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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-01-31 11:40:57 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-01-31 11:40:57 -0800 |
| commit | 17b756d0376fd45f98abb6d758c3d5befb01e3fa (patch) | |
| tree | 12431c2b7db849bdd447abe1a160edd5b4aa68b1 /drivers | |
| parent | f7ea44c7172ffcc13ed589163f5168bc54f3e039 (diff) | |
| parent | 211e5db19d15a721b2953ea54b8f26c2963720eb (diff) | |
| download | linux-17b756d0376fd45f98abb6d758c3d5befb01e3fa.tar.bz2 | |
Merge tag 'timers-urgent-2021-01-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Thomas Gleixner:
"A fix for handling advertised, but non-existent 146818 RTCs correctly.
With the recent UIP handling changes the time readout of non-existent
RTCs hangs forever as the read returns always 0xFF which means the UIP
bit is set.
Sanity check the RTC before registering by checking the RTC_VALID
register for correctness"
* tag 'timers-urgent-2021-01-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rtc: mc146818: Detect and handle broken RTCs
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/rtc/rtc-cmos.c | 8 | ||||
| -rw-r--r-- | drivers/rtc/rtc-mc146818-lib.c | 7 |
2 files changed, 15 insertions, 0 deletions
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index 51e80bc70d42..68a9ac6f2fe1 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -805,6 +805,14 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq) spin_lock_irq(&rtc_lock); + /* Ensure that the RTC is accessible. Bit 0-6 must be 0! */ + if ((CMOS_READ(RTC_VALID) & 0x7f) != 0) { + spin_unlock_irq(&rtc_lock); + dev_warn(dev, "not accessible\n"); + retval = -ENXIO; + goto cleanup1; + } + if (!(flags & CMOS_RTC_FLAGS_NOFREQ)) { /* force periodic irq to CMOS reset default of 1024Hz; * diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c index 972a5b9a629d..f83c13818af3 100644 --- a/drivers/rtc/rtc-mc146818-lib.c +++ b/drivers/rtc/rtc-mc146818-lib.c @@ -21,6 +21,13 @@ unsigned int mc146818_get_time(struct rtc_time *time) again: spin_lock_irqsave(&rtc_lock, flags); + /* Ensure that the RTC is accessible. Bit 0-6 must be 0! */ + if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x7f) != 0)) { + spin_unlock_irqrestore(&rtc_lock, flags); + memset(time, 0xff, sizeof(*time)); + return 0; + } + /* * Check whether there is an update in progress during which the * readout is unspecified. The maximum update time is ~2ms. Poll |