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![John Stultz](/assets/img/avatar_default.png)
When we register an rtc device at boot, we read the alarm value in hardware and set the rtc device's aie_timer to that value. The initial method to do this was to simply call rtc_set_alarm() with the value read from hardware. However, this may cause problems as rtc_set_alarm may enable interupts, and the RTC alarm might fire, which can cause invalid pointer dereferencing since the RTC registration is not complete. This patch solves the issue by initializing the rtc_device.aie_timer y hand via rtc_initialize_alarm(). This avoids any calls to the RTC hardware which might enable interrupts too early. CC: Thomas Gleixner <tglx@linutronix.de> CC: Alessandro Zummo <a.zummo@towertech.it> Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: John Stultz <john.stultz@linaro.org>
261 lines
5.9 KiB
C
261 lines
5.9 KiB
C
/*
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* RTC subsystem, base class
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*
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* Copyright (C) 2005 Tower Technologies
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* Author: Alessandro Zummo <a.zummo@towertech.it>
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*
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* class skeleton from drivers/hwmon/hwmon.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/rtc.h>
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#include <linux/kdev_t.h>
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#include <linux/idr.h>
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#include <linux/slab.h>
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#include <linux/workqueue.h>
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#include "rtc-core.h"
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static DEFINE_IDR(rtc_idr);
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static DEFINE_MUTEX(idr_lock);
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struct class *rtc_class;
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static void rtc_device_release(struct device *dev)
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{
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struct rtc_device *rtc = to_rtc_device(dev);
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mutex_lock(&idr_lock);
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idr_remove(&rtc_idr, rtc->id);
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mutex_unlock(&idr_lock);
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kfree(rtc);
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}
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#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
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/*
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* On suspend(), measure the delta between one RTC and the
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* system's wall clock; restore it on resume().
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*/
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static struct timespec delta;
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static time_t oldtime;
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static int rtc_suspend(struct device *dev, pm_message_t mesg)
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{
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struct rtc_device *rtc = to_rtc_device(dev);
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struct rtc_time tm;
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struct timespec ts = current_kernel_time();
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if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
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return 0;
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rtc_read_time(rtc, &tm);
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rtc_tm_to_time(&tm, &oldtime);
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/* RTC precision is 1 second; adjust delta for avg 1/2 sec err */
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set_normalized_timespec(&delta,
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ts.tv_sec - oldtime,
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ts.tv_nsec - (NSEC_PER_SEC >> 1));
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return 0;
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}
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static int rtc_resume(struct device *dev)
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{
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struct rtc_device *rtc = to_rtc_device(dev);
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struct rtc_time tm;
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time_t newtime;
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struct timespec time;
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if (strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE) != 0)
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return 0;
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rtc_read_time(rtc, &tm);
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if (rtc_valid_tm(&tm) != 0) {
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pr_debug("%s: bogus resume time\n", dev_name(&rtc->dev));
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return 0;
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}
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rtc_tm_to_time(&tm, &newtime);
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if (newtime <= oldtime) {
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if (newtime < oldtime)
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pr_debug("%s: time travel!\n", dev_name(&rtc->dev));
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return 0;
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}
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/* restore wall clock using delta against this RTC;
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* adjust again for avg 1/2 second RTC sampling error
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*/
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set_normalized_timespec(&time,
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newtime + delta.tv_sec,
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(NSEC_PER_SEC >> 1) + delta.tv_nsec);
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do_settimeofday(&time);
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return 0;
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}
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#else
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#define rtc_suspend NULL
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#define rtc_resume NULL
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#endif
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/**
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* rtc_device_register - register w/ RTC class
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* @dev: the device to register
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*
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* rtc_device_unregister() must be called when the class device is no
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* longer needed.
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*
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* Returns the pointer to the new struct class device.
