1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * "RTT as Real Time Clock" driver for AT91SAM9 SoC family 4 * 5 * (C) 2007 Michel Benoit 6 * 7 * Based on rtc-at91rm9200.c by Rick Bronson 8 */ 9 10 #include <linux/clk.h> 11 #include <linux/interrupt.h> 12 #include <linux/ioctl.h> 13 #include <linux/io.h> 14 #include <linux/kernel.h> 15 #include <linux/mfd/syscon.h> 16 #include <linux/module.h> 17 #include <linux/of.h> 18 #include <linux/platform_device.h> 19 #include <linux/regmap.h> 20 #include <linux/rtc.h> 21 #include <linux/slab.h> 22 #include <linux/suspend.h> 23 #include <linux/time.h> 24 25 /* 26 * This driver uses two configurable hardware resources that live in the 27 * AT91SAM9 backup power domain (intended to be powered at all times) 28 * to implement the Real Time Clock interfaces 29 * 30 * - A "Real-time Timer" (RTT) counts up in seconds from a base time. 31 * We can't assign the counter value (CRTV) ... but we can reset it. 32 * 33 * - One of the "General Purpose Backup Registers" (GPBRs) holds the 34 * base time, normally an offset from the beginning of the POSIX 35 * epoch (1970-Jan-1 00:00:00 UTC). Some systems also include the 36 * local timezone's offset. 37 * 38 * The RTC's value is the RTT counter plus that offset. The RTC's alarm 39 * is likewise a base (ALMV) plus that offset. 40 * 41 * Not all RTTs will be used as RTCs; some systems have multiple RTTs to 42 * choose from, or a "real" RTC module. All systems have multiple GPBR 43 * registers available, likewise usable for more than "RTC" support. 44 */ 45 46 #define AT91_RTT_MR 0x00 /* Real-time Mode Register */ 47 #define AT91_RTT_RTPRES (0xffff << 0) /* Timer Prescaler Value */ 48 #define AT91_RTT_ALMIEN BIT(16) /* Alarm Interrupt Enable */ 49 #define AT91_RTT_RTTINCIEN BIT(17) /* Increment Interrupt Enable */ 50 #define AT91_RTT_RTTRST BIT(18) /* Timer Restart */ 51 52 #define AT91_RTT_AR 0x04 /* Real-time Alarm Register */ 53 #define AT91_RTT_ALMV (0xffffffff) /* Alarm Value */ 54 55 #define AT91_RTT_VR 0x08 /* Real-time Value Register */ 56 #define AT91_RTT_CRTV (0xffffffff) /* Current Real-time Value */ 57 58 #define AT91_RTT_SR 0x0c /* Real-time Status Register */ 59 #define AT91_RTT_ALMS BIT(0) /* Alarm Status */ 60 #define AT91_RTT_RTTINC BIT(1) /* Timer Increment */ 61 62 /* 63 * We store ALARM_DISABLED in ALMV to record that no alarm is set. 64 * It's also the reset value for that field. 65 */ 66 #define ALARM_DISABLED ((u32)~0) 67 68 struct sam9_rtc { 69 void __iomem *rtt; 70 struct rtc_device *rtcdev; 71 u32 imr; 72 struct regmap *gpbr; 73 unsigned int gpbr_offset; 74 int irq; 75 struct clk *sclk; 76 bool suspended; 77 unsigned long events; 78 spinlock_t lock; 79 }; 80 81 #define rtt_readl(rtc, field) \ 82 readl((rtc)->rtt + AT91_RTT_ ## field) 83 #define rtt_writel(rtc, field, val) \ 84 writel((val), (rtc)->rtt + AT91_RTT_ ## field) 85 86 static inline unsigned int gpbr_readl(struct sam9_rtc *rtc) 87 { 88 unsigned int val; 89 90 