Problems with hwclock

This page discusses the problem with /dev/rtc on certain models.

Problem description

On bootup,a message like this shows up:

select() to /dev/rtc to wait for clock tick timed out

The RTC kernel driver can't handle the system clock.

Possible solutions

Using the --directisa switch of hwclock(8)

The hwclock command knows the parameter --directisa to access the system clock "directly" instead of accessing it by using /dev/rtc. There are several ways of doing this automatically. One is to move /sbin/hwclock (or whereever it is located on your system) to /sbin/hwclock.dist and create the following shell script, which you place at /sbin/hwclock

#!/bin/sh
/sbin/hwclock.dist --directisa $*

Make the script executable (apply the same permissions you had for hwclock before) and keep your packaging system from overwriting it on updates.

Another way of doing this is editing the initscript of hwclock (e.g., /etc/init.d/hwclock.sh in Debian) so that "--directisa" is passed as a parameter

Compiling RTC-support into the kernel instead of as a module

Compiling RTC-support (CONFIG_RTC) into the kernel instead of compiling it as a module seems to work also. Tested on: 2.6.20.6 at Thinkpad Z61m 9450-3HG

Affected Models

• Thinkpad T60
• Thinkpad T60p
• Thinkpad X60s
• Thinkpad Z61m

Affected Operating Systems

• Linux, all flavours. Tested with kernel 2.6.18, 2.6.19, 2.6.20.6