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linux/drivers/rtc/rtc-pcf8523.c
Baruch Siach ecb4a353d3 rtc: pcf8523: don't return invalid date when battery is low 
The RTC_VL_READ ioctl reports the low battery condition. Still,
pcf8523_rtc_read_time() happily returns invalid dates in this case.
Check the battery health on pcf8523_rtc_read_time() to avoid that.

Reported-by: Erik Čuk <erik.cuk@domel.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
2018-12-11 00:46:53 +01:00

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/*
* Copyright (C) 2012 Avionic Design 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/i2c.h>
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/of.h>
#define DRIVER_NAME "rtc-pcf8523"
#define REG_CONTROL1 0x00
#define REG_CONTROL1_CAP_SEL (1 << 7)
#define REG_CONTROL1_STOP (1 << 5)
#define REG_CONTROL3 0x02
#define REG_CONTROL3_PM_BLD (1 << 7) /* battery low detection disabled */
#define REG_CONTROL3_PM_VDD (1 << 6) /* switch-over disabled */
#define REG_CONTROL3_PM_DSM (1 << 5) /* direct switching mode */
#define REG_CONTROL3_PM_MASK 0xe0
#define REG_CONTROL3_BLF (1 << 2) /* battery low bit, read-only */
#define REG_SECONDS 0x03
#define REG_SECONDS_OS (1 << 7)
#define REG_MINUTES 0x04
#define REG_HOURS 0x05
#define REG_DAYS 0x06
#define REG_WEEKDAYS 0x07
#define REG_MONTHS 0x08
#define REG_YEARS 0x09
#define REG_OFFSET 0x0e
#define REG_OFFSET_MODE BIT(7)
struct pcf8523 {
struct rtc_device *rtc;
};
static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
{
struct i2c_msg msgs[2];
u8 value = 0;
int err;
msgs[0].addr = client->addr;
msgs[0].flags = 0;
msgs[0].len = sizeof(reg);
msgs[0].buf = &reg;
msgs[1].addr = client->addr;
msgs[1].flags = I2C_M_RD;
msgs[1].len = sizeof(value);
msgs[1].buf = &value;
err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
if (err < 0)
return err;
*valuep = value;
return 0;
}
static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
{
u8 buffer[2] = { reg, value };
struct i2c_msg msg;
int err;
msg.addr = client->addr;
msg.flags = 0;
msg.len = sizeof(buffer);
msg.buf = buffer;
err = i2c_transfer(client->adapter, &msg, 1);
if (err < 0)
return err;
return 0;
}
static int pcf8523_voltage_low(struct i2c_client *client)
{
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL3, &value);
if (err < 0)
return err;
return !!(value & REG_CONTROL3_BLF);
}
static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
{
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL1, &value);
if (err < 0)
return err;
if (!high)
value &= ~REG_CONTROL1_CAP_SEL;
else
value |= REG_CONTROL1_CAP_SEL;
err = pcf8523_write(client, REG_CONTROL1, value);
if (err < 0)
return err;
return err;
}
static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
{
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL3, &value);
if (err < 0)
return err;
value = (value & ~REG_CONTROL3_PM_MASK) | pm;
err = pcf8523_write(client, REG_CONTROL3, value);
if (err < 0)
return err;
return 0;
}
static int pcf8523_stop_rtc(struct i2c_client *client)
{
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL1, &value);
if (err < 0)
return err;
value |= REG_CONTROL1_STOP;
err = pcf8523_write(client, REG_CONTROL1, value);
if (err < 0)
return err;
return 0;
}
static int pcf8523_start_rtc(struct i2c_client *client)
{
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL1, &value);
if (err < 0)
return err;
value &= ~REG_CONTROL1_STOP;
err = pcf8523_write(client, REG_CONTROL1, value);
if (err < 0)
return err;
return 0;
}
static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
u8 start = REG_SECONDS, regs[7];
struct i2c_msg msgs[2];
int err;
err = pcf8523_voltage_low(client);
if (err < 0) {
return err;
} else if (err > 0) {
dev_err(dev, "low voltage detected, time is unreliable\n");
return -EINVAL;
}
msgs[0].addr = client->addr;
msgs[0].flags = 0;
msgs[0].len = 1;
msgs[0].buf = &start;
msgs[1].addr = client->addr;
msgs[1].flags = I2C_M_RD;
msgs[1].len = sizeof(regs);
msgs[1].buf = regs;
err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
if (err < 0)
return err;
if (regs[0] & REG_SECONDS_OS)
return -EINVAL;
tm->tm_sec = bcd2bin(regs[0] & 0x7f);
tm->tm_min = bcd2bin(regs[1] & 0x7f);
tm->tm_hour = bcd2bin(regs[2] & 0x3f);
tm->tm_mday = bcd2bin(regs[3] & 0x3f);
tm->tm_wday = regs[4] & 0x7;
tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
tm->tm_year = bcd2bin(regs[6]) + 100;
return 0;
}
static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct i2c_client *client = to_i2c_client(dev);
struct i2c_msg msg;
u8 regs[8];
int err;
/*
* The hardware can only store values between 0 and 99 in it's YEAR
* register (with 99 overflowing to 0 on increment).