regmap_read(rtc->gpbr, rtc->gpbr_offset, &val); 91 92 return val; 93 } 94 95 static inline void gpbr_writel(struct sam9_rtc *rtc, unsigned int val) 96 { 97 regmap_write(rtc->gpbr, rtc->gpbr_offset, val); 98 } 99 100 /* 101 * Read current time and date in RTC 102 */ 103 static int at91_rtc_readtime(struct device *dev, struct rtc_time *tm) 104 { 105 struct sam9_rtc *rtc = dev_get_drvdata(dev); 106 u32 secs, secs2; 107 u32 offset; 108 109 /* read current time offset */ 110 offset = gpbr_readl(rtc); 111 if (offset == 0) 112 return -EILSEQ; 113 114 /* reread the counter to help sync the two clock domains */ 115 secs = rtt_readl(rtc, VR); 116 secs2 = rtt_readl(rtc, VR); 117 if (secs != secs2) 118 secs = rtt_readl(rtc, VR); 119 120 rtc_time64_to_tm(offset + secs, tm); 121 122 dev_dbg(dev, "%s: %ptR\n", __func__, tm); 123 124 return 0; 125 } 126 127 /* 128 * Set current time and date in RTC 129 */ 130 static int at91_rtc_settime(struct device *dev, struct rtc_time *tm) 131 { 132 struct sam9_rtc *rtc = dev_get_drvdata(dev); 133 u32 offset, alarm, mr; 134 unsigned long secs; 135 136 dev_dbg(dev, "%s: %ptR\n", __func__, tm); 137 138 secs = rtc_tm_to_time64(tm); 139 140 mr = rtt_readl(rtc, MR); 141 142 /* disable interrupts */ 143 rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)); 144 145 /* read current time offset */ 146 offset = gpbr_readl(rtc); 147 148 /* store the new base time in a battery backup register */ 149 secs += 1; 150 gpbr_writel(rtc, secs); 151 152 /* adjust the alarm time for the new base */ 153 alarm = rtt_readl(rtc, AR); 154 if (alarm != ALARM_DISABLED) { 155 if (offset > secs) { 156 /* time jumped backwards, increase time until alarm */ 157 alarm += (offset - secs); 158 } else if ((alarm + offset) > secs) { 159 /* time jumped forwards, decrease time until alarm */ 160 alarm -= (secs - offset); 161 } else { 162 /* time jumped past the alarm, disable alarm */ 163 alarm = ALARM_DISABLED; 164 mr &= ~AT91_RTT_ALMIEN; 165 } 166 rtt_writel(rtc, AR, alarm); 167 } 168 169 /* reset the timer, and re-enable interrupts */ 170 rtt_writel(rtc, MR, mr | AT91_RTT_RTTRST); 171 172 return 0; 173 } 174 175 static int at91_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm) 176 { 177 struct sam9_rtc *rtc = dev_get_drvdata(dev); 178 struct rtc_time *tm = &alrm->time; 179 u32 alarm = rtt_readl(rtc, AR); 180 u32 offset; 181 182 offset = gpbr_readl(rtc); 183 if (offset == 0) 184 return -EILSEQ; 185 186 memset(alrm, 0, sizeof(*alrm)); 187 if (alarm != ALARM_DISABLED) { 188 rtc_time64_to_tm(offset + alarm, tm); 189 190 dev_dbg(dev, "%s: %ptR\n", __func__, tm); 191 192 if (rtt_readl(rtc, MR) & AT91_RTT_ALMIEN) 193 alrm->enabled = 1; 194 } 195 196 return 0; 197 } 198 199 static int at91_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm) 200 { 201 struct sam9_rtc *rtc = dev_get_drvdata(dev); 202 struct rtc_time *tm = &alrm->time; 203 unsigned long secs; 204 u32 offset; 205 u32 mr; 206 207 secs = rtc_tm_to_time64(tm); 208 209 offset = gpbr_readl(rtc); 