linux-kernel - Re: [PATCH] m68knommu: fix undefined reference to `mach_get_rtc

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Message-ID: <b4757e58-fafb-c801-3c1f-6ba1c79e6b94@linux-m68k.org>
Date:   Tue, 17 May 2022 17:38:12 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Linux/m68k <linux-m68k@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] m68knommu: fix undefined reference to `mach_get_rtc_pll'

Hi Geert,

On 16/5/22 17:15, Geert Uytterhoeven wrote:
> On Mon, May 16, 2022 at 8:08 AM Greg Ungerer <gerg@...ux-m68k.org> wrote:
>> On 13/5/22 22:59, Arnd Bergmann wrote:
>>> On Fri, May 13, 2022 at 2:25 PM Greg Ungerer <gerg@...ux-m68k.org> wrote:
>>>> On 13/5/22 17:12, Geert Uytterhoeven wrote:
>>>>> read_persistent_clock64() uses mach_hwclk(), which is provided by
>>>>> both setup_mm.c and setup_no.c, so it's always available?> Albeit not populated by coldfire or nommu platform code, so I see
>>>>> the point in depending on MMU (no nommu Amiga support yet ;-).
>>>>
>>>> Yes, exactly. And even worse is that on ColdFire platforms it
>>>> is never set, so will be the startup value of NULL. It is called
>>>> without checking for NULL in both of rtc_generic_get_time() and
>>>> rtc_generic_set_time().
>>>
>>> I think that's ok because rtc_generic_{get,set}_time is only called
>>> from the rtc_generic driver, but that is not registered when mach_hwclk()
>>> is NULL.
>>>
>>> With your patch to add the CONFIG_MMU check, you can actually
>>> remove the mach_hwclk() symbol from setup_no.c, and move the
>>> remaining RTC related symbols from setup_mm.c into the #ifdef.
>>
>> Yes, I think that would be a good idea.
>> Tidies thins up a little.
> 
> Let's fix the build error first.
> 
> Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

I am re-thinking this fix at the moment. I think I missed the fact that
the 68328 has underlying mach_hwclk support, and so can use be used by
rtc_generic_{get,set}_time. So in other words classic m68k nommu config
should be able to use this code too. CONFIG_MMU blocking it is probably
not right here.

New patch coming.

Regards
Greg


> 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