* After 2100-02-28 we could start interpreting the year to be in the
* interval [2100, 2199], but there is no path to switch in a smooth way
* because the chip handles YEAR=0x00 (and the out-of-spec
* YEAR=0xa0) as a leap year, but 2100 isn't.
*/
if (tm->tm_year < 100 || tm->tm_year >= 200)
return -EINVAL;
err = pcf8523_stop_rtc(client);
if (err < 0)
return err;
regs[0] = REG_SECONDS;
/* This will purposely overwrite REG_SECONDS_OS */
regs[1] = bin2bcd(tm->tm_sec);
regs[2] = bin2bcd(tm->tm_min);
regs[3] = bin2bcd(tm->tm_hour);
regs[4] = bin2bcd(tm->tm_mday);
regs[5] = tm->tm_wday;
regs[6] = bin2bcd(tm->tm_mon + 1);
regs[7] = bin2bcd(tm->tm_year - 100);
msg.addr = client->addr;
msg.flags = 0;
msg.len = sizeof(regs);
msg.buf = regs;
err = i2c_transfer(client->adapter, &msg, 1);
if (err < 0) {
/*
* If the time cannot be set, restart the RTC anyway. Note
* that errors are ignored if the RTC cannot be started so
* that we have a chance to propagate the original error.
*/
pcf8523_start_rtc(client);
return err;
}
return pcf8523_start_rtc(client);
}
#ifdef CONFIG_RTC_INTF_DEV
static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
unsigned long arg)
{
struct i2c_client *client = to_i2c_client(dev);
int ret;
switch (cmd) {
case RTC_VL_READ:
ret = pcf8523_voltage_low(client);
if (ret < 0)
return ret;
if (copy_to_user((void __user *)arg, &ret, sizeof(int)))
return -EFAULT;
return 0;
default:
return -ENOIOCTLCMD;
}
}
#else
#define pcf8523_rtc_ioctl NULL
#endif
static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
{
struct i2c_client *client = to_i2c_client(dev);
int err;
u8 value;
s8 val;
err = pcf8523_read(client, REG_OFFSET, &value);
if (err < 0)
return err;
/* sign extend the 7-bit offset value */
val = value << 1;
*offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
return 0;
}
static int pcf8523_rtc_set_offset(struct device *dev, long offset)
{
struct i2c_client *client = to_i2c_client(dev);
long reg_m0, reg_m1;
u8 value;
reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
value = reg_m0 & 0x7f;
else
value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
return pcf8523_write(client, REG_OFFSET, value);
}
static const struct rtc_class_ops pcf8523_rtc_ops = {
.read_time = pcf8523_rtc_read_time,
.set_time = pcf8523_rtc_set_time,
.ioctl = pcf8523_rtc_ioctl,
.read_offset = pcf8523_rtc_read_offset,
.set_offset = pcf8523_rtc_set_offset,
};
static int pcf8523_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct pcf8523 *pcf;
int err;
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
return -ENODEV;
pcf = devm_kzalloc(&client->dev, sizeof(*pcf), GFP_KERNEL);
if (!pcf)
return -ENOMEM;
err = pcf8523_select_capacitance(client, true);
if (err < 0)
return err;
err = pcf8523_set_pm(client, 0);
if (err < 0)
return err;
pcf->rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
&pcf8523_rtc_ops, THIS_MODULE);
if (IS_ERR(pcf->rtc))
return PTR_ERR(pcf->rtc);
i2c_set_clientdata(client, pcf);
return 0;
}
static const struct i2c_device_id pcf8523_id[] = {
{ "pcf8523", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, pcf8523_id);
#ifdef CONFIG_OF
static const struct of_device_id pcf8523_of_match[] = {
{ .compatible = "nxp,pcf8523" },
{ }
};
MODULE_DEVICE_TABLE(of, pcf8523_of_match);
#endif
static struct i2c_driver pcf8523_driver = {
.driver = {
.name = DRIVER_NAME,
.of_match_table = of_match_ptr(pcf8523_of_match),
},
.probe = pcf8523_probe,
.id_table = pcf8523_id,
};
module_i2c_driver(pcf8523_driver);
MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
MODULE_LICENSE("GPL v2");
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