MC146818 support and migration from todc to rtc, guidance please

Stephen Horton SHorton at
Mon Jul 14 12:04:59 EST 2008

Hello folks,


In a current work project, I have inherited a compactPCI board that has
an mpc7447/7448 powerpc processor as well as a Marvell system
controller, model mv64462 (stripped down mv64460). The board has a
somewhat working Gentoo Linux port running on it from long ago and a
company far far away (kernel version 2.6.9 built using arch/ppc). To
prepare for an upcoming deployment, I would like to bring the OS
up-to-date on this board with a newer kernel (targeting 2.6.24).


The 2.6.9 kernel that was previously developed for the board uses the
todc.h library to enable real time clock functionality on the board's
mc146818 device. The todc library appears to have been removed during
the arch/ppc to arch/powerpc migration and replaced with a more generic
RTC mechanism.(??) I can also see that there is an
include/asm-powerpc/mc146818rtc.h file for this device included with the
2.6.24 kernel.


Can anyone give me some tips on what was intended with the removal of
the todc library? What direction should I take to port my platform file
code from todc to the new mechanism?  Is this work already done for me
in the kernel source? What work am I expected to do to add support for
this device in my kernel code? I'm specifically interested in what needs
to be included in my .dts file to enable this device.


Thanks for any guidance and advice, regards,


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