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

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Date:   Fri, 13 May 2022 14:59:24 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Greg Ungerer <gerg@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        "Linux/m68k" <linux-m68k@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] m68knommu: fix undefined reference to `mach_get_rtc_pll'

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.

       Arnd