linux-kernel - Re: [PATCH v1] m68k: apollo: Remove a duplicate assignment in dn_timer

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Message-ID: <CAMuHMdVCyO5JUpMExBK0OgoGfe0MYhP4WcOfrwqQkbb7FUsrxw@mail.gmail.com>
Date:   Wed, 5 Jul 2023 14:38:49 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Minjie Du <duminjie@...o.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        "open list:M68K ARCHITECTURE" <linux-m68k@...ts.linux-m68k.org>,
        open list <linux-kernel@...r.kernel.org>,
        opensource.kernel@...o.com
Subject: Re: [PATCH v1] m68k: apollo: Remove a duplicate assignment in dn_timer_int

Hi Minjie,

On Wed, Jul 5, 2023 at 2:13 PM Minjie Du <duminjie@...o.com> wrote:
> Delete a duplicate statement from this function implementation.
>
> Signed-off-by: Minjie Du <duminjie@...o.com>

Thanks for your patch, which is presumably untested on real hardware?

> --- a/arch/m68k/apollo/config.c
> +++ b/arch/m68k/apollo/config.c
> @@ -173,7 +173,6 @@ irqreturn_t dn_timer_int(int irq, void *dev_id)
>         legacy_timer_tick(1);
>         timer_heartbeat();
>
> -       x = *(volatile unsigned char *)(apollo_timer + 3);
>         x = *(volatile unsigned char *)(apollo_timer + 5);

This is intentional: the use of volatile makes sure the registers at
offsets 3 and 5 are read, in that order.

I agree this could be made more obvious by converting the code to the
more modern READ_ONCE() helper.
But please do not send such a patch without testing.

>
>         return IRQ_HANDLED;

NAKed-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