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linux/drivers/rtc/rtc-pcf8523.c
Sam Ravnborg 189927e719 rtc: pcf8523: set xtal load capacitance from DT 
Add support for specifying the xtal load capacitance in the DT node.
The pcf8523 supports xtal load capacitance of 7pF or 12.5pF.
If the rtc has the wrong configuration the time will
drift several hours/week.

The driver use the default value 12.5pF.

The DT may specify either 7000fF or 12500fF.
(The DT uses femto Farad to avoid decimal numbers).
Other values are warned and the driver uses the default value.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
2019-01-22 18:57:08 +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_load_capacitance(struct i2c_client *client)
{
u32 load;
u8 value;
int err;
err = pcf8523_read(client, REG_CONTROL1, &value);
if (err < 0)
return err;
load = 12500;
of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
&load);
switch (load) {
default:
dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
load);
/* fall through */
case 12500:
value |= REG_CONTROL1_CAP_SEL;
break;
case 7000:
value &= ~REG_CONTROL1_CAP_SEL;
break;
}
err = pcf8523_write(client, REG_CONTROL1, value);
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_load_capacitance(client);
if (err < 0)
dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
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" },
{ .compatible = "microcrystal,rv8523" },
{ }
};
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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