/* * rtc-ds1305.c -- driver for DS1305 and DS1306 SPI RTC chips * * Copyright (C) 2008 David Brownell * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * */ #include #include #include #include #include #include #include #include #include /* * Registers ... mask DS1305_WRITE into register address to write, * otherwise you're reading it. All non-bitmask values are BCD. */ #define DS1305_WRITE 0x80 /* RTC date/time ... the main special cases are that we: * - Need fancy "hours" encoding in 12hour mode * - Don't rely on the "day-of-week" field (or tm_wday) * - Are a 21st-century clock (2000 <= year < 2100) */ #define DS1305_RTC_LEN 7 /* bytes for RTC regs */ #define DS1305_SEC 0x00 /* register addresses */ #define DS1305_MIN 0x01 #define DS1305_HOUR 0x02 # define DS1305_HR_12 0x40 /* set == 12 hr mode */ # define DS1305_HR_PM 0x20 /* set == PM (12hr mode) */ #define DS1305_WDAY 0x03 #define DS1305_MDAY 0x04 #define DS1305_MON 0x05 #define DS1305_YEAR 0x06 /* The two alarms have only sec/min/hour/wday fields (ALM_LEN). * DS1305_ALM_DISABLE disables a match field (some combos are bad). * * NOTE that since we don't use WDAY, we limit ourselves to alarms * only one day into the future (vs potentially up to a week). * * NOTE ALSO that while we could generate once-a-second IRQs (UIE), we * don't currently support them. We'd either need to do it only when * no alarm is pending (not the standard model), or to use the second * alarm (implying that this is a DS1305 not DS1306, *and* that either * it's wired up a second IRQ we know, or that INTCN is set) */ #define DS1305_ALM_LEN 4 /* bytes for ALM regs */ #define DS1305_ALM_DISABLE 0x80 #define DS1305_ALM0(r) (0x07 + (r)) /* register addresses */ #define DS1305_ALM1(r) (0x0b + (r)) /* three control registers */ #define DS1305_CONTROL_LEN 3 /* bytes of control regs */ #define DS1305_CONTROL 0x0f /* register addresses */ # define DS1305_nEOSC 0x80 /* low enables oscillator */ # define DS1305_WP 0x40 /* write protect */ # define DS1305_INTCN 0x04 /* clear == only int0 used */ # define DS1306_1HZ 0x04 /* enable 1Hz output */ # define DS1305_AEI1 0x02 /* enable ALM1 IRQ */ # define DS1305_AEI0 0x01 /* enable ALM0 IRQ */ #define DS1305_STATUS 0x10 /* status has just AEIx bits, mirrored as IRQFx */ #define DS1305_TRICKLE 0x11 /* trickle bits are defined in */ /* a bunch of NVRAM */ #define DS1305_NVRAM_LEN 96 /* bytes of NVRAM */ #define DS1305_NVRAM 0x20 /* register addresses */ struct ds1305 { struct spi_device *spi; struct rtc_device *rtc; struct work_struct work; unsigned long flags; #define FLAG_EXITING 0 bool hr12; u8 ctrl[DS1305_CONTROL_LEN]; }; /*----------------------------------------------------------------------*/ /* * Utilities ... tolerate 12-hour AM/PM notation in case of non-Linux * software (like a bootloader) which may require it. */ static unsigned bcd2hour(u8 bcd) { if (bcd & DS1305_HR_12) { unsigned hour = 0; bcd &= ~DS1305_HR_12; if (bcd & DS1305_HR_PM) { hour = 12; bcd &= ~DS1305_HR_PM; } hour += bcd2bin(bcd); return hour - 1; } return bcd2bin(bcd); } static u8 hour2bcd(bool hr12, int hour) { if (hr12) { hour++; if (hour <= 12) return DS1305_HR_12 | bin2bcd(hour); hour -= 12; return DS1305_HR_12 | DS1305_HR_PM | bin2bcd(hour); } return bin2bcd(hour); } /*----------------------------------------------------------------------*/ /* * Interface to RTC framework */ static int ds1305_alarm_irq_enable(struct device *dev, unsigned int enabled) { struct ds1305 *ds1305 = dev_get_drvdata(dev); u8 buf[2]; long err = -EINVAL; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; if (enabled) { if (ds1305->ctrl[0] & DS1305_AEI0) goto done; buf[1] |= DS1305_AEI0; } else { if (!