Re: [PATCH] m68k: Fix multiplatform ISA support

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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@xxxxxxxxx> 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@xxxxxxxxx>

--- 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@xxxxxxxxxxxxxx

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




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