210 if (offset == 0) { 211 /* time is not set */ 212 return -EILSEQ; 213 } 214 mr = rtt_readl(rtc, MR); 215 rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN); 216 217 /* alarm in the past? finish and leave disabled */ 218 if (secs <= offset) { 219 rtt_writel(rtc, AR, ALARM_DISABLED); 220 return 0; 221 } 222 223 /* else set alarm and maybe enable it */ 224 rtt_writel(rtc, AR, secs - offset); 225 if (alrm->enabled) 226 rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN); 227 228 dev_dbg(dev, "%s: %ptR\n", __func__, tm); 229 230 return 0; 231 } 232 233 static int at91_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled) 234 { 235 struct sam9_rtc *rtc = dev_get_drvdata(dev); 236 u32 mr = rtt_readl(rtc, MR); 237 238 dev_dbg(dev, "alarm_irq_enable: enabled=%08x, mr %08x\n", enabled, mr); 239 if (enabled) 240 rtt_writel(rtc, MR, mr | AT91_RTT_ALMIEN); 241 else 242 rtt_writel(rtc, MR, mr & ~AT91_RTT_ALMIEN); 243 return 0; 244 } 245 246 /* 247 * Provide additional RTC information in /proc/driver/rtc 248 */ 249 static int at91_rtc_proc(struct device *dev, struct seq_file *seq) 250 { 251 struct sam9_rtc *rtc = dev_get_drvdata(dev); 252 u32 mr = rtt_readl(rtc, MR); 253 254 seq_printf(seq, "update_IRQ\t: %s\n", 255 (mr & AT91_RTT_RTTINCIEN) ? "yes" : "no"); 256 return 0; 257 } 258 259 static irqreturn_t at91_rtc_cache_events(struct sam9_rtc *rtc) 260 { 261 u32 sr, mr; 262 263 /* Shared interrupt may be for another device. Note: reading 264 * SR clears it, so we must only read it in this irq handler! 265 */ 266 mr = rtt_readl(rtc, MR) & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN); 267 sr = rtt_readl(rtc, SR) & (mr >> 16); 268 if (!sr) 269 return IRQ_NONE; 270 271 /* alarm status */ 272 if (sr & AT91_RTT_ALMS) 273 rtc->events |= (RTC_AF | RTC_IRQF); 274 275 /* timer update/increment */ 276 if (sr & AT91_RTT_RTTINC) 277 rtc->events |= (RTC_UF | RTC_IRQF); 278 279 return IRQ_HANDLED; 280 } 281 282 static void at91_rtc_flush_events(struct sam9_rtc *rtc) 283 { 284 if (!rtc->events) 285 return; 286 287 rtc_update_irq(rtc->rtcdev, 1, rtc->events); 288 rtc->events = 0; 289 290 pr_debug("%s: num=%ld, events=0x%02lx\n", __func__, 291 rtc->events >> 8, rtc->events & 0x000000FF); 292 } 293 294 /* 295 * IRQ handler for the RTC 296 */ 297 static irqreturn_t at91_rtc_interrupt(int irq, void *_rtc) 298 { 299 struct sam9_rtc *rtc = _rtc; 300 int ret; 301 302 spin_lock(&rtc->lock); 303 304 ret = at91_rtc_cache_events(rtc); 305 306 /* We're called in suspended state */ 307 if (rtc->suspended) { 308 /* Mask irqs coming from this peripheral */ 309 rtt_writel(rtc, MR, 310 rtt_readl(rtc, MR) & 311 ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)); 312 /* Trigger a system wakeup */ 313 pm_system_wakeup(); 314 } else { 315 at91_rtc_flush_events(rtc); 316 } 317 318 spin_unlock(&rtc->lock); 319 320 return ret; 321 } 322 323 static const struct rtc_class_ops at91_rtc_ops = { 324 .read_time = at91_rtc_readtime, 325 .set_time = at91_rtc_settime, 