i'm not looking to submit this as that'll be done with the rest of the Blackfin stuff, i'm just looking for feedback from some bored people who know the RTC framework :) the attached driver implements full functionality for the Blackfin on-chip RTC using the new RTC framework ... anyone mind giving it a quick look to see if there's any obvious (or not obvious) errors ? thanks ! btw, the new RTC framework is pretty neat, kudos to all -mike
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/* * Blackfin On-Chip Real Time Clock Driver * Supports BF531/BF532/BF533/BF534/BF536/BF537 * * Copyright 2004-2007 Analog Devices Inc. * * Enter bugs at http://blackfin.uclinux.org/ * * Licensed under the GPL-2 or later. */ /* The biggest issue we deal with in this driver is that register writes are * synced to the RTC frequency of 1Hz. So if you write to a register and * attempt to write again before the first write has completed, the new write * is simply discarded. This can easily be troublesome if userspace disables * one event (say periodic) and then right after enables an event (say alarm). * Since all events are maintained in the same interrupt mask register, if * we wrote to it to disable the first event and then wrote to it again to * enable the second event, that second event would not be enabled as the * write would be discarded and things quickly fall apart. * * To keep this delay from significantly degrading performance (we, in theory, * would have to sleep for up to 1 second everytime we wanted to write a * register), we only check the write pending status before we start to issue * a new write. We bank on the idea that it doesnt matter when the sync * happens so long as we don't attempt another write before it does. The only * time userspace would take this penalty is when they try and do multiple * operations right after another ... but in this case, they need to take the * sync penalty, so we should be OK. * * Also note that the RTC_ISTAT register does not suffer this penalty; its * writes to clear status registers complete immediately. */ #include <linux/module.h> #include <linux/kernel.h> #include <linux/bcd.h> #include <linux/rtc.h> #include <linux/init.h> #include <linux/platform_device.h> #include <linux/seq_file.h> #include <linux/interrupt.h> #include <linux/spinlock.h> #include <linux/delay.h> #include <asm/blackfin.h> #define stamp(fmt, args...) pr_debug("%s:%i: " fmt "\n", __FUNCTION__, __LINE__, ## args) #define stampit() stamp("here i am") struct bfin_rtc { struct rtc_device *rtc_dev; struct rtc_time rtc_alarm; spinlock_t lock; }; /* Bit values for the ISTAT / ICTL registers */ #define RTC_ISTAT_WRITE_COMPLETE 0x8000 #define RTC_ISTAT_WRITE_PENDING 0x4000 #define RTC_ISTAT_ALARM_DAY 0x0040 #define RTC_ISTAT_24HR 0x0020 #define RTC_ISTAT_HOUR 0x0010 #define RTC_ISTAT_MIN 0x0008 #define RTC_ISTAT_SEC 0x0004 #define RTC_ISTAT_ALARM 0x0002 #define RTC_ISTAT_STOPWATCH 0x0001 /* Shift values for RTC_STAT register */ #define DAY_BITS_OFF 17 #define HOUR_BITS_OFF 12 #define MIN_BITS_OFF 6 #define SEC_BITS_OFF 0 /* Some helper functions to convert between the common RTC notion of time * and the internal Blackfin notion that is stored in 32bits. */ static inline u32 rtc_time_to_bfin(unsigned long now) { u32 sec = (now % 60); u32 min = (now % (60 * 60)) / 60; u32 hour = (now % (60 * 60 * 24)) / (60 * 60); u32 days = (now / (60 * 60 * 24)); return (sec << SEC_BITS_OFF) + (min << MIN_BITS_OFF) + (hour << HOUR_BITS_OFF) + (days << DAY_BITS_OFF); } static inline unsigned long rtc_bfin_to_time(u32 rtc_bfin) { return (((rtc_bfin >> SEC_BITS_OFF) & 0x003F)) + (((rtc_bfin >> MIN_BITS_OFF) & 0x003F) * 60) + (((rtc_bfin >> HOUR_BITS_OFF) & 0x001F) * 60 * 60) + (((rtc_bfin >> DAY_BITS_OFF) & 0x7FFF) * 60 * 60 * 24); } static inline void rtc_bfin_to_tm(u32 rtc_bfin, struct rtc_time *tm) { rtc_time_to_tm(rtc_bfin_to_time(rtc_bfin), tm); } /* Wait for the previous write to a RTC register to complete. * Unfortunately, we can't sleep here as that introduces a race condition when * turning on