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From:   Greentime Hu <green.hu@gmail.com>
Date:   Thu, 22 Nov 2018 18:21:02 +0800
Message-ID: <CAEbi=3eNDRLAOWiXSXyAbDot9TosNRb+-qdsLB6sCSzeGnB2+w@mail.gmail.com>
Subject: Re: [PATCH v4 0/5] nds32 FPU port
To:     Vincent Chen <vincentc@andestech.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Vincent Chen <vincentc@andestech.com> =E6=96=BC 2018=E5=B9=B411=E6=9C=8822=
=E6=97=A5 =E9=80=B1=E5=9B=9B =E4=B8=8A=E5=8D=8811:14=E5=AF=AB=E9=81=93=EF=
=BC=9A
>
>   This patch set contains basic components for supporting the nds32 FPU,
> such as exception handlers and context switch for FPU registers. By
> default, the lazy FPU scheme is supported and the user can configure it
> via CONFIG_LZAY_FPU. In addition, a floating point emulator is required
> to handle all arithmetic of denormalized number because it is not support=
ed
> by the nds32 FPU.
>
>   As mentioned above, the nds32 FPU does not support denormalized number
> This means the denormalized operands and results are not permitted. If an
> instruction contains denormalized operands, the nds32 FPU will raise an
> denormalized input exception to inform kernel to deal with this
> instruction. If the result of the instruction is a denormalized number,
> normally nds32 FPU will treat it as an underflow case and round the resul=
t
> to an appropriate value based on current rounding mode. Obviously, there =
is
> a precision gap for tininess number. To reduce this precision gap, kernel
> will enable the underflow trap by default to direct all underflow cases t=
o
> the floating pointer emulator. By the floating pointer emulator, the
> correct denormalized number can be derived in kernel and return to the us=
er
> program. The feature can be configured by
> CONFIG_SUPPORT_DENORMAL_ARITHMETIC, and if the precision requirement is n=
ot
> critical for tininess number, user may disables this feature to keep
> performance.
>
>   The implementation of floating point emulator is based on soft-fp
> which is located in include/math-emu folder. However, soft-fp is too
> outdated to pass the current compiler check. The needed modifications
> for soft-fp are included in this patch set
>
> Changes in v4:
>  - Fix compilation error
>
> Changes in v3:
>  - Kernel with FPU support enabled still can run on a CPU without FPU
>  - Rename CONFIG_UNLAZY_FPU to CONFIG_LAYZ_FPU
>  - Rename _switch() to _switch_fpu()
>  - Store FPU context when kernel suspends
>  - Modify the comments in code and patch
>
> Changes in v2:
>  - Remove the initilzation for floating pointer register before entering =
to
>    signal handler.
>
> Vincent Chen (5):
>   nds32: nds32 FPU port
>   nds32: Support FP emulation
>   nds32: support denormalized result through FP emulator
>   math-emu/op-2.h: Use statement expressions to prevent negative
>     constant shift
>   math-emu/soft-fp.h: (_FP_ROUND_ZERO) cast 0 to void to fix warning
>
>  arch/nds32/Kconfig                       |    1 +
>  arch/nds32/Kconfig.cpu                   |   34 +++
>  arch/nds32/Makefile                      |    5 +
>  arch/nds32/include/asm/bitfield.h        |   15 ++
>  arch/nds32/include/asm/elf.h             |   11 +
>  arch/nds32/include/asm/fpu.h             |  126 +++++++++++
>  arch/nds32/include/asm/fpuemu.h          |   32 +++
>  arch/nds32/include/asm/nds32_fpu_inst.h  |  109 +++++++++
>  arch/nds32/include/asm/processor.h       |    7 +
