1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * An RTC driver for the NVIDIA Tegra 200 series internal RTC. 4 * 5 * Copyright (c) 2010-2019, NVIDIA Corporation. 6 */ 7 8 #include <linux/clk.h> 9 #include <linux/delay.h> 10 #include <linux/init.h> 11 #include <linux/io.h> 12 #include <linux/irq.h> 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/mod_devicetable.h> 16 #include <linux/platform_device.h> 17 #include <linux/pm.h> 18 #include <linux/rtc.h> 19 #include <linux/slab.h> 20 21 /* Set to 1 = busy every eight 32 kHz clocks during copy of sec+msec to AHB. */ 22 #define TEGRA_RTC_REG_BUSY 0x004 23 #define TEGRA_RTC_REG_SECONDS 0x008 24 /* When msec is read, the seconds are buffered into shadow seconds. */ 25 #define TEGRA_RTC_REG_SHADOW_SECONDS 0x00c 26 #define TEGRA_RTC_REG_MILLI_SECONDS 0x010 27 #define TEGRA_RTC_REG_SECONDS_ALARM0 0x014 28 #define TEGRA_RTC_REG_SECONDS_ALARM1 0x018 29 #define TEGRA_RTC_REG_MILLI_SECONDS_ALARM0 0x01c 30 #define TEGRA_RTC_REG_INTR_MASK 0x028 31 /* write 1 bits to clear status bits */ 32 #define TEGRA_RTC_REG_INTR_STATUS 0x02c 33 34 /* bits in INTR_MASK */ 35 #define TEGRA_RTC_INTR_MASK_MSEC_CDN_ALARM (1<<4) 36 #define TEGRA_RTC_INTR_MASK_SEC_CDN_ALARM (1<<3) 37 #define TEGRA_RTC_INTR_MASK_MSEC_ALARM (1<<2) 38 #define TEGRA_RTC_INTR_MASK_SEC_ALARM1 (1<<1) 39 #define TEGRA_RTC_INTR_MASK_SEC_ALARM0 (1<<0) 40 41 /* bits in INTR_STATUS */ 42 #define TEGRA_RTC_INTR_STATUS_MSEC_CDN_ALARM (1<<4) 43 #define TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM (1<<3) 44 #define TEGRA_RTC_INTR_STATUS_MSEC_ALARM (1<<2) 45 #define TEGRA_RTC_INTR_STATUS_SEC_ALARM1 (1<<1) 46 #define TEGRA_RTC_INTR_STATUS_SEC_ALARM0 (1<<0) 47 48 struct tegra_rtc_info { 49 struct platform_device *pdev; 50 struct rtc_device *rtc; 51 void __iomem *base; /* NULL if not initialized */ 52 struct clk *clk; 53 int irq; /* alarm and periodic IRQ */ 54 spinlock_t lock; 55 }; 56 57 /* 58 * RTC hardware is busy when it is updating its values over AHB once every 59 * eight 32 kHz clocks (~250 us). Outside of these updates the CPU is free to 60 * write. CPU is always free to read. 61 */ 62 static inline u32 tegra_rtc_check_busy(struct tegra_rtc_info *info) 63 { 64 return readl(info->base + TEGRA_RTC_REG_BUSY) & 1; 65 } 66 67 /* 68 * Wait for hardware to be ready for writing. This function tries to maximize 69 * the amount of time before the next update. It does this by waiting for the 70 * RTC to become busy with its periodic update, then returning once the RTC 71 * first becomes not busy. 72 * 73 * This periodic update (where the seconds and milliseconds are copied to the 74 * AHB side) occurs every eight 32 kHz clocks (~250 us). The behavior of this 75 * function allows us to make some assumptions without introducing a race, 76 * because 250 us is plenty of time to read/write a value. 