Re: [PATCH] m68k: Fix multiplatform ISA support

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Michael,

On Sun, Jun 6, 2021 at 7:28 AM Michael Schmitz <schmitzmic@gmail.com> wrote:
> Current io_mm.h uses address translation and ROM port IO primitives when
> port addresses are below 1024, and raw untranslated MMIO IO primitives
> else when CONFIG_ATARI_ROM_ISA is set. This is done regardless of the
> m68k machine type a multi-platform kernel runs on. As a consequence,
> the Q40 IDE driver in multiplatform kernels cannot work.
> Conversely, the Atari IDE driver uses wrong address translation if a
> multiplatform Q40 and Atari kernel does _not_ set CONFIG_ATARI_ROM_ISA.
>
> Replace MMIO by ISA IO primitives for addresses > 1024 (if isa_type
> is ISA_TYPE_ENEC), and change the ISA address translation used for
> Atari to a no-op for those addresses.
>
> Switch readb()/writeb() and readw()/writew() to their ISA equivalents
> also. Change the address translation functions to return the identity
> translation if CONFIG_ATARI_ROM_ISA is not defined, and set MULTI_ISA
> for kernels where Q40 and Atari are both configured so this can actually
> work (isa_type set to Q40 at compile time else).

Thanks for your patch!

> Fixes:  84b16b7b0d5c818fadc731a69965dc76dce0c91e

Fixes: 84b16b7b0d5c818f ("m68k/atari: ROM port ISA adapter support")

Hint:

    $ git help fixes
    'fixes' is aliased to 'show --format='Fixes: %h ("%s")' -s'
    $ git fixes 84b16b7b0d5c818fadc731a69965dc76dce0c91e
    Fixes: 84b16b7b0d5c818f ("m68k/atari: ROM port ISA adapter support")

> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>

> --- a/arch/m68k/include/asm/io_mm.h
> +++ b/arch/m68k/include/asm/io_mm.h
> @@ -113,7 +117,7 @@
>
>  #ifdef MULTI_ISA
>  extern int isa_type;
> -extern int isa_sex;
> +extern int isa_sex;    /* Atari relies on this to be zero-initialized */

Shouldn't that comment be next to its definition in
arch/m68k/kernel/setup_mm.c?


> @@ -135,9 +139,11 @@ static inline u8 __iomem *isa_itb(unsigned long addr)
>      case ISA_TYPE_AG: return (u8 __iomem *)AG_ISA_IO_B(addr);
>  #endif
>  #ifdef CONFIG_ATARI_ROM_ISA
> -    case ISA_TYPE_ENEC: return (u8 __iomem *)ENEC_ISA_IO_B(addr);
> +    case ISA_TYPE_ENEC: if (addr < 1024)
> +                               return (u8 __iomem *)ENEC_ISA_IO_B(addr);
> +                       fallthrough; /* not ROM port? fallback below! */
>  #endif
> -    default: return NULL; /* avoid warnings, just in case */
> +    default: return (u8 __iomem *)(addr); /* avoid warnings, just in case */
>      }

Moving the default out of the switch() statement, as suggested by Finn,
would make this more future-proof, as any case (not just the last one)
can fall through to the default, using break.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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