diff options
Diffstat (limited to 'drivers/rtc/rtc-m48t86.c')
| -rw-r--r-- | drivers/rtc/rtc-m48t86.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-m48t86.c b/drivers/rtc/rtc-m48t86.c new file mode 100644 index 000000000..481c9525b --- /dev/null +++ b/drivers/rtc/rtc-m48t86.c @@ -0,0 +1,284 @@ +// 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"); |