326 .read_alarm = at91_rtc_readalarm, 327 .set_alarm = at91_rtc_setalarm, 328 .proc = at91_rtc_proc, 329 .alarm_irq_enable = at91_rtc_alarm_irq_enable, 330 }; 331 332 /* 333 * Initialize and install RTC driver 334 */ 335 static int at91_rtc_probe(struct platform_device *pdev) 336 { 337 struct sam9_rtc *rtc; 338 int ret, irq; 339 u32 mr; 340 unsigned int sclk_rate; 341 struct of_phandle_args args; 342 343 irq = platform_get_irq(pdev, 0); 344 if (irq < 0) 345 return irq; 346 347 rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL); 348 if (!rtc) 349 return -ENOMEM; 350 351 spin_lock_init(&rtc->lock); 352 rtc->irq = irq; 353 354 /* platform setup code should have handled this; sigh */ 355 if (!device_can_wakeup(&pdev->dev)) 356 device_init_wakeup(&pdev->dev, 1); 357 358 platform_set_drvdata(pdev, rtc); 359 360 rtc->rtt = devm_platform_ioremap_resource(pdev, 0); 361 if (IS_ERR(rtc->rtt)) 362 return PTR_ERR(rtc->rtt); 363 364 ret = of_parse_phandle_with_fixed_args(pdev->dev.of_node, 365 "atmel,rtt-rtc-time-reg", 1, 0, 366 &args); 367 if (ret) 368 return ret; 369 370 rtc->gpbr = syscon_node_to_regmap(args.np); 371 rtc->gpbr_offset = args.args[0]; 372 if (IS_ERR(rtc->gpbr)) { 373 dev_err(&pdev->dev, "failed to retrieve gpbr regmap, aborting.\n"); 374 return -ENOMEM; 375 } 376 377 rtc->sclk = devm_clk_get(&pdev->dev, NULL); 378 if (IS_ERR(rtc->sclk)) 379 return PTR_ERR(rtc->sclk); 380 381 ret = clk_prepare_enable(rtc->sclk); 382 if (ret) { 383 dev_err(&pdev->dev, "Could not enable slow clock\n"); 384 return ret; 385 } 386 387 sclk_rate = clk_get_rate(rtc->sclk); 388 if (!sclk_rate || sclk_rate > AT91_RTT_RTPRES) { 389 dev_err(&pdev->dev, "Invalid slow clock rate\n"); 390 ret = -EINVAL; 391 goto err_clk; 392 } 393 394 mr = rtt_readl(rtc, MR); 395 396 /* unless RTT is counting at 1 Hz, re-initialize it */ 397 if ((mr & AT91_RTT_RTPRES) != sclk_rate) { 398 mr = AT91_RTT_RTTRST | (sclk_rate & AT91_RTT_RTPRES); 399 gpbr_writel(rtc, 0); 400 } 401 402 /* disable all interrupts (same as on shutdown path) */ 403 mr &= ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN); 404 rtt_writel(rtc, MR, mr); 405 406 rtc->rtcdev = devm_rtc_allocate_device(&pdev->dev); 407 if (IS_ERR(rtc->rtcdev)) { 408 ret = PTR_ERR(rtc->rtcdev); 409 goto err_clk; 410 } 411 412 rtc->rtcdev->ops = &at91_rtc_ops; 413 rtc->rtcdev->range_max = U32_MAX; 414 415 /* register irq handler after we know what name we'll use */ 416 ret = devm_request_irq(&pdev->dev, rtc->irq, at91_rtc_interrupt, 417 IRQF_SHARED | IRQF_COND_SUSPEND, 418 dev_name(&rtc->rtcdev->dev), rtc); 419 if (ret) { 420 dev_dbg(&pdev->dev, "can't share IRQ %d?\n", rtc->irq); 421 goto err_clk; 422 } 423 424 /* NOTE: sam9260 rev A silicon has a ROM bug which resets the 425 * RTT on at least some reboots. If you have that chip, you must 426 * initialize the time from some external source like a GPS, wall 427 * clock, discrete RTC, etc 428 */ 429 430 if (gpbr_readl(rtc) == 0) 431 dev_warn(&pdev->dev, "%s: SET TIME!