Re: [RFC PATCH] m68k: nommu: Fix behaviour of io macros on non-CF

[Greg Ungerer <gerg@linux-m68k.org>]

Hi Daniel,

On 4/4/26 12:46, Daniel Palmer wrote:
> Currently for 68000 readl() and friends are broken in that they
> return the value from the bus as-is but should be reading a little
> endian value and swapping it to big endian.
> 
> This was found using virtio-mmio on a 68000 virt machine. virtio-mmio
> is little endian even if the emulated machine is big endian. This works
> for MMU m68k because the io macros do what is expected there, but if
> the kernel was built for nommu it breaks.
> 
> Potentially this will break some stuff for nommu non-CF m68k users
> but since there are probably 2 or 3 of us in the world I think we
> can work it out.
> 
> Suggested-by: Arnd Bergmann <arnd@kernel.org>
> Link: https://lore.kernel.org/lkml/ada73dc9-edf5-458c-8849-9f9db23ff304@app.fastmail.com/
> Signed-off-by: Daniel Palmer <daniel@0x0f.com>
> ---
>   arch/m68k/include/asm/io_no.h | 9 ---------
>   1 file changed, 9 deletions(-)
> 
> diff --git a/arch/m68k/include/asm/io_no.h b/arch/m68k/include/asm/io_no.h
> index 516371d5587a..c39db8798ef2 100644
> --- a/arch/m68k/include/asm/io_no.h
> +++ b/arch/m68k/include/asm/io_no.h
> @@ -96,15 +96,6 @@ static inline void writel(u32 value, volatile void __iomem *addr)
>   		__raw_writel(swab32(value), addr);
>   }
>   
> -#else
> -
> -#define readb __raw_readb
> -#define readw __raw_readw
> -#define readl __raw_readl
> -#define writeb __raw_writeb
> -#define writew __raw_writew
> -#define writel __raw_writel
> -
>   #endif /* IOMEMBASE */
>   
>   #if defined(CONFIG_PCI)

This change, in this form at least, breaks most of the non-MMU ColdFire targets.
Try compiling any of m5208evb, m5249evb, m5272c3, m5275evb, m5307c3 or
m5407c3 defconfigs and you get build failures. Targets that do not have
a PCI bus and so do not define IOMEMBASE will fail, which is most of them.

Maybe something like this might be better. I think this ends up giving you the
same result for 68000 nommu targets.

diff --git a/arch/m68k/include/asm/io_no.h b/arch/m68k/include/asm/io_no.h
index 516371d5587a..b335fd4a18e9 100644
--- a/arch/m68k/include/asm/io_no.h
+++ b/arch/m68k/include/asm/io_no.h
@@ -33,7 +33,6 @@
  #include <asm/byteorder.h>
  #include <asm/coldfire.h>
  #include <asm/mcfsim.h>
-#endif /* CONFIG_COLDFIRE */
  
  #if defined(IOMEMBASE)
  /*
@@ -126,6 +125,7 @@ static inline void writel(u32 value, volatile void __iomem *addr)
  #define PCI_IOBASE     ((void __iomem *) PCI_IO_PA)
  #define PCI_SPACE_LIMIT        PCI_IO_MASK
  #endif /* CONFIG_PCI */
+#endif /* CONFIG_COLDFIRE */
  
  #include <asm/kmap.h>
  #include <asm/virtconvert.h>


Regards
Greg