linux-kernel - Re: [PATCH 12/13] timekeeping: default GENERIC

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Message-ID: <CAMuHMdWS5JoXho97oxcavE_OFdv+tnr+da1WV_D7sOE_YbxQxA@mail.gmail.com>
Date:   Mon, 12 Oct 2020 15:15:57 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Finn Thain <fthain@...egraphics.com.au>,
        Philip Blundell <philb@....org>,
        Joshua Thompson <funaho@...ai.org>,
        Sam Creasey <sammy@...my.net>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 12/13] timekeeping: default GENERIC_CLOCKEVENTS to enabled

On Thu, Oct 8, 2020 at 5:48 PM Arnd Bergmann <arnd@...db.de> wrote:
> Almost all machines use GENERIC_CLOCKEVENTS, so it feels wrong to
> require each one to select that symbol manually.
>
> Instead, enable it whenever CONFIG_LEGACY_TIMER_TICK is disabled as
> a simplification. It should be possible to select both
> GENERIC_CLOCKEVENTS and LEGACY_TIMER_TICK from an architecture now
> and decide at runtime between the two.
>
> For the clockevents arch-support.txt file, this means that additional
> architectures are marked as TODO when they have at least one machine
> that still uses LEGACY_TIMER_TICK, rather than being marked 'ok' when
> at least one machine has been converted. This means that both m68k and
> arm (for riscpc) revert to TODO.
>
> At this point, we could just always enable CONFIG_GENERIC_CLOCKEVENTS
> rather than leaving it off when not needed. I built an m68k
> defconfig kernel (using gcc-10.1.0) and found that this would add
> around 5.5KB in kernel image size:
>
>    text    data     bss     dec     hex filename
> 3861936 1092236  196656 5150828  4e986c obj-m68k/vmlinux-no-clockevent
> 3866201 1093832  196184 5156217  4ead79 obj-m68k/vmlinux-clockevent
>
> On Arm (MACH_RPC), that difference appears to be twice as large,
> around 11KB on top of an 6MB vmlinux.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>

>  arch/m68k/Kconfig.cpu                                |  1 -

Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds