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Bug 158781 - ppc64: Kernel Panic on I2C Bus in New Apple G5 Logic Board < 2.6.12
Summary: ppc64: Kernel Panic on I2C Bus in New Apple G5 Logic Board < 2.6.12
Alias: None
Product: Fedora
Classification: Fedora
Component: kernel
Version: 4
Hardware: powerpc
OS: Linux
Target Milestone: ---
Assignee: David Woodhouse
QA Contact: Brian Brock
Depends On:
TreeView+ depends on / blocked
Reported: 2005-05-25 17:42 UTC by Daniel Shay
Modified: 2007-11-30 22:11 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2005-06-04 05:37:23 UTC

Attachments (Terms of Use)

Description Daniel Shay 2005-05-25 17:42:39 UTC
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.8) Gecko/20050511 Firefox/1.0.4

Description of problem:
Kernel problems related to the newest revision of the Apple G5 Dual Processor Systems.


Benjamin Herrenschmidt <>:
    [PATCH] ppc64: Fix booting on latest G5 models

    The latest speedbumped Apple G5 models have a "bug" in the Open Firmware
    device tree that lacks the proper interrupt routing information for the
    northbridge i2c controller.  Apple's driver silently falls back into a
    sub-optimal "polled" mode (heh, maybe they didn't even notice the bug
    because of that :), our driver didn't properly check and crashes :(

    This patch fixes our driver to not crash, and adds code to the
    prom_init() OF trampoline code that detects the "bug" and adds the
    missing information back for this chipset revision.  This fixes booting
    and thermal control on these models.

    Signed-off-by: Benjamin Herrenschmidt <>
    Signed-off-by: Linus Torvalds <>

Benjamin Herrenschmidt <>:
    [PATCH] ppc64: Fix g5 hw timebase sync

    The hardware sync of the timebase on SMP G5s uses a black magic
    incantation to the i2c clock chip that was inspired from what Darwin

    However, this was an earlier version of Darwin that was ...  buggy !
    heh.  This causes the latest models to break though when starting SMP,
    so it's worth fixing.

    Here's a new version of the incantation based on careful transcription
    of the said incantations as found in the latest version of apple's

    Signed-off-by: Benjamin Herrenschmidt <>
    Signed-off-by: Linus Torvalds <>

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.Boot any Linux PPC64 Kernel < 2.6.12
2.Kernel Panic After I2C Probe

Additional info:

Comment 1 Dave Jones 2005-05-27 00:34:25 UTC
The kernel in rawhide today should have this fixed, as it includes -rc5

Comment 2 Daniel Shay 2005-06-02 21:16:10 UTC
Installed and running 2.6.11-1.1366_FC4-ppc from the rawhide yesterday 06/01/2005.


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