Re: [PATCH RFC 1/2] m68k: io_mm.h: conditionalize ISA address translation on Atari

Michael Schmitz
2021-06-04T00:19:37Z

Hi Finn,

thanks for your review!

On 3/06/21 8:23 pm, Finn Thain wrote:
> On Wed, 2 Jun 2021, Michael Schmitz 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, this does fix the problem I had with CONFIG_ATARI && CONFIG_ISA.
>
>> Signed-off-by: Michael Schmity <schmitzmic@gmail.com>
> Checkpatch points out a typo here.
I noticed :-) Fat-fingered the commit in a hurry (and didn't run
checkpatch).
>
> Also, I think this should get a 'Fixes' tag so it will be backported.
I wasn't sure what to use as commit ID to be fixed ... Looks like
84b16b7b0d5c818fadc731a69965dc76dce0c91e is the one to blame. Hmm - I
thought that code was older than that...
>
>> ---
>> arch/m68k/include/asm/io_mm.h | 64 +++++++++++++++++++++++++++----------------
>> 1 file changed, 40 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/m68k/include/asm/io_mm.h b/arch/m68k/include/asm/io_mm.h
>> index d41fa48..2275e54 100644
>> --- a/arch/m68k/include/asm/io_mm.h
>> +++ b/arch/m68k/include/asm/io_mm.h
>> @@ -52,7 +52,11 @@
>> #define Q40_ISA_MEM_B(madr) (q40_isa_mem_base+1+4*((unsigned long)(madr)))
>> #define Q40_ISA_MEM_W(madr) (q40_isa_mem_base+ 4*((unsigned long)(madr)))
>>
>> +#ifdef CONFIG_ATARI
>> +#define MULTI_ISA 1
>> +#else
>> #define MULTI_ISA 0
>> +#endif /* Atari */
>> #endif /* Q40 */
>>
> I have to wonder whether there is a nice simple definition for MULTI_ISA.

As I understand it, MULTI_ISA means that different byte orders and/or
different address translations need to be used in the same kernel, so
all that cannot be decided at build time.

As long as there is only a single platform that will use this code (ISA
only used on a single platform, and neither Atari IDE nor EtherNEC
used), MULTI_ISA is not needed.

If we have Kconfig symbols for 'single platform only', and
'multi-platform ISA use', that might be shorter to write and easier to
understand. Geert?

> Such a definition would make this file a lot more easily understood. Maybe
> that flag could be implemented as a Kconfig symbol. I guess that's out of
> scope though.

That Kconfig symbol would best sit in Kconfig.machine but have to be
aware of definitions in a number of driver Kconfigs. Haven't tried if
that works. But I agree it is out of scope for now.

The question then becomes - should I move the MULTI_ISA definitions out
of the Q40 branch and out of the later Amiga Gayle PCMCIA branch to the
head of the file and add a comment explaining the rationale? Too much
churn for now?

>
>> #ifdef CONFIG_AMIGA_PCMCIA
>> @@ -135,9 +139,12 @@ 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);
>> + else
>> + return (u8 __iomem *)(addr);
> There is some trailing whitespace added here that 'git am' complains
> about.
>
> Also, I think a 'fallthrough' statement would be better than adding a new
> else branch that duplicates the new default case below.

I'm still unsure whether changing the default branch for the sake of
fixing Atari behaviour is a sane idea - I was hoping for comments either
way.

But if it's changed, you are correct that having the control flow fall
through instead of taking a redundant else branch is better.

Essentially, changing that hunk to

#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);

here (and elsewhere below)?