(buf[1] & DS1305_AEI0)) goto done; buf[1] &= ~DS1305_AEI0; } err = spi_write_then_read(ds1305->spi, buf, sizeof(buf), NULL, 0); if (err >= 0) ds1305->ctrl[0] = buf[1]; done: return err; } /* * Get/set of date and time is pretty normal. */ static int ds1305_get_time(struct device *dev, struct rtc_time *time) { struct ds1305 *ds1305 = dev_get_drvdata(dev); u8 addr = DS1305_SEC; u8 buf[DS1305_RTC_LEN]; int status; /* Use write-then-read to get all the date/time registers * since dma from stack is nonportable */ status = spi_write_then_read(ds1305->spi, &addr, sizeof(addr), buf, sizeof(buf)); if (status < 0) return status; dev_vdbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n", "read", buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6]); /* Decode the registers */ time->tm_sec = bcd2bin(buf[DS1305_SEC]); time->tm_min = bcd2bin(buf[DS1305_MIN]); time->tm_hour = bcd2hour(buf[DS1305_HOUR]); time->tm_wday = buf[DS1305_WDAY] - 1; time->tm_mday = bcd2bin(buf[DS1305_MDAY]); time->tm_mon = bcd2bin(buf[DS1305_MON]) - 1; time->tm_year = bcd2bin(buf[DS1305_YEAR]) + 100; dev_vdbg(dev, "%s secs=%d, mins=%d, " "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", "read", time->tm_sec, time->tm_min, time->tm_hour, time->tm_mday, time->tm_mon, time->tm_year, time->tm_wday); /* Time may not be set */ return rtc_valid_tm(time); } static int ds1305_set_time(struct device *dev, struct rtc_time *time) { struct ds1305 *ds1305 = dev_get_drvdata(dev); u8 buf[1 + DS1305_RTC_LEN]; u8 *bp = buf; dev_vdbg(dev, "%s secs=%d, mins=%d, " "hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n", "write", time->tm_sec, time->tm_min, time->tm_hour, time->tm_mday, time->tm_mon, time->tm_year, time->tm_wday); /* Write registers starting at the first time/date address. */ *bp++ = DS1305_WRITE | DS1305_SEC; *bp++ = bin2bcd(time->tm_sec); *bp++ = bin2bcd(time->tm_min); *bp++ = hour2bcd(ds1305->hr12, time->tm_hour); *bp++ = (time->tm_wday < 7) ? (time->tm_wday + 1) : 1; *bp++ = bin2bcd(time->tm_mday); *bp++ = bin2bcd(time->tm_mon + 1); *bp++ = bin2bcd(time->tm_year - 100); dev_dbg(dev, "%s: %02x %02x %02x, %02x %02x %02x %02x\n", "write", buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]); /* use write-then-read since dma from stack is nonportable */ return spi_write_then_read(ds1305->spi, buf, sizeof(buf), NULL, 0); } /* * Get/set of alarm is a bit funky: * * - First there's the inherent raciness of getting the (partitioned) * status of an alarm that could trigger while we're reading parts * of that status. * * - Second there's its limited range (we could increase it a bit by * relying on WDAY), which means it will easily roll over. * * - Third there's the choice of two alarms and alarm signals. * Here we use ALM0 and expect that nINT0 (open drain) is used; * that's the only real option for DS1306 runtime alarms, and is * natural on DS1305. * * - Fourth, there's also ALM1, and