// 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; info->rtc->nvram_old_abi = true; err = rtc_register_device(info->rtc); if (err) return err; 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");