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*/
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struct rtc_device *rtc_device_register(const char *name, struct device *dev,
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const struct rtc_class_ops *ops,
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struct module *owner)
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{
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struct rtc_device *rtc;
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struct rtc_wkalrm alrm;
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int id, err;
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if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) {
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err = -ENOMEM;
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goto exit;
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}
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mutex_lock(&idr_lock);
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err = idr_get_new(&rtc_idr, NULL, &id);
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mutex_unlock(&idr_lock);
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if (err < 0)
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goto exit;
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id = id & MAX_ID_MASK;
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rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);
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if (rtc == NULL) {
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err = -ENOMEM;
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goto exit_idr;
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}
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rtc->id = id;
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rtc->ops = ops;
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rtc->owner = owner;
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rtc->irq_freq = 1;
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rtc->max_user_freq = 64;
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rtc->dev.parent = dev;
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rtc->dev.class = rtc_class;
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rtc->dev.release = rtc_device_release;
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mutex_init(&rtc->ops_lock);
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spin_lock_init(&rtc->irq_lock);
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spin_lock_init(&rtc->irq_task_lock);
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init_waitqueue_head(&rtc->irq_queue);
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/* Init timerqueue */
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timerqueue_init_head(&rtc->timerqueue);
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INIT_WORK(&rtc->irqwork, rtc_timer_do_work);
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/* Init aie timer */
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rtc_timer_init(&rtc->aie_timer, rtc_aie_update_irq, (void *)rtc);
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/* Init uie timer */
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rtc_timer_init(&rtc->uie_rtctimer, rtc_uie_update_irq, (void *)rtc);
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/* Init pie timer */
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hrtimer_init(&rtc->pie_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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rtc->pie_timer.function = rtc_pie_update_irq;
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rtc->pie_enabled = 0;
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/* Check to see if there is an ALARM already set in hw */
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err = __rtc_read_alarm(rtc, &alrm);
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if (!err && !rtc_valid_tm(&alrm.time))
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rtc_initialize_alarm(rtc, &alrm);
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strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE);
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dev_set_name(&rtc->dev, "rtc%d", id);
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rtc_dev_prepare(rtc);
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err = device_register(&rtc->dev);
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if (err) {
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put_device(&rtc->dev);
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goto exit_kfree;
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}
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rtc_dev_add_device(rtc);
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rtc_sysfs_add_device(rtc);
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rtc_proc_add_device(rtc);
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dev_info(dev, "rtc core: registered %s as %s\n",
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rtc->name, dev_name(&rtc->dev));
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return rtc;
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exit_kfree:
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kfree(rtc);
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exit_idr:
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mutex_lock(&idr_lock);
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idr_remove(&rtc_idr, id);
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mutex_unlock(&idr_lock);
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exit:
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dev_err(dev, "rtc core: unable to register %s, err = %d\n",
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name, err);
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return ERR_PTR(err);
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}
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EXPORT_SYMBOL_GPL(rtc_device_register);
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/**
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* rtc_device_unregister - removes the previously registered RTC class device
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*
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* @rtc: the RTC class device to destroy
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*/
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void rtc_device_unregister(struct rtc_device *rtc)
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{
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if (get_device(&rtc->dev) != NULL) {
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mutex_lock(&rtc->ops_lock);
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/* remove innards of this RTC, then disable it, before
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* letting any rtc_class_open() users access it again
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*/
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rtc_sysfs_del_device(rtc);
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rtc_dev_del_device(rtc);
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rtc_proc_del_device(rtc);
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device_unregister(&rtc->dev);
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rtc->ops = NULL;
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mutex_unlock(&rtc->ops_lock);
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put_device(&rtc->dev);
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}
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}
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EXPORT_SYMBOL_GPL(rtc_device_unregister);
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static int __init rtc_init(void)
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{
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rtc_class = class_create(THIS_MODULE, "rtc");
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if (IS_ERR(rtc_class)) {
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printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
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return PTR_ERR(rtc_class);
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}
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rtc_class->suspend = rtc_suspend;
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rtc_class->resume = rtc_resume;
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rtc_dev_init();
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rtc_sysfs_init(rtc_class);
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return 0;
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}
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static void __exit rtc_exit(void)
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{
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rtc_dev_exit();
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class_destroy(rtc_class);
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idr_destroy(&rtc_idr);
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}
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subsys_initcall(rtc_init);
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module_exit(rtc_exit);
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MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
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MODULE_DESCRIPTION("RTC class support");
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MODULE_LICENSE("GPL");
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