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    SubjectRe: [PATCH] clocksource: sh_tmu: Set cpu_possible_mask to fix SMP broadcast
    Date
    Hi Magnus,

    On Tuesday 16 December 2014 20:46:33 Magnus Damm wrote:
    > On Tue, Dec 16, 2014 at 8:20 PM, Laurent Pinchart wrote:
    > > On Tuesday 16 December 2014 12:14:40 Daniel Lezcano wrote:
    > >> On 12/16/2014 10:48 AM, Magnus Damm wrote:
    > >> > From: Magnus Damm <damm+renesas@opensource.se>
    > >> >
    > >> > Update the TMU driver to use cpu_possible_mask as cpumask to make
    > >> > r8a7779 SMP work as expected with or without the ARM TWD timer.
    > >> >
    > >> > Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
    > >>
    > >> Applied as a 3.18 fix.
    > >
    > > You're a bit too fast, I haven't had time to review the patch yet.
    > >
    > >> ps: May I suggest to use the CLOCK_EVT_FEAT_DYNIRQ flag for this driver ?
    > >>
    > >> > ---
    > >> >
    > >> > drivers/clocksource/sh_tmu.c | 2 +-
    > >> > 1 file changed, 1 insertion(+), 1 deletion(-)
    > >> >
    > >> > --- 0001/drivers/clocksource/sh_tmu.c
    > >> > +++ work/drivers/clocksource/sh_tmu.c 2014-12-16
    > >> > 17:49:49.000000000 +0900 @@ -428,7 +428,7 @@ static void
    > >> > sh_tmu_register_clockevent(s
    > >> > ced->features = CLOCK_EVT_FEAT_PERIODIC;
    > >> > ced->features |= CLOCK_EVT_FEAT_ONESHOT;
    > >> > ced->rating = 200;
    > >> > - ced->cpumask = cpumask_of(0);
    > >> > + ced->cpumask = cpu_possible_mask;
    > >
    > > Magnus, how thoroughly have you tested this ? The TMU is indeed usable by
    > > all CPUs, so setting the CPU mask to cpu_possible_mask makes sense, but
    > > last time I've tried that it broke the broadcast timer due to the
    > > heuristics used by the clock events core code.
    >
    > Uhm, so I've tested this particular patch on r8a7779 but I do agree
    > that the TMU is used on a bunch of SoCs if that's what you mean. I
    > don't see how it is different from any other of our timers though, and
    > those got fixed like this earlier.
    >
    > I wonder if you may recall an earlier issue with incorrect clock event
    > priorities and code somehow working-by-accident without the mask set
    > as expected?

    As discussed privately today, I've had this exact same patch in one of my
    private branches, and I haven't pushed it upstream at the same time as the
    similar cmt and mtu2 patches due to a regression. Unfortunately I don't
    remember the details :-/

    I'll test the patch on Marzen and KZM9G. I unfortunately can't test it on
    Armadillo as I don't have access to that board anymore.

    > > Could you please confirm that you've tested both CONFIG_PREEMPT_NONE and
    > > CONFIG_PREEMPT with and without the ARM TWD times, and that you've booted
    > > to userspace and tested timer broadcast on all CPUs ?
    >
    > No I have not. I've booted to user space in initramfs with DT-based
    > TWD on Multiplatform for r8a7779. Without this fix (and other r8a7779
    > TWD bits) I see a lot of breakage. For instance, TWD and SMP boot is
    > broken on r8a7779 - both legacy and non-legacy. I have not gotten to
    > sh73a0 yet, but I assume it is busted too.
    >
    > Can you please explain to me how the TMU is any different compared to
    > the CMT, MTU2 or STI? =)

    I don't know yet :-) I'll hopefully have more information after testing on
    KZM9G.

    > And no, I don't have any r8a7740 board anymore. Can anyone else test?

    --
    Regards,

    Laurent Pinchart



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