Re: [PATCH v7 0/5] riscv: Add support to no-FPU systems

From: Palmer Dabbelt
Date: Thu Sep 06 2018 - 05:45:46 EST


On Sun, 26 Aug 2018 18:07:50 PDT (-0700), alankao@xxxxxxxxxxxxx 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.