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Re: [Qemu-arm] [PATCH v17 00/14] PTimer fixes/features and ARM MPTimer c

From: Peter Maydell
Subject: Re: [Qemu-arm] [PATCH v17 00/14] PTimer fixes/features and ARM MPTimer conversion
Date: Mon, 24 Oct 2016 13:23:17 +0100

On 2 October 2016 at 16:53, Dmitry Osipenko <address@hidden> wrote:
> Hello,
> Currently, QEMU ARM MPTimer device model provides only a certain subset of
> the emulation behavior. This patch series is supposed to add missing parts by
> converting the MPTimer to use generic ptimer helper. It fixes some important
> ptimer bugs and provides new features that are required for the ARM MPTimer.
> WARNING! I based V17 on top of the Paolo's patch [0], however I don't see
> the original mail of that patch on the ML nor in patches/patchew.
> [0] https://lists.nongnu.org/archive/html/qemu-devel/2016-09/msg06734.html

Looking at the code we end up with in ptimer, we seem to do an
awful lot of adding and subtracting 1 everywhere. That makes me
wonder if we're missing a simplification which would collapse
all of those out (it seems unlikely that hardware would really
ever want some of the policy flags but not all of them, since
I think they boil down to "timer==0 is a real one-timer-cycle
lump of time").

That said, I think the behaviour is right and this patchseries has
been around way too long already, so I've applied it to target-arm.next.
If we can think of a simplification we can always apply it later
as a refactoring with a fair degree of confidence given the tests...

-- PMM

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