linux-kernel - Re: [PATCH v4 0/5] riscv: Add support to no-FPU systems

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Date:   Mon, 20 Aug 2018 15:22:57 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     alankao@...estech.com
CC:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        albert@...ive.com, Christoph Hellwig <hch@...radead.org>,
        Andrew Waterman <andrew@...ive.com>,
        Arnd Bergmann <arnd@...db.de>,
        Darius Rad <darius@...espec.com>, alankao@...estech.com
Subject:     Re: [PATCH v4 0/5] riscv: Add support to no-FPU systems

On Tue, 07 Aug 2018 20:24:40 PDT (-0700), alankao@...estech.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 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/hwcap.h     |   3 +
>  arch/riscv/include/asm/switch_to.h |  21 ++++++
>  arch/riscv/kernel/Makefile         |   1 +
>  arch/riscv/kernel/cpufeature.c     |  11 +++
>  arch/riscv/kernel/entry.S          |  87 -----------------------
>  arch/riscv/kernel/fpu.S            | 106 +++++++++++++++++++++++++++++
>  arch/riscv/kernel/process.c        |   4 +-
>  arch/riscv/kernel/signal.c         |  79 +++++++++++++--------
>  10 files changed, 214 insertions(+), 126 deletions(-)
>  create mode 100644 arch/riscv/kernel/fpu.S

Aside from the CFLAGS issue this looks good.  I've queued this up in 
kernel.org/palmer/linux.git/next-nofpu, but I'm not going to put this on 
for-next until after the merge window closes.

Thanks!