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linux/drivers/rtc/rtc-pcf2123.c
Joshua Clayton f07fa9242e rtc: pcf2123: avoid resetting the clock if possible 
pcf2123 data sheet recommends a software reset when the chip
is first powered on. This change avoids resetting the chip
every time the driver is loaded, which has some negative effects.

There are several registers including a clock rate adjustment that really
should survive a reload of the driver (or reboot).

In addition, stopping and restarting the clock to verify the chip is
there is not a good thing once the time is set.

According to the data sheet, the seconds register has a 1 in
the high bit when the voltage has gotten low. We check for this
condition, as well as whether the time retrieved from the chip is
valid. We reset the rtc only if the time is not reliable and valid.
This is sufficient for checking for the presence of the chip,
as either all zeros or all 0xff will result in an invalid time/date

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
2016-03-14 17:08:04 +01:00

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/*
* An SPI driver for the Philips PCF2123 RTC
* Copyright 2009 Cyber Switching, Inc.
*
* Author: Chris Verges <chrisv@cyberswitching.com>
* Maintainers: http://www.cyberswitching.com
*
* based on the RS5C348 driver in this same directory.
*
* Thanks to Christian Pellegrin <chripell@fsfe.org> for
* the sysfs contributions to this driver.
*
* 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.
*
* Please note that the CS is active high, so platform data
* should look something like:
*
* static struct spi_board_info ek_spi_devices[] = {
* ...
* {
* .modalias = "rtc-pcf2123",
* .chip_select = 1,
* .controller_data = (void *)AT91_PIN_PA10,
* .max_speed_hz = 1000 * 1000,
* .mode = SPI_CS_HIGH,
* .bus_num = 0,
* },
* ...
*};
*
*/
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/of.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/module.h>
#include <linux/sysfs.h>
#define DRV_VERSION "0.6"
/* REGISTERS */
#define PCF2123_REG_CTRL1 (0x00) /* Control Register 1 */
#define PCF2123_REG_CTRL2 (0x01) /* Control Register 2 */
#define PCF2123_REG_SC (0x02) /* datetime */
#define PCF2123_REG_MN (0x03)
#define PCF2123_REG_HR (0x04)
#define PCF2123_REG_DM (0x05)
#define PCF2123_REG_DW (0x06)
#define PCF2123_REG_MO (0x07)
#define PCF2123_REG_YR (0x08)
#define PCF2123_REG_ALRM_MN (0x09) /* Alarm Registers */
#define PCF2123_REG_ALRM_HR (0x0a)
#define PCF2123_REG_ALRM_DM (0x0b)
#define PCF2123_REG_ALRM_DW (0x0c)
#define PCF2123_REG_OFFSET (0x0d) /* Clock Rate Offset Register */
#define PCF2123_REG_TMR_CLKOUT (0x0e) /* Timer Registers */
#define PCF2123_REG_CTDWN_TMR (0x0f)
/* PCF2123_REG_CTRL1 BITS */
#define CTRL1_CLEAR (0) /* Clear */
#define CTRL1_CORR_INT BIT(1) /* Correction irq enable */
#define CTRL1_12_HOUR BIT(2) /* 12 hour time */
#define CTRL1_SW_RESET (BIT(3) | BIT(4) | BIT(6)) /* Software reset */
#define CTRL1_STOP BIT(5) /* Stop the clock */
#define CTRL1_EXT_TEST BIT(7) /* External clock test mode */
/* PCF2123_REG_CTRL2 BITS */
#define CTRL2_TIE BIT(0) /* Countdown timer irq enable */
#define CTRL2_AIE BIT(1) /* Alarm irq enable */
#define CTRL2_TF BIT(2) /* Countdown timer flag */
#define CTRL2_AF BIT(3) /* Alarm flag */
#define CTRL2_TI_TP BIT(4) /* Irq pin generates pulse */
#define CTRL2_MSF BIT(5) /* Minute or second irq flag */
#define CTRL2_SI BIT(6) /* Second irq enable */
#define CTRL2_MI BIT(7) /* Minute irq enable */
/* PCF2123_REG_SC BITS */
#define OSC_HAS_STOPPED BIT(7) /* Clock has been stopped */
/* PCF2123_REG_ALRM_XX BITS */
#define ALRM_ENABLE BIT(7) /* MN, HR, DM, or DW alarm enable */
/* PCF2123_REG_TMR_CLKOUT BITS */