interrupt events. Consider this: * - process sets alarm * - process enables alarm * - process sleeps while waiting for rtc write to sync * - interrupt fires while process is sleeping * - interrupt acks the event by writing to ISTAT * - interrupt sets the WRITE PENDING bit * - interrupt handler finishes * - process wakes up, sees WRITE PENDING bit set, goes to sleep * - interrupt fires while process is sleeping * If anyone can point out the obvious solution here, i'm listening :). This * shouldn't be an issue on an SMP or preempt system as this function should * only be called with the rtc lock held. */ static void rtc_bfin_sync_pending(void) { stampit(); while (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_COMPLETE)) { if (!(bfin_read_RTC_ISTAT() & RTC_ISTAT_WRITE_PENDING)) break; } bfin_write_RTC_ISTAT(RTC_ISTAT_WRITE_COMPLETE); } static void rtc_bfin_reset(struct bfin_rtc *rtc) { /* Initialize the RTC. Enable pre-scaler to scale RTC clock * to 1Hz and clear interrupt/status registers. */ spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_PREN(0x1); bfin_write_RTC_ICTL(0); bfin_write_RTC_SWCNT(0); bfin_write_RTC_ALARM(0); bfin_write_RTC_ISTAT(0xFFFF); spin_unlock_irq(&rtc->lock); } static irqreturn_t bfin_rtc_interrupt(int irq, void *dev_id) { struct platform_device *pdev = to_platform_device(dev_id); struct bfin_rtc *rtc = platform_get_drvdata(pdev); unsigned long events = 0; u16 rtc_istat; stampit(); spin_lock_irq(&rtc->lock); rtc_istat = bfin_read_RTC_ISTAT(); if (rtc_istat & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)) { bfin_write_RTC_ISTAT(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY); events |= RTC_AF | RTC_IRQF; } if (rtc_istat & RTC_ISTAT_STOPWATCH) { bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH); events |= RTC_PF | RTC_IRQF; bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq); } if (rtc_istat & RTC_ISTAT_SEC) { bfin_write_RTC_ISTAT(RTC_ISTAT_SEC); events |= RTC_UF | RTC_IRQF; } rtc_update_irq(&rtc->rtc_dev->class_dev, 1, events); spin_unlock_irq(&rtc->lock); return IRQ_HANDLED; } static int bfin_rtc_open(struct device *dev) { struct bfin_rtc *rtc = dev_get_drvdata(dev); int ret; stampit(); ret = request_irq(IRQ_RTC, bfin_rtc_interrupt, IRQF_DISABLED, "rtc-bfin", dev); if (unlikely(ret)) { dev_err(dev, "request RTC IRQ failed with %d\n", ret); return ret; } rtc_bfin_reset(rtc); return ret; } static void bfin_rtc_release(struct device *dev) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); rtc_bfin_reset(rtc); free_irq(IRQ_RTC, dev); } static int bfin_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); switch (cmd) { case RTC_PIE_ON: stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_ISTAT(RTC_ISTAT_STOPWATCH); bfin_write_RTC_SWCNT(rtc->rtc_dev->irq_freq); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_STOPWATCH); spin_unlock_irq(&rtc->lock); return 0; case RTC_PIE_OFF: stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_SWCNT(0); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_STOPWATCH); spin_unlock_irq(&rtc->lock); return 0; case RTC_UIE_ON: stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_ISTAT(RTC_ISTAT_SEC); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | RTC_ISTAT_SEC); spin_unlock_irq(&rtc->lock); return 0; case RTC_UIE_OFF: stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~RTC_ISTAT_SEC); spin_unlock_irq(&rtc->lock); return 0; case RTC_AIE_ON: { unsigned long rtc_alarm; u16 which_alarm; int ret = 0; stampit(); spin_lock_irq(&rtc->lock); if (rtc->rtc_alarm.tm_yday == -1) { struct rtc_time now; rtc_bfin_to_tm(bfin_read_RTC_STAT(), &now); now.tm_sec = rtc->rtc_alarm.tm_sec; now.tm_min = rtc->rtc_alarm.tm_min; now.tm_hour = rtc->rtc_alarm.tm_hour; ret = rtc_tm_to_time(&now, &rtc_alarm); which_alarm = RTC_ISTAT_ALARM; } else { ret = rtc_tm_to_time(&rtc->rtc_alarm, &rtc_alarm); which_alarm = RTC_ISTAT_ALARM_DAY; } if (ret == 0) { rtc_bfin_sync_pending(); bfin_write_RTC_ISTAT(which_alarm); bfin_write_RTC_ALARM(rtc_time_to_bfin(rtc_alarm)); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() | which_alarm); } spin_unlock_irq(&rtc->lock); return