linux-kernel - Re: [PATCH] power: reset: ltc2952: fix float conversion error

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Date:   Tue, 7 Dec 2021 12:05:57 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Sebastian Reichel <sre@...nel.org>,
        René Moll <Rene.Moll@...ns.com>,
        Arnd Bergmann <arnd@...db.de>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] power: reset: ltc2952: fix float conversion error

On Tue, Dec 07, 2021 at 10:41:24AM -0800, Nick Desaulniers wrote:
> On Sat, Dec 4, 2021 at 2:02 PM Arnd Bergmann <arnd@...nel.org> wrote:
> >
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > clang-14 does not like the way this driver converts a 'long double'
> > to an integer when the target architecture disables floating point
> > support:
> >
> > drivers/power/reset/ltc2952-poweroff.c:162:28: error: expression requires  'long double' type support, but target 'x86_64-unknown-linux' does not support it
> >         data->wde_interval = 300L * 1E6L;
> >                                   ^
> >
> > Turn this into pure integer math and make it more readable at the
> > same time using the NSEC_PER_MSEC macro instead.
> >
> > Fixes: 6647156c00cc ("power: reset: add LTC2952 poweroff driver")
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> Thanks for the patch! The change in clang-14 (ToT) that triggered this
> has had another patch on top reverting these diagnostics.
> https://reviews.llvm.org/D114162

I can still reproduce this failure on current ToT (33e3554ea33d) on
x86_64 allmodconfig; it seems like that patch only fixes it for 32-bit
x86.

> That said, this change is still worthwhile for the improved semantics, IMO.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1497
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

My patch appears to be accepted in Sebastian's branch already, it seems
like it just needs to be sent to Linus (it also looks like that branch
doesn't flow into -next, it probably should):

https://git.kernel.org/sre/linux-power-supply/c/644106cdb89844be2496b21175b7c0c2e0fab381

Cheers,
Nathan

> > ---
> >  drivers/power/reset/ltc2952-poweroff.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/power/reset/ltc2952-poweroff.c b/drivers/power/reset/ltc2952-poweroff.c
> > index fbb344353fe4..9fc88a9f244c 100644
> > --- a/drivers/power/reset/ltc2952-poweroff.c
> > +++ b/drivers/power/reset/ltc2952-poweroff.c
> > @@ -159,8 +159,8 @@ static void ltc2952_poweroff_kill(void)
> >
> >  static void ltc2952_poweroff_default(struct ltc2952_poweroff *data)
> >  {
> > -       data->wde_interval = 300L * 1E6L;
> > -       data->trigger_delay = ktime_set(2, 500L*1E6L);
> > +       data->wde_interval = 300 * NSEC_PER_MSEC;
> > +       data->trigger_delay = ktime_set(2, 500 * NSEC_PER_MSEC);
> >
> >         hrtimer_init(&data->timer_trigger, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> >         data->timer_trigger.function = ltc2952_poweroff_timer_trigger;
> > --
> > 2.29.2
> >
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers