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