1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * ST M48T86 / Dallas DS12887 RTC driver 4 * Copyright (c) 2006 Tower Technologies 5 * 6 * Author: Alessandro Zummo <a.zummo@towertech.it> 7 * 8 * This drivers only supports the clock running in BCD and 24H mode. 9 * If it will be ever adapted to binary and 12H mode, care must be taken 10 * to not introduce bugs. 11 */ 12 13 #include <linux/module.h> 14 #include <linux/mod_devicetable.h> 15 #include <linux/rtc.h> 16 #include <linux/platform_device.h> 17 #include <linux/bcd.h> 18 #include <linux/io.h> 19 20 #define M48T86_SEC 0x00 21 #define M48T86_SECALRM 0x01 22 #define M48T86_MIN 0x02 23 #define M48T86_MINALRM 0x03 24 #define M48T86_HOUR 0x04 25 #define M48T86_HOURALRM 0x05 26 #define M48T86_DOW 0x06 /* 1 = sunday */ 27 #define M48T86_DOM 0x07 28 #define M48T86_MONTH 0x08 /* 1 - 12 */ 29 #define M48T86_YEAR 0x09 /* 0 - 99 */ 30 #define M48T86_A 0x0a 31 #define M48T86_B 0x0b 32 #define M48T86_B_SET BIT(7) 33 #define M48T86_B_DM BIT(2) 34 #define M48T86_B_H24 BIT(1) 35 #define M48T86_C 0x0c 36 #define M48T86_D 0x0d 37 #define M48T86_D_VRT BIT(7) 38 #define M48T86_NVRAM(x) (0x0e + (x)) 39 #define M48T86_NVRAM_LEN 114 40 41 struct m48t86_rtc_info { 42 void __iomem *index_reg; 43 void __iomem *data_reg; 44 struct rtc_device *rtc; 45 }; 46 47 static unsigned char m48t86_readb(struct device *dev, unsigned long addr) 48 { 49 struct m48t86_rtc_info *info = dev_get_drvdata(dev); 50 unsigned char value; 51 52 writeb(addr, info->index_reg); 53 value = readb(info->data_reg); 54 55 return value; 56 } 57 58 static void m48t86_writeb(struct device *dev, 59 unsigned char value, unsigned long addr) 60 { 61 struct m48t86_rtc_info *info = dev_get_drvdata(dev); 62 63 writeb(addr, info->index_reg); 64 writeb(value, info->data_reg); 65 } 66 67 static int m48t86_rtc_read_time(struct device *dev, struct rtc_time *tm) 68 { 69 unsigned char reg; 70 71 reg = m48t86_readb(dev, M48T86_B); 72 73 if (reg & M48T86_B_DM) { 74 /* data (binary) mode */ 75 tm->tm_sec = m48t86_readb(dev, M48T86_SEC); 76 tm->tm_min = m48t86_readb(dev, M48T86_MIN); 77 tm->tm_hour = m48t86_readb(dev, M48T86_HOUR) & 0x3f; 78 tm->tm_mday = m48t86_readb(dev, M48T86_DOM); 79 /* tm_mon is 0-11 */ 80 tm->tm_mon = m48t86_readb(dev, M48T86_MONTH) - 1; 81 tm->tm_year = m48t86_readb(dev, M48T86_YEAR) + 100; 82 tm->tm_wday = m48t86_readb(dev, M48T86_DOW); 83 } else { 84 /* bcd mode */ 85 tm->tm_sec = bcd2bin(m48t86_readb(dev, M48T86_SEC)); 86 tm->tm_min = bcd2bin(m48t86_readb(dev, M48T86_MIN)); 87 tm->tm_hour = bcd2bin(m48t86_readb(dev, M48T86_HOUR) & 88 0x3f); 89 tm->tm_mday = bcd2bin(m48t86_readb(dev, M48T86_DOM)); 90 /* tm_mon is 0-11 */ 91 tm->tm_mon = bcd2bin(m48t86_readb(dev, M48T86_MONTH)) - 1; 92 tm->tm_year = bcd2bin(m48t86_readb(dev, M48T86_YEAR)) + 100; 93 tm->tm_wday = bcd2bin(m48t86_readb(dev, M48T86_DOW)); 94 } 95 96 /* correct the hour if the clock is in 12h mode */ 97 if (!