ret; } case RTC_AIE_OFF: stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_sync_pending(); bfin_write_RTC_ICTL(bfin_read_RTC_ICTL() & ~(RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)); spin_unlock_irq(&rtc->lock); return 0; } return -ENOIOCTLCMD; } static int bfin_rtc_read_time(struct device *dev, struct rtc_time *tm) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); spin_lock_irq(&rtc->lock); rtc_bfin_to_tm(bfin_read_RTC_STAT(), tm); spin_unlock_irq(&rtc->lock); return 0; } static int bfin_rtc_set_time(struct device *dev, struct rtc_time *tm) { struct bfin_rtc *rtc = dev_get_drvdata(dev); int ret; unsigned long now; stampit(); spin_lock_irq(&rtc->lock); ret = rtc_tm_to_time(tm, &now); if (ret == 0) { rtc_bfin_sync_pending(); bfin_write_RTC_STAT(rtc_time_to_bfin(now)); } spin_unlock_irq(&rtc->lock); return ret; } static int bfin_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); memcpy(&alrm->time, &rtc->rtc_alarm, sizeof(struct rtc_time)); alrm->pending = !!(bfin_read_RTC_ICTL() & (RTC_ISTAT_ALARM | RTC_ISTAT_ALARM_DAY)); return 0; } static int bfin_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); memcpy(&rtc->rtc_alarm, &alrm->time, sizeof(struct rtc_time)); return 0; } static int bfin_rtc_proc(struct device *dev, struct seq_file *seq) { #define yesno(x) (x ? "yes" : "no") u16 ictl = bfin_read_RTC_ICTL(); stampit(); seq_printf(seq, "alarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM)); seq_printf(seq, "wkalarm_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_ALARM_DAY)); seq_printf(seq, "seconds_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_SEC)); seq_printf(seq, "periodic_IRQ\t: %s\n", yesno(ictl & RTC_ISTAT_STOPWATCH)); #ifdef DEBUG seq_printf(seq, "RTC_STAT\t: 0x%08X\n", bfin_read_RTC_STAT()); seq_printf(seq, "RTC_ICTL\t: 0x%04X\n", bfin_read_RTC_ICTL()); seq_printf(seq, "RTC_ISTAT\t: 0x%04X\n", bfin_read_RTC_ISTAT()); seq_printf(seq, "RTC_SWCNT\t: 0x%04X\n", bfin_read_RTC_SWCNT()); seq_printf(seq, "RTC_ALARM\t: 0x%08X\n", bfin_read_RTC_ALARM()); seq_printf(seq, "RTC_PREN\t: 0x%04X\n", bfin_read_RTC_PREN()); #endif return 0; } static int bfin_irq_set_freq(struct device *dev, int freq) { struct bfin_rtc *rtc = dev_get_drvdata(dev); stampit(); rtc->rtc_dev->irq_freq = freq; return 0; } static struct rtc_class_ops bfin_rtc_ops = { .open = bfin_rtc_open, .release = bfin_rtc_release, .ioctl = bfin_rtc_ioctl, .read_time = bfin_rtc_read_time, .set_time = bfin_rtc_set_time, .read_alarm = bfin_rtc_read_alarm, .set_alarm = bfin_rtc_set_alarm, .proc = bfin_rtc_proc, .irq_set_freq = bfin_irq_set_freq, }; static int __devinit bfin_rtc_probe(struct platform_device *pdev) { struct bfin_rtc *rtc; int ret = 0; stampit(); rtc = kzalloc(sizeof(*rtc), GFP_KERNEL); if (unlikely(!rtc)) return -ENOMEM; spin_lock_init(&rtc->lock); rtc->rtc_dev = rtc_device_register(pdev->name, &pdev->dev, &bfin_rtc_ops, THIS_MODULE); if (unlikely(IS_ERR(rtc))) { ret = PTR_ERR(rtc->rtc_dev); goto err; } rtc->rtc_dev->irq_freq = 0; rtc->rtc_dev->max_user_freq = (2 << 16); /* stopwatch is an unsigned 16 bit reg */ platform_set_drvdata(pdev, rtc); return 0; err: kfree(rtc); return ret; } static int __devexit bfin_rtc_remove(struct platform_device *pdev) { struct bfin_rtc *rtc = platform_get_drvdata(pdev); rtc_device_unregister(rtc->rtc_dev); platform_set_drvdata(pdev, NULL); kfree(rtc); return 0; } static struct platform_driver bfin_rtc_driver = { .driver = { .name = "rtc-bfin", .owner = THIS_MODULE, }, .probe = bfin_rtc_probe, .remove = __devexit_p(bfin_rtc_remove), }; static int __init bfin_rtc_init(void) { stampit(); return platform_driver_register(&bfin_rtc_driver); } static void __exit bfin_rtc_exit(void) { platform_driver_unregister(&bfin_rtc_driver); } module_init(bfin_rtc_init); module_exit(bfin_rtc_exit); MODULE_DESCRIPTION("Blackfin On-Chip Real Time Clock Driver"); MODULE_AUTHOR("Mike Frysinger <[email protected]>"); MODULE_LICENSE("GPL");
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