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// SPDX-License-Identifier: GPL-2.0-only
/*
* ST M48T86 / Dallas DS12887 RTC driver
* Copyright (c) 2006 Tower Technologies
*
* Author: Alessandro Zummo <a.zummo@towertech.it>
*
* This drivers only supports the clock running in BCD and 24H mode.
* If it will be ever adapted to binary and 12H mode, care must be taken
* to not introduce bugs.
*/
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/bcd.h>
#include <linux/io.h>
#define M48T86_SEC 0x00
#define M48T86_SECALRM 0x01
#define M48T86_MIN 0x02
#define M48T86_MINALRM 0x03
#define M48T86_HOUR 0x04
#define M48T86_HOURALRM 0x05
#define M48T86_DOW 0x06 /* 1 = sunday */
#define M48T86_DOM 0x07
#define M48T86_MONTH 0x08 /* 1 - 12 */
#define M48T86_YEAR 0x09 /* 0 - 99 */
#define M48T86_A 0x0a
#define M48T86_B 0x0b
#define M48T86_B_SET BIT(7)
#define M48T86_B_DM BIT(2)
#define M48T86_B_H24 BIT(1)
#define M48T86_C 0x0c
#define M48T86_D 0x0d
#define M48T86_D_VRT BIT(7)
#define M48T86_NVRAM(x) (0x0e + (x))
#define M48T86_NVRAM_LEN 114
struct m48t86_rtc_info {
void __iomem *index_reg;
void __iomem *data_reg;
struct rtc_device *rtc;
};
static unsigned char m48t86_readb(struct device *dev, unsigned long addr)
{
struct m48t86_rtc_info *info = dev_get_drvdata(dev);
unsigned char value;
writeb(addr, info->index_reg);
value = readb(info->data_reg);
return value;
}
static void m48t86_writeb(struct device *dev,
unsigned char value, unsigned long addr)
{
struct m48t86_rtc_info *info = dev_get_drvdata(dev);
writeb(addr, info->index_reg);
writeb(value, info->data_reg);
}
static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
unsigned char reg;
reg = m48t86_readb(dev, M48T86_B);
if (reg & M48T86_B_DM) {
/* data (binary) mode */
tm->tm_sec = m48t86_readb(dev, M48T86_SEC);
tm->tm_min = m48t86_readb(dev, M48T86_MIN);
tm->tm_hour = m48t86_readb(dev, M48T86_HOUR) & 0x3f;
tm->tm_mday = m48t86_readb(dev, M48T86_DOM);
/* tm_mon is 0-11 */
tm->tm_mon = m48t86_readb(dev, M48T86_MONTH) - 1;
tm->tm_year = m48t86_readb(dev, M48T86_YEAR) + 100;
tm->tm_wday = m48t86_readb(dev, M48T86_DOW);
} else {
/* bcd mode */
tm->tm_sec = bcd2bin(m48t86_readb(dev, M48T86_SEC));
tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN));
tm->tm_hour = bcd2bin(m48t86_readb(dev, M48T86_HOUR) &
0x3f);
tm->tm_mday = bcd2bin(m48t86_readb(dev, M48T86_DOM));
/* tm_mon is 0-11 */
tm->tm_mon = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1;
tm->tm_year = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100;
tm->tm_wday = bcd2bin(m48t86_readb(dev, M48T86_DOW));
}
/* correct the hour if the clock is in 12h mode */
if (!(reg & M48T86_B_H24))
if (m48t86_readb(dev, M48T86_HOUR) & 0x80)
tm->tm_hour += 12;
return 0;
}
static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
unsigned char reg;
reg = m48t86_readb(dev, M48T86_B);
/* update flag and 24h mode */
reg |= M48T86_B_SET | M48T86_B_H24;
m48t86_writeb(dev, reg, M48T86_B);
if (reg & M48T86_B_DM) {
/* data (binary) mode */
m48t86_writeb(dev, tm->tm_sec, M48T86_SEC);
m48t86_writeb(dev, tm->tm_min, M48T86_MIN);
m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR);
m48t86_writeb(dev, tm->tm_mday, M48T86_DOM);
m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH);
m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR);
m48t86_writeb(dev, tm->tm_wday, M48T86_DOW);
} else {
/* bcd mode */
m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC);
m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN);
m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR);
m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM);
m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH);
