On 2/19/22 12:27 AM, Mateusz Jończyk wrote:
Some problems with reading the RTC time may happen rarely, for example
while the RTC is updating. So read the RTC many times to catch these
problems. For example, a previous attempt for my
commit ea6fa4961aab ("rtc: mc146818-lib: fix RTC presence check")
was incorrect and would have triggered this selftest.
To avoid the risk of damaging the hardware, wait 11ms before consecutive
reads.
In rtc_time_to_timestamp I copied values manually instead of casting -
just to be on the safe side. The 11ms wait period was chosen so that it is
not a divisor of 1000ms.
Signed-off-by: Mateusz Jończyk <mat.jonczyk@xxxxx>
Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
---
Also, before
commit cdedc45c579f ("rtc: cmos: avoid UIP when reading alarm time")
reading the RTC alarm time during RTC update produced incorrect results
on many Intel platforms. Preparing a similar selftest for this case
would be more difficult, though, because the RTC alarm time is cached by
the kernel. Direct access would have to be exposed somehow, for example
in debugfs. I may prepare a patch for it in the future.
---
Looks good to me. We end up tweaking the timeout=210 in settings every
now and then. Not sure how we can avoid adjusting it as we find problems.
I will apply this in for Linux 5.18-rc1
thanks,
-- Shuah