\n", 432 dev_name(&rtc->rtcdev->dev)); 433 434 return devm_rtc_register_device(rtc->rtcdev); 435 436 err_clk: 437 clk_disable_unprepare(rtc->sclk); 438 439 return ret; 440 } 441 442 /* 443 * Disable and remove the RTC driver 444 */ 445 static void at91_rtc_remove(struct platform_device *pdev) 446 { 447 struct sam9_rtc *rtc = platform_get_drvdata(pdev); 448 u32 mr = rtt_readl(rtc, MR); 449 450 /* disable all interrupts */ 451 rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN)); 452 453 clk_disable_unprepare(rtc->sclk); 454 } 455 456 static void at91_rtc_shutdown(struct platform_device *pdev) 457 { 458 struct sam9_rtc *rtc = platform_get_drvdata(pdev); 459 u32 mr = rtt_readl(rtc, MR); 460 461 rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN); 462 rtt_writel(rtc, MR, mr & ~rtc->imr); 463 } 464 465 #ifdef CONFIG_PM_SLEEP 466 467 /* AT91SAM9 RTC Power management control */ 468 469 static int at91_rtc_suspend(struct device *dev) 470 { 471 struct sam9_rtc *rtc = dev_get_drvdata(dev); 472 u32 mr = rtt_readl(rtc, MR); 473 474 /* 475 * This IRQ is shared with DBGU and other hardware which isn't 476 * necessarily a wakeup event source. 477 */ 478 rtc->imr = mr & (AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN); 479 if (rtc->imr) { 480 if (device_may_wakeup(dev) && (mr & AT91_RTT_ALMIEN)) { 481 unsigned long flags; 482 483 enable_irq_wake(rtc->irq); 484 spin_lock_irqsave(&rtc->lock, flags); 485 rtc->suspended = true; 486 spin_unlock_irqrestore(&rtc->lock, flags); 487 /* don't let RTTINC cause wakeups */ 488 if (mr & AT91_RTT_RTTINCIEN) 489 rtt_writel(rtc, MR, mr & ~AT91_RTT_RTTINCIEN); 490 } else { 491 rtt_writel(rtc, MR, mr & ~rtc->imr); 492 } 493 } 494 495 return 0; 496 } 497 498 static int at91_rtc_resume(struct device *dev) 499 { 500 struct sam9_rtc *rtc = dev_get_drvdata(dev); 501 u32 mr; 502 503 if (rtc->imr) { 504 unsigned long flags; 505 506 if (device_may_wakeup(dev)) 507 disable_irq_wake(rtc->irq); 508 mr = rtt_readl(rtc, MR); 509 rtt_writel(rtc, MR, mr | rtc->imr); 510 511 spin_lock_irqsave(&rtc->lock, flags); 512 rtc->suspended = false; 513 at91_rtc_cache_events(rtc); 514 at91_rtc_flush_events(rtc); 515 spin_unlock_irqrestore(&rtc->lock, flags); 516 } 517 518 return 0; 519 } 520 #endif 521 522 static SIMPLE_DEV_PM_OPS(at91_rtc_pm_ops, at91_rtc_suspend, at91_rtc_resume); 523 524 static const struct of_device_id at91_rtc_dt_ids[] = { 525 { .compatible = "atmel,at91sam9260-rtt" }, 526 { /* sentinel */ } 527 }; 528 MODULE_DEVICE_TABLE(of, at91_rtc_dt_ids); 529 530 static struct platform_driver at91_rtc_driver = { 531 .probe = at91_rtc_probe, 532 .remove_new = at91_rtc_remove, 533 .shutdown = at91_rtc_shutdown, 534 .driver = { 535 .name = "rtc-at91sam9", 536 .pm = &at91_rtc_pm_ops, 537 .of_match_table = at91_rtc_dt_ids, 538 }, 539 }; 540 541 module_platform_driver(at91_rtc_driver); 542 543 MODULE_AUTHOR("Michel Benoit"); 544 MODULE_DESCRIPTION("RTC driver for Atmel AT91SAM9x"); 545 MODULE_LICENSE("GPL"); 546