(reg & M48T86_B_H24)) 98 if (m48t86_readb(dev, M48T86_HOUR) & 0x80) 99 tm->tm_hour += 12; 100 101 return 0; 102 } 103 104 static int m48t86_rtc_set_time(struct device *dev, struct rtc_time *tm) 105 { 106 unsigned char reg; 107 108 reg = m48t86_readb(dev, M48T86_B); 109 110 /* update flag and 24h mode */ 111 reg |= M48T86_B_SET | M48T86_B_H24; 112 m48t86_writeb(dev, reg, M48T86_B); 113 114 if (reg & M48T86_B_DM) { 115 /* data (binary) mode */ 116 m48t86_writeb(dev, tm->tm_sec, M48T86_SEC); 117 m48t86_writeb(dev, tm->tm_min, M48T86_MIN); 118 m48t86_writeb(dev, tm->tm_hour, M48T86_HOUR); 119 m48t86_writeb(dev, tm->tm_mday, M48T86_DOM); 120 m48t86_writeb(dev, tm->tm_mon + 1, M48T86_MONTH); 121 m48t86_writeb(dev, tm->tm_year % 100, M48T86_YEAR); 122 m48t86_writeb(dev, tm->tm_wday, M48T86_DOW); 123 } else { 124 /* bcd mode */ 125 m48t86_writeb(dev, bin2bcd(tm->tm_sec), M48T86_SEC); 126 m48t86_writeb(dev, bin2bcd(tm->tm_min), M48T86_MIN); 127 m48t86_writeb(dev, bin2bcd(tm->tm_hour), M48T86_HOUR); 128 m48t86_writeb(dev, bin2bcd(tm->tm_mday), M48T86_DOM); 129 m48t86_writeb(dev, bin2bcd(tm->tm_mon + 1), M48T86_MONTH); 130 m48t86_writeb(dev, bin2bcd(tm->tm_year % 100), M48T86_YEAR); 131 m48t86_writeb(dev, bin2bcd(tm->tm_wday), M48T86_DOW); 132 } 133 134 /* update ended */ 135 reg &= ~M48T86_B_SET; 136 m48t86_writeb(dev, reg, M48T86_B); 137 138 return 0; 139 } 140 141 static int m48t86_rtc_proc(struct device *dev, struct seq_file *seq) 142 { 143 unsigned char reg; 144 145 reg = m48t86_readb(dev, M48T86_B); 146 147 seq_printf(seq, "mode\t\t: %s\n", 148 (reg & M48T86_B_DM) ? "binary" : "bcd"); 149 150 reg = m48t86_readb(dev, M48T86_D); 151 152 seq_printf(seq, "battery\t\t: %s\n", 153 (reg & M48T86_D_VRT) ? "ok" : "exhausted"); 154 155 return 0; 156 } 157 158 static const struct rtc_class_ops m48t86_rtc_ops = { 159 .read_time = m48t86_rtc_read_time, 160 .set_time = m48t86_rtc_set_time, 161 .proc = m48t86_rtc_proc, 162 }; 163 164 static int m48t86_nvram_read(void *priv, unsigned int off, void *buf, 165 size_t count) 166 { 167 struct device *dev = priv; 168 unsigned int i; 169 170 for (i = 0; i < count; i++) 171 ((u8 *)buf)[i] = m48t86_readb(dev, M48T86_NVRAM(off + i)); 172 173 return 0; 174 } 175 176 static int m48t86_nvram_write(void *priv, unsigned int off, void *buf, 177 size_t count) 178 { 179 struct device *dev = priv; 180 unsigned int i; 181 182 for (i = 0; i < count; i++) 183 m48t86_writeb(dev, ((u8 *)buf)[i], M48T86_NVRAM(off + i)); 184 185 return 0; 186 } 187 188 /* 189 * The RTC is an optional feature at purchase time on some Technologic Systems 190 * boards. Verify that it actually exists by checking if the last two bytes 191 * of the NVRAM can be changed. 192 * 193 * This is based on the method used in their rtc7800.c example. 