a second interrupt signal: * + On DS1305 ALM1 uses nINT1 (when INTCN=1) else nINT0; * + On DS1306 ALM1 only uses INT1 (an active high pulse) * and it won't work when VCC1 is active. * * So to be most general, we should probably set both alarms to the * same value, letting ALM1 be the wakeup event source on DS1306 * and handling several wiring options on DS1305. * * - Fifth, we support the polled mode (as well as possible; why not?) * even when no interrupt line is wired to an IRQ. */ /* * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl) */ static int ds1305_get_alarm(struct device *dev, struct rtc_wkalrm *alm) { struct ds1305 *ds1305 = dev_get_drvdata(dev); struct spi_device *spi = ds1305->spi; u8 addr; int status; u8 buf[DS1305_ALM_LEN]; /* Refresh control register cache BEFORE reading ALM0 registers, * since reading alarm registers acks any pending IRQ. That * makes returning "pending" status a bit of a lie, but that bit * of EFI status is at best fragile anyway (given IRQ handlers). */ addr = DS1305_CONTROL; status = spi_write_then_read(spi, &addr, sizeof(addr), ds1305->ctrl, sizeof(ds1305->ctrl)); if (status < 0) return status; alm->enabled = !!(ds1305->ctrl[0] & DS1305_AEI0); alm->pending = !!(ds1305->ctrl[1] & DS1305_AEI0); /* get and check ALM0 registers */ addr = DS1305_ALM0(DS1305_SEC); status = spi_write_then_read(spi, &addr, sizeof(addr), buf, sizeof(buf)); if (status < 0) return status; dev_vdbg(dev, "%s: %02x %02x %02x %02x\n", "alm0 read", buf[DS1305_SEC], buf[DS1305_MIN], buf[DS1305_HOUR], buf[DS1305_WDAY]); if ((DS1305_ALM_DISABLE & buf[DS1305_SEC]) || (DS1305_ALM_DISABLE & buf[DS1305_MIN]) || (DS1305_ALM_DISABLE & buf[DS1305_HOUR])) return -EIO; /* Stuff these values into alm->time and let RTC framework code * fill in the rest ... and also handle rollover to tomorrow when * that's needed. */ alm->time.tm_sec = bcd2bin(buf[DS1305_SEC]); alm->time.tm_min = bcd2bin(buf[DS1305_MIN]); alm->time.tm_hour = bcd2hour(buf[DS1305_HOUR]); alm->time.tm_mday = -1; alm->time.tm_mon = -1; alm->time.tm_year = -1; /* next three fields are unused by Linux */ alm->time.tm_wday = -1; alm->time.tm_mday = -1; alm->time.tm_isdst = -1; return 0; } /* * Context: caller holds rtc->ops_lock (to protect ds1305->ctrl) */ static int ds1305_set_alarm(struct device *dev, struct rtc_wkalrm *alm) { struct ds1305 *ds1305 = dev_get_drvdata(dev); struct spi_device *spi = ds1305->spi; unsigned long now, later; struct rtc_time tm; int status; u8 buf[1 + DS1305_ALM_LEN]; /* convert desired alarm to time_t */ status = rtc_tm_to_time(&alm->time, &later); if (status < 0) return status; /* Read current time as time_t */ status = ds1305_get_time(dev, &tm); if (status < 0) return status; status = rtc_tm_to_time(&tm, &now); if (status < 0) return status; /* make sure alarm fires within the next 24 hours */ if (later <= now) return -EINVAL; if ((later - now) > 24 * 60 * 60) return -EDOM; /* disable alarm if needed */ if (ds1305->ctrl[0] & DS1305_AEI0) { ds1305->ctrl[0] &= ~DS1305_AEI0; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0); if (status < 0) return status; } /* write alarm */ buf[0] = DS1305_WRITE | DS1305_ALM0(DS1305_SEC); buf[1 + DS1305_SEC] = bin2bcd(alm->time.tm_sec); buf[1 + DS1305_MIN] = bin2bcd(alm->time.tm_min); buf[1 + DS1305_HOUR] = hour2bcd(ds1305->hr12, alm->time.tm_hour); buf[1 + DS1305_WDAY] = DS1305_ALM_DISABLE; dev_dbg(dev, "%s: %02x %02x %02x %02x\n", "alm0 write", buf[1 + DS1305_SEC], buf[1 + DS1305_MIN], buf[1 + DS1305_HOUR], buf[1 + DS1305_WDAY]); status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0); if (status < 0) return status; /* enable alarm if requested */ if (alm->enabled) { ds1305->ctrl[0] |= DS1305_AEI0; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; status = spi_write_then_read(ds1305->spi, buf, 2, NULL, 0); } return status; } #ifdef CONFIG_PROC_FS static int ds1305_proc(struct device *dev, struct seq_file *seq) { struct ds1305 *ds1305 = dev_get_drvdata(dev); char *diodes = "no"; char *resistors = ""; /* ctrl[2] is treated as read-only; no locking needed */ if ((ds1305->ctrl[2] & 0xf0) == DS1305_TRICKLE_MAGIC) { switch (ds1305->ctrl[2] & 0x0c) { case DS1305_TRICKLE_DS2: diodes = "2 diodes, "; break; case DS1305_TRICKLE_DS1: diodes = "1 diode, "; break; default: goto done; } switch (ds1305->ctrl[2] & 0x03) { case DS1305_TRICKLE_2K: resistors = "2k Ohm"; break; case DS1305_TRICKLE_4K: resistors = "4k Ohm"; break; case DS1305_TRICKLE_8K: resistors = "8k Ohm"; break; default: diodes = "no"; break; } } done: return seq_printf(seq, "trickle_charge\t: %s%s\n", diodes, resistors); } #else #define ds1305_proc NULL #endif static const struct rtc_class_ops ds1305_ops = { .read_time = ds1305_get_time, .set_time = ds1305_set_time, .read_alarm = ds1305_get_alarm, .set_alarm = ds1305_set_alarm, .proc = ds1305_proc, .alarm_irq_enable = ds1305_alarm_irq_enable, }; static void ds1305_work(struct work_struct *work) { struct ds1305 *ds1305 = container_of(work, struct ds1305, work); struct mutex *lock = &ds1305->rtc->ops_lock; struct spi_device *spi = ds1305->spi; u8 buf[3]; int status; /* lock to protect ds1305->ctrl */ mutex_lock(lock); /* Disable the IRQ, and clear its status ... for now, we "know" * that if more than one alarm is active, they're in sync. * Note that reading ALM data registers also clears IRQ status. */ ds1305->ctrl[0] &= ~(DS1305_AEI1 | DS1305_AEI0); ds1305->ctrl[1] = 0; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; buf[2] = 0; status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0); if (status < 0) dev_dbg(&spi->dev, "clear irq --> %d\n", status); mutex_unlock(lock); if (!test_bit(FLAG_EXITING, &ds1305->flags)) enable_irq(spi->irq); rtc_update_irq(ds1305->rtc, 1, RTC_AF | RTC_IRQF); } /* * This "real" IRQ handler hands off to a workqueue mostly to allow * mutex locking for ds1305->ctrl ... unlike I2C, we could issue async * I/O requests in IRQ context (to clear the IRQ status). */ static irqreturn_t ds1305_irq(int irq, void *p) { struct ds1305 *ds1305 = p; disable_irq(irq); schedule_work(&ds1305->work); return IRQ_HANDLED; } /*----------------------------------------------------------------------*/ /* * Interface for NVRAM */ static void msg_init(struct spi_message *m, struct spi_transfer *x, u8 *addr, size_t count, char *tx, char *rx) { spi_message_init(m); memset(x, 0, 2 * sizeof(*x)); x->tx_buf = addr; x->len = 1; spi_message_add_tail(x, m); x++; x->tx_buf = tx; x->rx_buf = rx; x->len = count; spi_message_add_tail(x, m); } static ssize_t ds1305_nvram_read(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) { struct