm_year, tm->tm_wday);
return ret < 0 ? ret : rtc_valid_tm(tm);
}
static const struct rtc_class_ops m41t93_rtc_ops = {
.read_time = m41t93_get_time,
.set_time = m41t93_set_time,
};
static struct spi_driver m41t93_driver;
static int __devinit m41t93_probe(struct spi_device *spi)
{
struct rtc_device *rtc;
int res;
spi->bits_per_word = 8;
spi_setup(spi);
res = spi_w8r8(spi, M41T93_REG_WDAY);
if (res < 0 || (res & 0xf8) != 0) {
dev_err(&spi->dev, "not found 0x%x.\n", res);
return -ENODEV;
}
rtc = rtc_device_register(m41t93_driver.driver.name,
&spi->dev, &m41t93_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc))
return PTR_ERR(rtc);
dev_set_drvdata(&spi->dev, rtc);
return 0;
}
static int __devexit m41t93_remove(struct spi_device *spi)
{
struct rtc_device *rtc = spi_get_drvdata(spi);
if (rtc)
rtc_device_unregister(rtc);
return 0;
}
static struct spi_driver m41t93_driver = {
.driver = {
.name = "rtc-m41t93",
.owner = THIS_MODULE,
},
.probe = m41t93_probe,
.remove = __devexit_p(m41t93_remove),
};
module_spi_driver(m41t93_driver);
MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
MODULE_DESCRIPTION("Driver for ST M41T93 SPI RTC");
MODULE_LICENSE("GPL");
MODULE_ALIAS("spi:rtc-m41t93");