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  1. 25 Aug, 2004 7 commits
    • Lennert Buytenhek's avatar
      [ARM PATCH] 2047/1: disable NWFPE_XP on big endian · 933d1ff5
      Lennert Buytenhek authored 
      Patch from Lennert Buytenhek

Hi,

gcc doesn't understand 80-bit floating point on the ARM currently,
according to the kernel's Kconfig docs, but it would seem that the
current extended double emulation code is broken for big endian
platforms.

So, this patch disables NWFPE_XP on big endian architectures, until
someone comes round and fixes it.


cheers,
Lennert
      933d1ff5
    • Lennert Buytenhek's avatar
      [ARM PATCH] 2046/1: fix nwfpe for double arithmetic on big-endian platforms · 6349ff20
      Lennert Buytenhek authored 
      Patch from Lennert Buytenhek

Hi,

I need the patch below (against 2.6.8-rc1-ds1) to make nwfpe properly
emulate arithmetic with doubles on a big endian ARM platform.

From reading the mailing list archives and from helpful comments I've
received from people on this list, I gather that this has come up in
the past, but it appears that Russell King was never really convinced
as to why this patch is needed.  I think I understand what's going on,
and will try to explain.

On little endian ARM, the double value 1.0 looks like this when stored
in memory in FPA word ordering:
bytes: 0x00 0x00 0xf0 0x3f 0x00 0x00 0x00 0x00
u32s:  0x3ff00000 0x00000000
u64:   0x000000003ff00000

On big endian, it looks like this:
bytes: 0x3f 0xf0 0x00 0x00 0x00 0x00 0x00 0x00
u32s:  0x3ff00000 0x00000000
u64:   0x3ff0000000000000

It appears to be this way because once upon a time, somebody decided
that the sub-words of a double will use native endian word ordering
within themselves, but the two separate words will always be stored
with the most significant one first.  God knows why they did it this
way, but they did.

Anyway.  The key observation is that nwfpe internally stores double
values in the type 'float64', which is basically just a typedef for
unsigned long long.  It never accesses 'float64's on the byte level
by casting pointers around or anything like that, it just uses direct
u64 arithmetic primitives (add, shift, or, and) for float64
manipulations and that's it.

So.  For little endian platforms, 1.0 looks like:
0x00 0x00 0xf0 0x3f 0x00 0x00 0x00 0x00
But since nwfpe treats it as a u64, it wants it to look like:
0x00 0x00 0x00 0x00 0x00 0x00 0xf0 0x3f
So, that's why the current code swaps the words around when getting
doubles from userspace and putting them back (see fpa11_cpdt.c,
loadDouble and storeDouble.)

On big endian, 1.0 looks like:
0x3f 0xf0 0x00 0x00 0x00 0x00 0x00 0x00
Since nwfpe treats it as a u64, it wants it to look like:
0x3f 0xf0 0x00 0x00 0x00 0x00 0x00 0x00
Hey!  That's exactly the same.  So in this case, it shouldn't be
swapping the halves around.  However, it currently does that swapping
unconditionally, and that's why floating point emulation messes up.

This is how I understand things -- hope it makes sense to other people
too.


cheers,
Lennert
      6349ff20
    • Ben Dooks's avatar
      [ARM PATCH] 2044/1: S3C2410 - missing IRQ_TICK from RTC resources · f43750ec
      Ben Dooks authored 
      Patch from Ben Dooks

Fixes missing IRQ_TICK from RTC resources
      f43750ec
    • Ben Dooks's avatar
      [ARM PATCH] 2043/1: S3C2410 update to registered devices · a2132900
      Ben Dooks authored 
      Patch from Ben Dooks

Updated all arch/arm/mach-s3c2410/mach-XXX.c files to
register default set of devices

Added new board struct to keep this sort of info, as it
isn't possible to register platform_devices until after
the init_io functions have been called.
      a2132900
    • Ben Dooks's avatar
      [ARM PATCH] 2042/1: S3C2410 - Clock fixes, added watchdog clock · 3ecf83f8
      Ben Dooks authored 
      Patch from Ben Dooks

Added clock definition for watchdog, and fixed it so
that clocks that cannot be enabled/disabled will be
left alone.

Fixed typo in naming of clocks when registering
      3ecf83f8
    • Russell King's avatar
      [ARM] Move DMA mask-based bounce detection to dmabounce code. · 19b6a7e4
      Russell King authored
      19b6a7e4
    • Russell King's avatar
      [ARM] Correct dma_to_virt()/virt_to_dma() return types. · 46e13d2a
      Russell King authored
      46e13d2a
  3. 24 Aug, 2004 24 commits
  5. 25 Aug, 2004 2 commits
  7. 24 Aug, 2004 7 commits
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