194 */ 195 static bool m48t86_verify_chip(struct platform_device *pdev) 196 { 197 unsigned int offset0 = M48T86_NVRAM(M48T86_NVRAM_LEN - 2); 198 unsigned int offset1 = M48T86_NVRAM(M48T86_NVRAM_LEN - 1); 199 unsigned char tmp0, tmp1; 200 201 tmp0 = m48t86_readb(&pdev->dev, offset0); 202 tmp1 = m48t86_readb(&pdev->dev, offset1); 203 204 m48t86_writeb(&pdev->dev, 0x00, offset0); 205 m48t86_writeb(&pdev->dev, 0x55, offset1); 206 if (m48t86_readb(&pdev->dev, offset1) == 0x55) { 207 m48t86_writeb(&pdev->dev, 0xaa, offset1); 208 if (m48t86_readb(&pdev->dev, offset1) == 0xaa && 209 m48t86_readb(&pdev->dev, offset0) == 0x00) { 210 m48t86_writeb(&pdev->dev, tmp0, offset0); 211 m48t86_writeb(&pdev->dev, tmp1, offset1); 212 213 return true; 214 } 215 } 216 return false; 217 } 218 219 static int m48t86_rtc_probe(struct platform_device *pdev) 220 { 221 struct m48t86_rtc_info *info; 222 unsigned char reg; 223 int err; 224 struct nvmem_config m48t86_nvmem_cfg = { 225 .name = "m48t86_nvram", 226 .word_size = 1, 227 .stride = 1, 228 .size = M48T86_NVRAM_LEN, 229 .reg_read = m48t86_nvram_read, 230 .reg_write = m48t86_nvram_write, 231 .priv = &pdev->dev, 232 }; 233 234 info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL); 235 if (!info) 236 return -ENOMEM; 237 238 info->index_reg = devm_platform_ioremap_resource(pdev, 0); 239 if (IS_ERR(info->index_reg)) 240 return PTR_ERR(info->index_reg); 241 242 info->data_reg = devm_platform_ioremap_resource(pdev, 1); 243 if (IS_ERR(info->data_reg)) 244 return PTR_ERR(info->data_reg); 245 246 dev_set_drvdata(&pdev->dev, info); 247 248 if (!m48t86_verify_chip(pdev)) { 249 dev_info(&pdev->dev, "RTC not present\n"); 250 return -ENODEV; 251 } 252 253 info->rtc = devm_rtc_allocate_device(&pdev->dev); 254 if (IS_ERR(info->rtc)) 255 return PTR_ERR(info->rtc); 256 257 info->rtc->ops = &m48t86_rtc_ops; 258 259 err = devm_rtc_register_device(info->rtc); 260 if (err) 261 return err; 262 263 devm_rtc_nvmem_register(info->rtc, &m48t86_nvmem_cfg); 264 265 /* read battery status */ 266 reg = m48t86_readb(&pdev->dev, M48T86_D); 267 dev_info(&pdev->dev, "battery %s\n", 268 (reg & M48T86_D_VRT) ? "ok" : "exhausted"); 269 270 return 0; 271 } 272 273 static const struct of_device_id m48t86_rtc_of_ids[] = { 274 { .compatible = "st,m48t86" }, 275 { /* sentinel */ } 276 }; 277 MODULE_DEVICE_TABLE(of, m48t86_rtc_of_ids); 278 279 static struct platform_driver m48t86_rtc_platform_driver = { 280 .driver = { 281 .name = "rtc-m48t86", 282 .of_match_table = m48t86_rtc_of_ids, 283 }, 284 .probe = m48t86_rtc_probe, 285 }; 286 287 module_platform_driver(m48t86_rtc_platform_driver); 288 289 MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>"); 290 MODULE_DESCRIPTION("M48T86 RTC driver"); 291 MODULE_LICENSE("GPL"); 292 MODULE_ALIAS("platform:rtc-m48t86"); 293