77 */ 78 static int tegra_rtc_wait_while_busy(struct device *dev) 79 { 80 struct tegra_rtc_info *info = dev_get_drvdata(dev); 81 int retries = 500; /* ~490 us is the worst case, ~250 us is best */ 82 83 /* 84 * First wait for the RTC to become busy. This is when it posts its 85 * updated seconds+msec registers to AHB side. 86 */ 87 while (tegra_rtc_check_busy(info)) { 88 if (!retries--) 89 goto retry_failed; 90 91 udelay(1); 92 } 93 94 /* now we have about 250 us to manipulate registers */ 95 return 0; 96 97 retry_failed: 98 dev_err(dev, "write failed: retry count exceeded\n"); 99 return -ETIMEDOUT; 100 } 101 102 static int tegra_rtc_read_time(struct device *dev, struct rtc_time *tm) 103 { 104 struct tegra_rtc_info *info = dev_get_drvdata(dev); 105 unsigned long flags; 106 u32 sec; 107 108 /* 109 * RTC hardware copies seconds to shadow seconds when a read of 110 * milliseconds occurs. use a lock to keep other threads out. 111 */ 112 spin_lock_irqsave(&info->lock, flags); 113 114 readl(info->base + TEGRA_RTC_REG_MILLI_SECONDS); 115 sec = readl(info->base + TEGRA_RTC_REG_SHADOW_SECONDS); 116 117 spin_unlock_irqrestore(&info->lock, flags); 118 119 rtc_time64_to_tm(sec, tm); 120 121 dev_vdbg(dev, "time read as %u, %ptR\n", sec, tm); 122 123 return 0; 124 } 125 126 static int tegra_rtc_set_time(struct device *dev, struct rtc_time *tm) 127 { 128 struct tegra_rtc_info *info = dev_get_drvdata(dev); 129 u32 sec; 130 int ret; 131 132 /* convert tm to seconds */ 133 sec = rtc_tm_to_time64(tm); 134 135 dev_vdbg(dev, "time set to %u, %ptR\n", sec, tm); 136 137 /* seconds only written if wait succeeded */ 138 ret = tegra_rtc_wait_while_busy(dev); 139 if (!ret) 140 writel(sec, info->base + TEGRA_RTC_REG_SECONDS); 141 142 dev_vdbg(dev, "time read back as %d\n", 143 readl(info->base + TEGRA_RTC_REG_SECONDS)); 144 145 return ret; 146 } 147 148 static int tegra_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm) 149 { 150 struct tegra_rtc_info *info = dev_get_drvdata(dev); 151 u32 sec, value; 152 153 sec = readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0); 154 155 if (sec == 0) { 156 /* alarm is disabled */ 157 alarm->enabled = 0; 158 } else { 159 /* alarm is enabled */ 160 alarm->enabled = 1; 161 rtc_time64_to_tm(sec, &alarm->time); 162 } 163 164 value = readl(info->base + TEGRA_RTC_REG_INTR_STATUS); 165 alarm->pending = (value & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) != 0; 166 167 return 0; 168 } 169 170 static int tegra_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled) 171 { 172 struct tegra_rtc_info *info = dev_get_drvdata(dev); 173 unsigned long flags; 174 u32 status; 175 176 tegra_rtc_wait_while_busy(dev); 177 spin_lock_irqsave(&info->lock, flags); 178 179 /* read the original value, and OR in the flag */ 180 status = readl(info->base + TEGRA_RTC_REG_INTR_MASK); 181 if (enabled) 182 status |= TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* set it */ 183 else 184 status &= ~TEGRA_RTC_INTR_MASK_SEC_ALARM0; /* clear it */ 185 186 writel(status, info->base + TEGRA_RTC_REG_INTR_MASK); 187 188 spin_unlock_irqrestore(&info->lock, flags); 189 190 return 0; 191 } 192 193 static int tegra_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm) 