From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit ebb22a05943666155e6da04407cc6e913974c78c ]
The recent change to validate the RTC turned out to be overly tight.
While it cures the problem on the reporters machine it breaks machines with Intel chipsets which use bit 0-5 of the D register. So check only for bit 6 being 0 which is the case on these Intel machines as well.
Fixes: 211e5db19d15 ("rtc: mc146818: Detect and handle broken RTCs") Reported-by: Serge Belyshev belyshev@depni.sinp.msu.ru Reported-by: Dirk Gouders dirk@gouders.net Reported-by: Borislav Petkov bp@suse.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Dirk Gouders dirk@gouders.net Tested-by: Len Brown len.brown@intel.com Tested-by: Borislav Petkov bp@suse.de Acked-by: Alexandre Belloni alexandre.belloni@bootlin.com Link: https://lore.kernel.org/r/87zh0nbnha.fsf@nanos.tec.linutronix.de Stable-dep-of: cd17420ebea5 ("rtc: cmos: avoid UIP when writing alarm time") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/rtc/rtc-cmos.c | 4 ++-- drivers/rtc/rtc-mc146818-lib.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index cce4b62ffdd0..8e8ce40f6440 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -808,8 +808,8 @@ 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) { + /* Ensure that the RTC is accessible. Bit 6 must be 0! */ + if ((CMOS_READ(RTC_VALID) & 0x40) != 0) { spin_unlock_irq(&rtc_lock); dev_warn(dev, "not accessible\n"); retval = -ENXIO; diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c index 7f01dc41271d..6ed2cd5d2bba 100644 --- a/drivers/rtc/rtc-mc146818-lib.c +++ b/drivers/rtc/rtc-mc146818-lib.c @@ -21,8 +21,8 @@ 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)) { + /* Ensure that the RTC is accessible. Bit 6 must be 0! */ + if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) { spin_unlock_irqrestore(&rtc_lock, flags); memset(time, 0xff, sizeof(*time)); return 0;