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linux/drivers/rtc/rtc-pcf8523.c
Russell King bc3bee0252 rtc: pcf8523: add support for trimming the RTC oscillator 
Add support for reading and writing the RTC offset register, converting
it to the corresponding parts-per-billion value.

When setting the drift, the PCF8523 has two modes: one applies the
adjustment every two hours, the other applies the adjustment every
minute.  We select between these two modes according to which ever
gives the closest PPB value to the one requested.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
2017-10-25 23:05:52 +02:00

379 lines
8.1 KiB
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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_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;
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 rtc_valid_tm(tm);
}
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);
u8 value;
int ret = 0, err;
switch (cmd) {
case RTC_VL_READ:
err = pcf8523_read(client, REG_CONTROL3, &value);
if (err < 0)
return err;
if (value & REG_CONTROL3_BLF)
ret = 1;
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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