spi_device *spi; u8 addr; struct spi_message m; struct spi_transfer x[2]; int status; spi = container_of(kobj, struct spi_device, dev.kobj); if (unlikely(off >= DS1305_NVRAM_LEN)) return 0; if (count >= DS1305_NVRAM_LEN) count = DS1305_NVRAM_LEN; if ((off + count) > DS1305_NVRAM_LEN) count = DS1305_NVRAM_LEN - off; if (unlikely(!count)) return count; addr = DS1305_NVRAM + off; msg_init(&m, x, &addr, count, NULL, buf); status = spi_sync(spi, &m); if (status < 0) dev_err(&spi->dev, "nvram %s error %d\n", "read", status); return (status < 0) ? status : count; } static ssize_t ds1305_nvram_write(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) { struct spi_device *spi; u8 addr; struct spi_message m; struct spi_transfer x[2]; int status; spi = container_of(kobj, struct spi_device, dev.kobj); if (unlikely(off >= DS1305_NVRAM_LEN)) return -EFBIG; if (count >= DS1305_NVRAM_LEN) count = DS1305_NVRAM_LEN; if ((off + count) > DS1305_NVRAM_LEN) count = DS1305_NVRAM_LEN - off; if (unlikely(!count)) return count; addr = (DS1305_WRITE | DS1305_NVRAM) + off; msg_init(&m, x, &addr, count, buf, NULL); status = spi_sync(spi, &m); if (status < 0) dev_err(&spi->dev, "nvram %s error %d\n", "write", status); return (status < 0) ? status : count; } static struct bin_attribute nvram = { .attr.name = "nvram", .attr.mode = S_IRUGO | S_IWUSR, .read = ds1305_nvram_read, .write = ds1305_nvram_write, .size = DS1305_NVRAM_LEN, }; /*----------------------------------------------------------------------*/ /* * Interface to SPI stack */ static int ds1305_probe(struct spi_device *spi) { struct ds1305 *ds1305; int status; u8 addr, value; struct ds1305_platform_data *pdata = dev_get_platdata(&spi->dev); bool write_ctrl = false; /* Sanity check board setup data. This may be hooked up * in 3wire mode, but we don't care. Note that unless * there's an inverter in place, this needs SPI_CS_HIGH! */ if ((spi->bits_per_word && spi->bits_per_word != 8) || (spi->max_speed_hz > 2000000) || !(spi->mode & SPI_CPHA)) return -EINVAL; /* set up driver data */ ds1305 = devm_kzalloc(&spi->dev, sizeof(*ds1305), GFP_KERNEL); if (!ds1305) return -ENOMEM; ds1305->spi = spi; spi_set_drvdata(spi, ds1305); /* read and cache control registers */ addr = DS1305_CONTROL; status = spi_write_then_read(spi, &addr, sizeof(addr), ds1305->ctrl, sizeof(ds1305->ctrl)); if (status < 0) { dev_dbg(&spi->dev, "can't %s, %d\n", "read", status); return status; } dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "read", ds1305->ctrl); /* Sanity check register values ... partially compensating for the * fact that SPI has no device handshake. A pullup on MISO would * make these tests fail; but not all systems will have one. If * some register is neither 0x00 nor 0xff, a chip is likely there. */ if ((ds1305->ctrl[0] & 0x38) != 0 || (ds1305->ctrl[1] & 0xfc) != 0) { dev_dbg(&spi->dev, "RTC chip is not present\n"); return -ENODEV; } if (ds1305->ctrl[2] == 0) dev_dbg(&spi->dev, "chip may not be present\n"); /* enable writes if needed ... if we were paranoid it would * make sense to enable them only when absolutely necessary. */ if (ds1305->ctrl[0] & DS1305_WP) { u8 buf[2]; ds1305->ctrl[0] &= ~DS1305_WP; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0); dev_dbg(&spi->dev, "clear WP --> %d\n", status); if (status < 0) return status; } /* on DS1305, maybe start oscillator; like most low power * oscillators, it may take a second to stabilize */ if (ds1305->ctrl[0] & DS1305_nEOSC) { ds1305->ctrl[0] &= ~DS1305_nEOSC; write_ctrl = true; dev_warn(&spi->dev, "SET TIME!