Re: [PATCH] m68k: Fix multiplatform ISA support

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Geert,

thanks for your review!

Am 07.06.2021 um 19:49 schrieb Geert Uytterhoeven:
> 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")

Thanks, I'll change that.

>> 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?

I ended up dropping changes to that file, and would rather omit the 
comment here than touching setup_mm.c just for the sake of adding a 
comment.

We might omit the isa_sex = 0 stuff in setup_mm.c altogether, OTOH ...

>
>> @@ -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.

OK, I take that to indicate the default may be changed in that way, and 
will move it outside the switch().

Cheers,

	Michael


>
> 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
>