m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR);
m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW);
}
/* update ended */
reg &= ~M48T86_B_SET;
m48t86_writeb(dev, reg, M48T86_B);
return 0;
}
static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq)
{
unsigned char reg;
reg = m48t86_readb(dev, M48T86_B);
seq_printf(seq, "mode\t\t: %s\n",
(reg & M48T86_B_DM) ? "binary" : "bcd");
reg = m48t86_readb(dev, M48T86_D);
seq_printf(seq, "battery\t\t: %s\n",
(reg & M48T86_D_VRT) ? "ok" : "exhausted");
return 0;
}
static const struct rtc_class_ops m48t86_rtc_ops = {
.read_time = m48t86_rtc_read_time,
.set_time = m48t86_rtc_set_time,
.proc = m48t86_rtc_proc,
};
static int m48t86_nvram_read(void *priv, unsigned int off, void *buf,
size_t count)
{
struct device *dev = priv;
unsigned int i;
for (i = 0; i < count; i++)
((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i));
return 0;
}
static int m48t86_nvram_write(void *priv, unsigned int off, void *buf,
size_t count)
{
struct device *dev = priv;
unsigned int i;
for (i = 0; i < count; i++)
m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i));
return 0;
}
/*
* The RTC is an optional feature at purchase time on some Technologic Systems
* boards. Verify that it actually exists by checking if the last two bytes
* of the NVRAM can be changed.
*
* This is based on the method used in their rtc7800.c example.
*/
static bool m48t86_verify_chip(struct platform_device *pdev)
{
unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2);
unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1);
unsigned char tmp0, tmp1;
tmp0 = m48t86_readb(&pdev->dev, offset0);
tmp1 = m48t86_readb(&pdev->dev, offset1);
m48t86_writeb(&pdev->dev, 0x00, offset0);
m48t86_writeb(&pdev->dev, 0x55, offset1);
if (m48t86_readb(&pdev->dev, offset1) == 0x55) {
m48t86_writeb(&pdev->dev, 0xaa, offset1);
if (m48t86_readb(&pdev->dev, offset1) == 0xaa &&
m48t86_readb(&pdev->dev, offset0) == 0x00) {
m48t86_writeb(&pdev->dev, tmp0, offset0);
m48t86_writeb(&pdev->dev, tmp1, offset1);
return true;
}
}
return false;
}
static int m48t86_rtc_probe(struct platform_device *pdev)
{
struct m48t86_rtc_info *info;
unsigned char reg;
int err;
struct nvmem_config m48t86_nvmem_cfg = {
.name = "m48t86_nvram",
.word_size = 1,
.stride = 1,
.size = M48T86_NVRAM_LEN,
.reg_read = m48t86_nvram_read,
.reg_write = m48t86_nvram_write,
.priv = &pdev->dev,
};
info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
if (!info)
return -ENOMEM;
info->index_reg = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(info->index_reg))
return PTR_ERR(info->index_reg);
info->data_reg = devm_platform_ioremap_resource(pdev, 1);
if (IS_ERR(info->data_reg))
return PTR_ERR(info->data_reg);
dev_set_drvdata(&pdev->dev, info);
if (!m48t86_verify_chip(pdev)) {
dev_info(&pdev->dev, "RTC not present\n");
return -ENODEV;
}
info->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(info->rtc))
return PTR_ERR(info->rtc);
info->rtc->ops = &m48t86_rtc_ops;
err = devm_rtc_register_device(info->rtc);
if (err)
return err;
devm_rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg);
/* read battery status */
reg = m48t86_readb(&pdev->dev, M48T86_D);
dev_info(&pdev->dev, "battery %s\n",
(reg & M48T86_D_VRT) ? "ok" : "exhausted");
return 0;
}
static struct platform_driver m48t86_rtc_platform_driver = {
.driver = {
.name = "rtc-m48t86",
},
.probe = m48t86_rtc_probe,
};
module_platform_driver(m48t86_rtc_platform_driver);
MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
MODULE_DESCRIPTION("M48T86 RTC driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-m48t86");
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