194 { 195 struct tegra_rtc_info *info = dev_get_drvdata(dev); 196 u32 sec; 197 198 if (alarm->enabled) 199 sec = rtc_tm_to_time64(&alarm->time); 200 else 201 sec = 0; 202 203 tegra_rtc_wait_while_busy(dev); 204 writel(sec, info->base + TEGRA_RTC_REG_SECONDS_ALARM0); 205 dev_vdbg(dev, "alarm read back as %d\n", 206 readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0)); 207 208 /* if successfully written and alarm is enabled ... */ 209 if (sec) { 210 tegra_rtc_alarm_irq_enable(dev, 1); 211 dev_vdbg(dev, "alarm set as %u, %ptR\n", sec, &alarm->time); 212 } else { 213 /* disable alarm if 0 or write error */ 214 dev_vdbg(dev, "alarm disabled\n"); 215 tegra_rtc_alarm_irq_enable(dev, 0); 216 } 217 218 return 0; 219 } 220 221 static int tegra_rtc_proc(struct device *dev, struct seq_file *seq) 222 { 223 if (!dev || !dev->driver) 224 return 0; 225 226 seq_printf(seq, "name\t\t: %s\n", dev_name(dev)); 227 228 return 0; 229 } 230 231 static irqreturn_t tegra_rtc_irq_handler(int irq, void *data) 232 { 233 struct device *dev = data; 234 struct tegra_rtc_info *info = dev_get_drvdata(dev); 235 unsigned long events = 0, flags; 236 u32 status; 237 238 status = readl(info->base + TEGRA_RTC_REG_INTR_STATUS); 239 if (status) { 240 /* clear the interrupt masks and status on any IRQ */ 241 tegra_rtc_wait_while_busy(dev); 242 243 spin_lock_irqsave(&info->lock, flags); 244 writel(0, info->base + TEGRA_RTC_REG_INTR_MASK); 245 writel(status, info->base + TEGRA_RTC_REG_INTR_STATUS); 246 spin_unlock_irqrestore(&info->lock, flags); 247 } 248 249 /* check if alarm */ 250 if (status & TEGRA_RTC_INTR_STATUS_SEC_ALARM0) 251 events |= RTC_IRQF | RTC_AF; 252 253 /* check if periodic */ 254 if (status & TEGRA_RTC_INTR_STATUS_SEC_CDN_ALARM) 255 events |= RTC_IRQF | RTC_PF; 256 257 rtc_update_irq(info->rtc, 1, events); 258 259 return IRQ_HANDLED; 260 } 261 262 static const struct rtc_class_ops tegra_rtc_ops = { 263 .read_time = tegra_rtc_read_time, 264 .set_time = tegra_rtc_set_time, 265 .read_alarm = tegra_rtc_read_alarm, 266 .set_alarm = tegra_rtc_set_alarm, 267 .proc = tegra_rtc_proc, 268 .alarm_irq_enable = tegra_rtc_alarm_irq_enable, 269 }; 270 271 static const struct of_device_id tegra_rtc_dt_match[] = { 272 { .compatible = "nvidia,tegra20-rtc", }, 273 {} 274 }; 275 MODULE_DEVICE_TABLE(of, tegra_rtc_dt_match); 276 277 static int tegra_rtc_probe(struct platform_device *pdev) 278 { 279 struct tegra_rtc_info *info; 280 int ret; 281 282 info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL); 283 if (!info) 284 return -ENOMEM; 285 286 info->base = devm_platform_ioremap_resource(pdev, 0); 287 if (IS_ERR(info->base)) 288 return PTR_ERR(info->base); 289 290 ret = platform_get_irq(pdev, 0); 291 if (ret <= 0) 292 return ret; 293 294 info->irq = ret; 295 296 info->rtc = devm_rtc_allocate_device(&pdev->dev); 297 if (IS_ERR(info->rtc)) 298 return PTR_ERR(info->rtc); 299 300 info->rtc->ops = &tegra_rtc_ops; 301 info->rtc->range_max = U32_MAX; 302 303 info->clk = devm_clk_get(&pdev->dev, NULL); 304 if (IS_ERR(info->clk)) 