#define CD_TMR_4096KHZ (0) /* 4096 KHz countdown timer */
#define CD_TMR_64HZ (1) /* 64 Hz countdown timer */
#define CD_TMR_1HZ (2) /* 1 Hz countdown timer */
#define CD_TMR_60th_HZ (3) /* 60th Hz countdown timer */
#define CD_TMR_TE BIT(3) /* Countdown timer enable */
/* PCF2123_REG_OFFSET BITS */
#define OFFSET_SIGN_BIT BIT(6) /* 2's complement sign bit */
#define OFFSET_COARSE BIT(7) /* Coarse mode offset */
/* READ/WRITE ADDRESS BITS */
#define PCF2123_WRITE BIT(4)
#define PCF2123_READ (BIT(4) | BIT(7))
static struct spi_driver pcf2123_driver;
struct pcf2123_sysfs_reg {
struct device_attribute attr;
char name[2];
};
struct pcf2123_plat_data {
struct rtc_device *rtc;
struct pcf2123_sysfs_reg regs[16];
};
/*
* Causes a 30 nanosecond delay to ensure that the PCF2123 chip select
* is released properly after an SPI write. This function should be
* called after EVERY read/write call over SPI.
*/
static inline void pcf2123_delay_trec(void)
{
ndelay(30);
}
static int pcf2123_read(struct device *dev, u8 reg, u8 *rxbuf, size_t size)
{
struct spi_device *spi = to_spi_device(dev);
int ret;
reg |= PCF2123_READ;
ret = spi_write_then_read(spi, &reg, 1, rxbuf, size);
pcf2123_delay_trec();
return ret;
}
static int pcf2123_write(struct device *dev, u8 *txbuf, size_t size)
{
struct spi_device *spi = to_spi_device(dev);
int ret;
txbuf[0] |= PCF2123_WRITE;
ret = spi_write(spi, txbuf, size);
pcf2123_delay_trec();
return ret;
}
static int pcf2123_write_reg(struct device *dev, u8 reg, u8 val)
{
u8 txbuf[2];
txbuf[0] = reg;
txbuf[1] = val;
return pcf2123_write(dev, txbuf, sizeof(txbuf));
}
static ssize_t pcf2123_show(struct device *dev, struct device_attribute *attr,
char *buffer)
{
struct pcf2123_sysfs_reg *r;
u8 rxbuf[1];
unsigned long reg;
int ret;
r = container_of(attr, struct pcf2123_sysfs_reg, attr);
ret = kstrtoul(r->name, 16, &reg);
if (ret)
return ret;
ret = pcf2123_read(dev, reg, rxbuf, 1);
if (ret < 0)
return -EIO;
return sprintf(buffer, "0x%x\n", rxbuf[0]);
}
static ssize_t pcf2123_store(struct device *dev, struct device_attribute *attr,
const char *buffer, size_t count) {
struct pcf2123_sysfs_reg *r;
unsigned long reg;
unsigned long val;
int ret;
r = container_of(attr, struct pcf2123_sysfs_reg, attr);
ret = kstrtoul(r->name, 16, &reg);
if (ret)
return ret;
ret = kstrtoul(buffer, 10, &val);
if (ret)
return ret;
pcf2123_write_reg(dev, reg, val);
if (ret < 0)
return -EIO;
return count;
}
static int pcf2123_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
u8 rxbuf[7];
int ret;
ret = pcf2123_read(dev, PCF2123_REG_SC, rxbuf, sizeof(rxbuf));
if (ret < 0)
return ret;
if (rxbuf[0] & OSC_HAS_STOPPED) {
dev_info(dev, "clock was stopped. Time is not valid\n");
return -EINVAL;
}
tm->tm_sec = bcd2bin(rxbuf[0] & 0x7F);
tm->tm_min = bcd2bin(rxbuf[1] & 0x7F);
tm->tm_hour = bcd2bin(rxbuf[2] & 0x3F); /* rtc hr 0-23 */
tm->tm_mday = bcd2bin(rxbuf[3] & 0x3F);
tm->tm_wday = rxbuf[4] & 0x07;
tm->tm_mon = bcd2bin(rxbuf[5] & 0x1F) - 1; /* rtc mn 1-12 */
tm->tm_year = bcd2bin(rxbuf[6]);
if (tm->tm_year < 70)
tm->tm_year += 100; /* assume we are in 1970...2069 */
dev_dbg(dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
"mday=%d, mon=%d, year=%d, wday=%d\n",
__func__,
tm->tm_sec, tm->tm_min, tm->tm_hour,
tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
return rtc_valid_tm(tm);
}
static int pcf2123_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
u8 txbuf[8];
int ret;
dev_dbg(dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
"mday=%d, mon=%d, year=%d, wday=%d\n",
__func__,
tm->tm_sec, tm->tm_min, tm->tm_hour,
tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
/* Stop the counter first */
ret = pcf2123_write_reg(dev, PCF2123_REG_CTRL1, CTRL1_STOP);
if (ret < 0)
return ret;
/* Set the new time */
