Re: [PATCH V2] rtc: mc146818: Dont test for bit 0-5 in Register D

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 <redacted>
Reported-by: Dirk Gouders <redacted>
Signed-off-by: Thomas Gleixner <redacted>
---
V2: Provide the actual delta patch. Should have stayed away from
    computers today....
---
 drivers/rtc/rtc-cmos.c         |    4 ++--
 drivers/rtc/rtc-mc146818-lib.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c

@@ -805,8 +805,8 @@ cmos_do_probe(struct device *dev, struct

        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;
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c

@@ -21,8 +21,8 @@ unsigned int mc146818_get_time(struct rt

 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;