>  arch/nds32/include/asm/sfp-machine.h     |  158 +++++++++++++
>  arch/nds32/include/asm/syscalls.h        |    1 +
>  arch/nds32/include/uapi/asm/auxvec.h     |    7 +
>  arch/nds32/include/uapi/asm/sigcontext.h |   14 ++
>  arch/nds32/include/uapi/asm/udftrap.h    |   13 +
>  arch/nds32/include/uapi/asm/unistd.h     |    2 +
>  arch/nds32/kernel/Makefile               |    4 +
>  arch/nds32/kernel/ex-entry.S             |   24 ++-
>  arch/nds32/kernel/ex-exit.S              |   13 +-
>  arch/nds32/kernel/ex-scall.S             |    8 +-
>  arch/nds32/kernel/fpu.c                  |  269 ++++++++++++++++++++++
>  arch/nds32/kernel/process.c              |   64 +++++-
>  arch/nds32/kernel/setup.c                |   12 +-
>  arch/nds32/kernel/signal.c               |   62 +++++-
>  arch/nds32/kernel/sleep.S                |    4 +-
>  arch/nds32/kernel/sys_nds32.c            |   32 +++
>  arch/nds32/kernel/traps.c                |   16 ++
>  arch/nds32/math-emu/Makefile             |    7 +
>  arch/nds32/math-emu/faddd.c              |   24 ++
>  arch/nds32/math-emu/fadds.c              |   24 ++
>  arch/nds32/math-emu/fcmpd.c              |   24 ++
>  arch/nds32/math-emu/fcmps.c              |   24 ++
>  arch/nds32/math-emu/fd2s.c               |   22 ++
>  arch/nds32/math-emu/fdivd.c              |   27 +++
>  arch/nds32/math-emu/fdivs.c              |   26 +++
>  arch/nds32/math-emu/fmuld.c              |   23 ++
>  arch/nds32/math-emu/fmuls.c              |   23 ++
>  arch/nds32/math-emu/fnegd.c              |   21 ++
>  arch/nds32/math-emu/fnegs.c              |   21 ++
>  arch/nds32/math-emu/fpuemu.c             |  357 ++++++++++++++++++++++++=
++++++
>  arch/nds32/math-emu/fs2d.c               |   23 ++
>  arch/nds32/math-emu/fsqrtd.c             |   21 ++
>  arch/nds32/math-emu/fsqrts.c             |   21 ++
>  arch/nds32/math-emu/fsubd.c              |   27 +++
>  arch/nds32/math-emu/fsubs.c              |   27 +++
>  include/math-emu/op-2.h                  |   97 ++++-----
>  include/math-emu/soft-fp.h               |    2 +-
>  46 files changed, 1816 insertions(+), 68 deletions(-)
>  create mode 100644 arch/nds32/include/asm/fpu.h
>  create mode 100644 arch/nds32/include/asm/fpuemu.h
>  create mode 100644 arch/nds32/include/asm/nds32_fpu_inst.h
>  create mode 100644 arch/nds32/include/asm/sfp-machine.h
>  create mode 100644 arch/nds32/include/uapi/asm/udftrap.h
>  create mode 100644 arch/nds32/kernel/fpu.c
>  create mode 100644 arch/nds32/math-emu/Makefile
>  create mode 100644 arch/nds32/math-emu/faddd.c
>  create mode 100644 arch/nds32/math-emu/fadds.c
>  create mode 100644 arch/nds32/math-emu/fcmpd.c
>  create mode 100644 arch/nds32/math-emu/fcmps.c
>  create mode 100644 arch/nds32/math-emu/fd2s.c
>  create mode 100644 arch/nds32/math-emu/fdivd.c
>  create mode 100644 arch/nds32/math-emu/fdivs.c
>  create mode 100644 arch/nds32/math-emu/fmuld.c
>  create mode 100644 arch/nds32/math-emu/fmuls.c
>  create mode 100644 arch/nds32/math-emu/fnegd.c
>  create mode 100644 arch/nds32/math-emu/fnegs.c
>  create mode 100644 arch/nds32/math-emu/fpuemu.c
>  create mode 100644 arch/nds32/math-emu/fs2d.c
>  create mode 100644 arch/nds32/math-emu/fsqrtd.c
>  create mode 100644 arch/nds32/math-emu/fsqrts.c
>  create mode 100644 arch/nds32/math-emu/fsubd.c
>  create mode 100644 arch/nds32/math-emu/fsubs.c

Hi Vincent,

Thank you.

Acked-by: Greentime Hu <greentime@andestech.com>