From f9b2a4d6a5f18e0aaf715206a056565c56889d9f Mon Sep 17 00:00:00 2001 From: Steve Muckle Date: Wed, 6 Nov 2019 11:46:25 -0800 Subject: rtc: class: support hctosys from modular RTC drivers Due to distribution constraints it may not be possible to statically compile the required RTC driver into the kernel. Expand RTC_HCTOSYS support to cover all RTC devices (statically compiled or not) by checking at the end of RTC device registration whether the time should be synced. Signed-off-by: Steve Muckle Link: https://lore.kernel.org/r/20191106194625.116692-1-smuckle@google.com Signed-off-by: Alexandre Belloni --- drivers/rtc/class.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) (limited to 'drivers/rtc/class.c') diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index 9458e6d6686a..8793b2b8cf9d 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -34,6 +34,62 @@ static void rtc_device_release(struct device *dev) #ifdef CONFIG_RTC_HCTOSYS_DEVICE /* Result of the last RTC to system clock attempt. */ int rtc_hctosys_ret = -ENODEV; + +/* IMPORTANT: the RTC only stores whole seconds. It is arbitrary + * whether it stores the most close value or the value with partial + * seconds truncated. However, it is important that we use it to store + * the truncated value. This is because otherwise it is necessary, + * in an rtc sync function, to read both xtime.tv_sec and + * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read + * of >32bits is not possible. So storing the most close value would + * slow down the sync API. So here we have the truncated value and + * the best guess is to add 0.5s. + */ + +static int rtc_hctosys(void) +{ + int err = -ENODEV; + struct rtc_time tm; + struct timespec64 tv64 = { + .tv_nsec = NSEC_PER_SEC >> 1, + }; + struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE); + + if (!rtc) { + pr_info("unable to open rtc device (%s)\n", + CONFIG_RTC_HCTOSYS_DEVICE); + goto err_open; + } + + err = rtc_read_time(rtc, &tm); + if (err) { + dev_err(rtc->dev.parent, + "hctosys: unable to read the hardware clock\n"); + goto err_read; + } + + tv64.tv_sec = rtc_tm_to_time64(&tm); + +#if BITS_PER_LONG == 32 + if (tv64.tv_sec > INT_MAX) { + err = -ERANGE; + goto err_read; + } +#endif + + err = do_settimeofday64(&tv64); + + dev_info(rtc->dev.parent, "setting system clock to %ptR UTC (%lld)\n", + &tm, (long long)tv64.tv_sec); + +err_read: + rtc_class_close(rtc); + +err_open: + rtc_hctosys_ret = err; + + return err; +} #endif #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_RTC_HCTOSYS_DEVICE) @@ -375,6 +431,11 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc) dev_info(rtc->dev.parent, "registered as %s\n", dev_name(&rtc->dev)); +#ifdef CONFIG_RTC_HCTOSYS_DEVICE + if (!strcmp(dev_name(&rtc->dev), CONFIG_RTC_HCTOSYS_DEVICE)) + rtc_hctosys(); +#endif + return 0; } EXPORT_SYMBOL_GPL(__rtc_register_device); -- cgit v1.2.3