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    SubjectRe: Fwd: Commit 76a2a6ee8a0660a29127f05989ac59ae1ce865fa breaks PXA270 (at least)?
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    On Tue, 2008-07-29 at 23:56 +0100, Russell King - ARM Linux wrote:
    > On Tue, Jul 29, 2008 at 03:46:05PM -0700, Andrew Morton wrote:
    > > On Tue, 29 Jul 2008 23:31:05 +0100
    > > Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:
    > >
    > > > But then some bright spark thought it would be a good idea to get
    > > > rid of printk_clock().
    > >
    > > <does git-log, searches for printk_clock>
    > >
    > > commit 86faf39d0fc04272b05fab1db6d683f3ac7199d1
    > > Author: Ingo Molnar <mingo@elte.hu>
    > > Date: Fri Jan 25 21:07:59 2008 +0100
    > >
    > > sched: remove printk_clock references from ia64
    > >
    > > remove remaining printk_clock references from ia64.
    > >
    > > Signed-off-by: Ingo Molnar <mingo@elte.hu>
    > >
    > > commit b842271fbb9c8b5fd0e1c3e1895a3b67ba5bcc54
    > > Author: Ingo Molnar <mingo@elte.hu>
    > > Date: Fri Jan 25 21:07:59 2008 +0100
    > >
    > > sched: remove printk_clock()
    > >
    > > printk_clock() is obsolete - it has been replaced with cpu_clock().
    > >
    > > Signed-off-by: Ingo Molnar <mingo@elte.hu>
    > >
    > >
    > > That's it? It rates a 0.5/10 for changelogging :(
    > >
    > > Looking further on...
    > >
    > > commit e97126cd9056b3b42cdc862ace2ed66f8026f55b
    > > Author: Russell King <rmk@dyn-67.arm.linux.org.uk>
    > > Date: Mon Jan 8 19:49:12 2007 +0000
    > >
    > > [ARM] Provide basic printk_clock() implementation
    > >
    > > Current sched_clock() implementations on ARM cause unbootable kernels
    > > with PRINTK_TIME support enabled. To avoid this, provide a basic
    > > printk_clock() implementation which avoids sched_clock() being called
    > > before the page tables have been set up.
    > >
    > >
    > > which I assume is why arm is crashing again?
    >
    > Precisely - Ingo has effectively progressively backed out my bug fix
    > in a round-about manner by making printk require a working sched_clock
    > again.
    >
    > > Really, I think arch-overrideable printk_clock() was a good idea.
    > > printk is just _special_. It's called wildly early and it is called in
    > > all conceivable contexts and it just must work no matter what. It's
    > > totally understandable that an architecture would need to override
    > > printk's timestamp generator.
    >
    > That's one solution, the other is to have that commit reverted. I
    > don't really mind which, only that we have a solution ASAP so that
    > the current popular ARM SoCs have a bootable kernel again.

    Can't you make sched_clock() return 0 when its called before its up and
    running? Otherwise - perhaps you can play with the location of
    sched_clock_init(). cpu_clock() will return 0 before that.



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