Cheers,

Michael

>
>> #endif
>> - default: return NULL; /* avoid warnings, just in case */
>> + default: return (u8 __iomem *)(addr); /* avoid warnings, just in case */
>> }
>> }
>> static inline u16 __iomem *isa_itw(unsigned long addr)
>> @@ -151,9 +158,12 @@ static inline u16 __iomem *isa_itw(unsigned long addr)
>> case ISA_TYPE_AG: return (u16 __iomem *)AG_ISA_IO_W(addr);
>> #endif
>> #ifdef CONFIG_ATARI_ROM_ISA
>> - case ISA_TYPE_ENEC: return (u16 __iomem *)ENEC_ISA_IO_W(addr);
>> + case ISA_TYPE_ENEC: if (addr < 1024)
>> + return (u16 __iomem *)ENEC_ISA_IO_W(addr);
>> + else
>> + return (u16 __iomem *)(addr);
>> #endif
>> - default: return NULL; /* avoid warnings, just in case */
>> + default: return (u16 __iomem *)(addr); /* avoid warnings, just in case */
> Same here.
>
>> }
>> }
>> static inline u32 __iomem *isa_itl(unsigned long addr)
>> @@ -177,9 +187,12 @@ static inline u8 __iomem *isa_mtb(unsigned long addr)
>> case ISA_TYPE_AG: return (u8 __iomem *)addr;
>> #endif
>> #ifdef CONFIG_ATARI_ROM_ISA
>> - case ISA_TYPE_ENEC: return (u8 __iomem *)ENEC_ISA_MEM_B(addr);
>> + case ISA_TYPE_ENEC: if (addr < 1024)
>> + return (u8 __iomem *)ENEC_ISA_MEM_B(addr);
>> + else
>> + return (u8 __iomem *)(addr);
>> #endif
>> - default: return NULL; /* avoid warnings, just in case */
>> + default: return (u8 __iomem *)(addr); /* avoid warnings, just in case */
> And here.
>
>> }
>> }
>> static inline u16 __iomem *isa_mtw(unsigned long addr)
>> @@ -193,9 +206,12 @@ static inline u16 __iomem *isa_mtw(unsigned long addr)
>> case ISA_TYPE_AG: return (u16 __iomem *)addr;
>> #endif
>> #ifdef CONFIG_ATARI_ROM_ISA
>> - case ISA_TYPE_ENEC: return (u16 __iomem *)ENEC_ISA_MEM_W(addr);
>> + case ISA_TYPE_ENEC: if (addr < 1024)
>> + return (u16 __iomem *)ENEC_ISA_MEM_W(addr);
>> + else
>> + return (u16 __iomem *)(addr);
>> #endif
>> - default: return NULL; /* avoid warnings, just in case */
>> + default: return (u16 __iomem *)(addr); /* avoid warnings, just in case */
> And here.
>
>> }
>> }
>>
>> @@ -344,31 +360,31 @@ static inline void isa_delay(void)
>> * ROM port ISA and everything else regular ISA for IDE. read,write defined
>> * below.
>> */
>> -#define inb(port) ((port) < 1024 ? isa_rom_inb(port) : in_8(port))
>> -#define inb_p(port) ((port) < 1024 ? isa_rom_inb_p(port) : in_8(port))
>> -#define inw(port) ((port) < 1024 ? isa_rom_inw(port) : in_le16(port))
>> -#define inw_p(port) ((port) < 1024 ? isa_rom_inw_p(port) : in_le16(port))
>> +#define inb(port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_inb(port) : isa_inb(port))
>> +#define inb_p(port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_inb_p(port) : isa_inb_p(port))
>> +#define inw(port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_inw(port) : isa_inw(port))
>> +#define inw_p(port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_inw_p(port) : isa_inw_p(port))
>> #define inl isa_inl
>> #define inl_p isa_inl_p
>>
>> -#define outb(val, port) ((port) < 1024 ? isa_rom_outb((val), (port)) : out_8((port), (val)))
>> -#define outb_p(val, port) ((port) < 1024 ? isa_rom_outb_p((val), (port)) : out_8((port), (val)))
>> -#define outw(val, port) ((port) < 1024 ? isa_rom_outw((val), (port)) : out_le16((port), (val)))
>> -#define outw_p(val, port) ((port) < 1024 ? isa_rom_outw_p((val), (port)) : out_le16((port), (val)))
>> +#define outb(val, port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outb((val), (port)) : isa_outb((val), (port)))
>> +#define outb_p(val, port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outb_p((val), (port)) : isa_outb_p((val), (port)))
>> +#define outw(val, port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outw((val), (port)) : isa_outw((val), (port)))
>> +#define outw_p(val, port) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outw_p((val), (port)) : isa_outw_p((val), (port)))
>> #define outl isa_outl
>> #define outl_p isa_outl_p
>>
>> -#define insb(port, buf, nr) ((port) < 1024 ? isa_rom_insb((port), (buf), (nr)) : isa_insb((port), (buf), (nr)))
>> -#define insw(port, buf, nr) ((port) < 1024 ? isa_rom_insw((port), (buf), (nr)) : isa_insw((port), (buf), (nr)))
>> +#define insb(port, buf, nr) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_insb((port), (buf), (nr)) : isa_insb((port), (buf), (nr)))
>> +#define insw(port, buf, nr) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_insw((port), (buf), (nr)) : isa_insw((port), (buf), (nr)))
>> #define insl isa_insl
>> -#define outsb(port, buf, nr) ((port) < 1024 ? isa_rom_outsb((port), (buf), (nr)) : isa_outsb((port), (buf), (nr)))
>> -#define outsw(port, buf, nr) ((port) < 1024 ? isa_rom_outsw((port), (buf), (nr)) : isa_outsw((port), (buf), (nr)))
>> +#define outsb(port, buf, nr) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outsb((port), (buf), (nr)) : isa_outsb((port), (buf), (nr)))
>> +#define outsw(port, buf, nr) (((port) < 1024 && ISA_TYPE == ISA_TYPE_ENEC) ? isa_rom_outsw((port), (buf), (nr)) : isa_outsw((port), (buf), (nr)))
>> #define outsl isa_outsl
>>
>> -#define readb(addr) in_8(addr)
>> -#define writeb(val, addr) out_8((addr), (val))
>> -#define readw(addr) in_le16(addr)
>> -#define writew(val, addr) out_le16((addr), (val))
>> +#define readb isa_readb
>> +#define readw isa_readw
>> +#define writeb isa_writeb
>> +#define writew isa_writew
>> #endif /* CONFIG_ATARI_ROM_ISA */
>>
>> #define readl(addr) in_le32(addr)
>>