305 return PTR_ERR(info->clk); 306 307 ret = clk_prepare_enable(info->clk); 308 if (ret < 0) 309 return ret; 310 311 /* set context info */ 312 info->pdev = pdev; 313 spin_lock_init(&info->lock); 314 315 platform_set_drvdata(pdev, info); 316 317 /* clear out the hardware */ 318 writel(0, info->base + TEGRA_RTC_REG_SECONDS_ALARM0); 319 writel(0xffffffff, info->base + TEGRA_RTC_REG_INTR_STATUS); 320 writel(0, info->base + TEGRA_RTC_REG_INTR_MASK); 321 322 device_init_wakeup(&pdev->dev, 1); 323 324 ret = devm_request_irq(&pdev->dev, info->irq, tegra_rtc_irq_handler, 325 IRQF_TRIGGER_HIGH, dev_name(&pdev->dev), 326 &pdev->dev); 327 if (ret) { 328 dev_err(&pdev->dev, "failed to request interrupt: %d\n", ret); 329 goto disable_clk; 330 } 331 332 ret = devm_rtc_register_device(info->rtc); 333 if (ret) 334 goto disable_clk; 335 336 dev_notice(&pdev->dev, "Tegra internal Real Time Clock\n"); 337 338 return 0; 339 340 disable_clk: 341 clk_disable_unprepare(info->clk); 342 return ret; 343 } 344 345 static int tegra_rtc_remove(struct platform_device *pdev) 346 { 347 struct tegra_rtc_info *info = platform_get_drvdata(pdev); 348 349 clk_disable_unprepare(info->clk); 350 351 return 0; 352 } 353 354 #ifdef CONFIG_PM_SLEEP 355 static int tegra_rtc_suspend(struct device *dev) 356 { 357 struct tegra_rtc_info *info = dev_get_drvdata(dev); 358 359 tegra_rtc_wait_while_busy(dev); 360 361 /* only use ALARM0 as a wake source */ 362 writel(0xffffffff, info->base + TEGRA_RTC_REG_INTR_STATUS); 363 writel(TEGRA_RTC_INTR_STATUS_SEC_ALARM0, 364 info->base + TEGRA_RTC_REG_INTR_MASK); 365 366 dev_vdbg(dev, "alarm sec = %d\n", 367 readl(info->base + TEGRA_RTC_REG_SECONDS_ALARM0)); 368 369 dev_vdbg(dev, "Suspend (device_may_wakeup=%d) IRQ:%d\n", 370 device_may_wakeup(dev), info->irq); 371 372 /* leave the alarms on as a wake source */ 373 if (device_may_wakeup(dev)) 374 enable_irq_wake(info->irq); 375 376 return 0; 377 } 378 379 static int tegra_rtc_resume(struct device *dev) 380 { 381 struct tegra_rtc_info *info = dev_get_drvdata(dev); 382 383 dev_vdbg(dev, "Resume (device_may_wakeup=%d)\n", 384 device_may_wakeup(dev)); 385 386 /* alarms were left on as a wake source, turn them off */ 387 if (device_may_wakeup(dev)) 388 disable_irq_wake(info->irq); 389 390 return 0; 391 } 392 #endif 393 394 static SIMPLE_DEV_PM_OPS(tegra_rtc_pm_ops, tegra_rtc_suspend, tegra_rtc_resume); 395 396 static void tegra_rtc_shutdown(struct platform_device *pdev) 397 { 398 dev_vdbg(&pdev->dev, "disabling interrupts\n"); 399 tegra_rtc_alarm_irq_enable(&pdev->dev, 0); 400 } 401 402 static struct platform_driver tegra_rtc_driver = { 403 .probe = tegra_rtc_probe, 404 .remove = tegra_rtc_remove, 405 .shutdown = tegra_rtc_shutdown, 406 .driver = { 407 .name = "tegra_rtc", 408 .of_match_table = tegra_rtc_dt_match, 409 .pm = &tegra_rtc_pm_ops, 410 }, 411 }; 412 module_platform_driver(tegra_rtc_driver); 413 414 MODULE_AUTHOR("Jon Mayo <jmayo@nvidia.com>"); 415 MODULE_DESCRIPTION("driver for Tegra internal RTC"); 416 MODULE_LICENSE("GPL"); 417