txbuf[0] = PCF2123_REG_SC;
txbuf[1] = bin2bcd(tm->tm_sec & 0x7F);
txbuf[2] = bin2bcd(tm->tm_min & 0x7F);
txbuf[3] = bin2bcd(tm->tm_hour & 0x3F);
txbuf[4] = bin2bcd(tm->tm_mday & 0x3F);
txbuf[5] = tm->tm_wday & 0x07;
txbuf[6] = bin2bcd((tm->tm_mon + 1) & 0x1F); /* rtc mn 1-12 */
txbuf[7] = bin2bcd(tm->tm_year < 100 ? tm->tm_year : tm->tm_year - 100);
ret = pcf2123_write(dev, txbuf, sizeof(txbuf));
if (ret < 0)
return ret;
/* Start the counter */
ret = pcf2123_write_reg(dev, PCF2123_REG_CTRL1, CTRL1_CLEAR);
if (ret < 0)
return ret;
return 0;
}
static int pcf2123_reset(struct device *dev)
{
int ret;
u8 rxbuf[2];
ret = pcf2123_write_reg(dev, PCF2123_REG_CTRL1, CTRL1_SW_RESET);
if (ret < 0)
return ret;
/* Stop the counter */
dev_dbg(dev, "stopping RTC\n");
ret = pcf2123_write_reg(dev, PCF2123_REG_CTRL1, CTRL1_STOP);
if (ret < 0)
return ret;
/* See if the counter was actually stopped */
dev_dbg(dev, "checking for presence of RTC\n");
ret = pcf2123_read(dev, PCF2123_REG_CTRL1, rxbuf, sizeof(rxbuf));
if (ret < 0)
return ret;
dev_dbg(dev, "received data from RTC (0x%02X 0x%02X)\n",
rxbuf[0], rxbuf[1]);
if (!(rxbuf[0] & CTRL1_STOP))
return -ENODEV;
/* Start the counter */
ret = pcf2123_write_reg(dev, PCF2123_REG_CTRL1, CTRL1_CLEAR);
if (ret < 0)
return ret;
return 0;
}
static const struct rtc_class_ops pcf2123_rtc_ops = {
.read_time = pcf2123_rtc_read_time,
.set_time = pcf2123_rtc_set_time,
};
static int pcf2123_probe(struct spi_device *spi)
{
struct rtc_device *rtc;
struct rtc_time tm;
struct pcf2123_plat_data *pdata;
int ret, i;
pdata = devm_kzalloc(&spi->dev, sizeof(struct pcf2123_plat_data),
GFP_KERNEL);
if (!pdata)
return -ENOMEM;
spi->dev.platform_data = pdata;
ret = pcf2123_rtc_read_time(&spi->dev, &tm);
if (ret < 0) {
ret = pcf2123_reset(&spi->dev);
if (ret < 0) {
dev_err(&spi->dev, "chip not found\n");
goto kfree_exit;
}
}
dev_info(&spi->dev, "chip found, driver version " DRV_VERSION "\n");
dev_info(&spi->dev, "spiclk %u KHz.\n",
(spi->max_speed_hz + 500) / 1000);
/* Finalize the initialization */
rtc = devm_rtc_device_register(&spi->dev, pcf2123_driver.driver.name,
&pcf2123_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc)) {
dev_err(&spi->dev, "failed to register.\n");
ret = PTR_ERR(rtc);
goto kfree_exit;
}
pdata->rtc = rtc;
for (i = 0; i < 16; i++) {
sysfs_attr_init(&pdata->regs[i].attr.attr);
sprintf(pdata->regs[i].name, "%1x", i);
pdata->regs[i].attr.attr.mode = S_IRUGO | S_IWUSR;
pdata->regs[i].attr.attr.name = pdata->regs[i].name;
pdata->regs[i].attr.show = pcf2123_show;
pdata->regs[i].attr.store = pcf2123_store;
ret = device_create_file(&spi->dev, &pdata->regs[i].attr);
if (ret) {
dev_err(&spi->dev, "Unable to create sysfs %s\n",
pdata->regs[i].name);
goto sysfs_exit;
}
}
return 0;
sysfs_exit:
for (i--; i >= 0; i--)
device_remove_file(&spi->dev, &pdata->regs[i].attr);
kfree_exit:
spi->dev.platform_data = NULL;
return ret;
}
static int pcf2123_remove(struct spi_device *spi)
{
struct pcf2123_plat_data *pdata = dev_get_platdata(&spi->dev);
int i;
if (pdata) {
for (i = 0; i < 16; i++)
if (pdata->regs[i].name[0])
device_remove_file(&spi->dev,
&pdata->regs[i].attr);
}
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id pcf2123_dt_ids[] = {
{ .compatible = "nxp,rtc-pcf2123", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, pcf2123_dt_ids);
#endif
static struct spi_driver pcf2123_driver = {
.driver = {
.name = "rtc-pcf2123",
.of_match_table = of_match_ptr(pcf2123_dt_ids),
},
.probe = pcf2123_probe,
.remove = pcf2123_remove,
};
module_spi_driver(pcf2123_driver);
MODULE_AUTHOR("Chris Verges <chrisv@cyberswitching.com>");
MODULE_DESCRIPTION("NXP PCF2123 RTC driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);
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