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Date:   Thu, 06 Sep 2018 02:45:04 -0700 (PDT)
Subject:     Re: [PATCH v7 0/5] riscv: Add support to no-FPU systems
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        alankao@andestech.com
From:   Palmer Dabbelt <palmer@sifive.com>
To:     alankao@andestech.com
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On Sun, 26 Aug 2018 18:07:50 PDT (-0700), alankao@andestech.com wrote:
> This patchset adds an option, CONFIG_FPU, to enable/disable floating-
> point procedures.
>
> Kernel's new behavior will be as follows:
>
> * with CONFIG_FPU=y
>   All FPU codes are reserved.  If no FPU is found during booting, a
>   global flag will be set, and those functions will be bypassed with
>   condition check to that flag.
>
> * with CONFIG_FPU=n
>   No floating-point instructions in kernel and all related settings
>   are excluded.
>
> Changes in v7:
>  - Remove "fd" attribute from KBUILD_CFLAGS.
>
> Changes in v6 (PATCH 0005 only):
>  - Make the flag checking neater.
>
> Changes in v5:
>  - Invert the polarity of checking flag from no_fpu to has_fpu.
>
> Changes in v4:
>  - Append a new patch to detect existence of FPU and followups.
>  - Add SPDX header to newly created fpu.S.
>  - Fix a build error, sorry for that.
>  - Fix wording, style, etc.
>
> Changes in v3:
>  - Refactor the whole patch into independent ones.
>
> Changes in v2:
>  - Various code cleanups and style fixes.
>
>
> Alan Kao (5):
>   Extract FPU context operations from entry.S
>   Refactor FPU code in signal setup/return procedures
>   Cleanup ISA string setting
>   Allow to disable FPU support
>   Auto-detect whether a FPU exists
>
>  arch/riscv/Kconfig                 |   9 +++
>  arch/riscv/Makefile                |  19 +++---
>  arch/riscv/include/asm/switch_to.h |  12 +++-
>  arch/riscv/kernel/Makefile         |   1 +
>  arch/riscv/kernel/cpufeature.c     |   8 +++
>  arch/riscv/kernel/entry.S          |  87 -----------------------
>  arch/riscv/kernel/fpu.S            | 106 +++++++++++++++++++++++++++++
>  arch/riscv/kernel/process.c        |   6 +-
>  arch/riscv/kernel/signal.c         |  75 ++++++++++++--------
>  9 files changed, 196 insertions(+), 127 deletions(-)
>  create mode 100644 arch/riscv/kernel/fpu.S

Thanks!  I'll add this to our for-next branch.