\n"); } /* ack any pending IRQs */ if (ds1305->ctrl[1]) { ds1305->ctrl[1] = 0; write_ctrl = true; } /* this may need one-time (re)init */ if (pdata) { /* maybe enable trickle charge */ if (((ds1305->ctrl[2] & 0xf0) != DS1305_TRICKLE_MAGIC)) { ds1305->ctrl[2] = DS1305_TRICKLE_MAGIC | pdata->trickle; write_ctrl = true; } /* on DS1306, configure 1 Hz signal */ if (pdata->is_ds1306) { if (pdata->en_1hz) { if (!(ds1305->ctrl[0] & DS1306_1HZ)) { ds1305->ctrl[0] |= DS1306_1HZ; write_ctrl = true; } } else { if (ds1305->ctrl[0] & DS1306_1HZ) { ds1305->ctrl[0] &= ~DS1306_1HZ; write_ctrl = true; } } } } if (write_ctrl) { u8 buf[4]; buf[0] = DS1305_WRITE | DS1305_CONTROL; buf[1] = ds1305->ctrl[0]; buf[2] = ds1305->ctrl[1]; buf[3] = ds1305->ctrl[2]; status = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0); if (status < 0) { dev_dbg(&spi->dev, "can't %s, %d\n", "write", status); return status; } dev_dbg(&spi->dev, "ctrl %s: %3ph\n", "write", ds1305->ctrl); } /* see if non-Linux software set up AM/PM mode */ addr = DS1305_HOUR; status = spi_write_then_read(spi, &addr, sizeof(addr), &value, sizeof(value)); if (status < 0) { dev_dbg(&spi->dev, "read HOUR --> %d\n", status); return status; } ds1305->hr12 = (DS1305_HR_12 & value) != 0; if (ds1305->hr12) dev_dbg(&spi->dev, "AM/PM\n"); /* register RTC ... from here on, ds1305->ctrl needs locking */ ds1305->rtc = devm_rtc_device_register(&spi->dev, "ds1305", &ds1305_ops, THIS_MODULE); if (IS_ERR(ds1305->rtc)) { status = PTR_ERR(ds1305->rtc); dev_dbg(&spi->dev, "register rtc --> %d\n", status); return status; } /* Maybe set up alarm IRQ; be ready to handle it triggering right * away. NOTE that we don't share this. The signal is active low, * and we can't ack it before a SPI message delay. We temporarily * disable the IRQ until it's acked, which lets us work with more * IRQ trigger modes (not all IRQ controllers can do falling edge). */ if (spi->irq) { INIT_WORK(&ds1305->work, ds1305_work); status = devm_request_irq(&spi->dev, spi->irq, ds1305_irq, 0, dev_name(&ds1305->rtc->dev), ds1305); if (status < 0) { dev_err(&spi->dev, "request_irq %d --> %d\n", spi->irq, status); } else { device_set_wakeup_capable(&spi->dev, 1); } } /* export NVRAM */ status = sysfs_create_bin_file(&spi->dev.kobj, &nvram); if (status < 0) { dev_err(&spi->dev, "register nvram --> %d\n", status); } return 0; } static int ds1305_remove(struct spi_device *spi) { struct ds1305 *ds1305 = spi_get_drvdata(spi); sysfs_remove_bin_file(&spi->dev.kobj, &nvram); /* carefully shut down irq and workqueue, if present */ if (spi->irq) { set_bit(FLAG_EXITING, &ds1305->flags); devm_free_irq(&spi->dev, spi->irq, ds1305); cancel_work_sync(&ds1305->work); } return 0; } static struct spi_driver ds1305_driver = { .driver.name = "rtc-ds1305", .driver.owner = THIS_MODULE, .probe = ds1305_probe, .remove = ds1305_remove, /* REVISIT add suspend/resume */ }; module_spi_driver(ds1305_driver); MODULE_DESCRIPTION("RTC driver for DS1305 and DS1306 chips"); MODULE_LICENSE("GPL"); MODULE_ALIAS("spi:rtc-ds1305");