On Thu, Jan 4, 2024 at 11:58 PM Samuel Holland
[off-list ref] wrote:

Hi Huacai,

On 2024-01-04 3:55 AM, Huacai Chen wrote:

quoted

Hi, Samuel,

On Thu, Dec 28, 2023 at 9:42 AM Samuel Holland
[off-list ref] wrote:

quoted

LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in
asm/fpu.h, so it only needs to add kernel_fpu_available() and export
the CFLAGS adjustments.

Acked-by: WANG Xuerui <redacted>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v1)

 arch/loongarch/Kconfig           | 1 +
 arch/loongarch/Makefile          | 5 ++++-
 arch/loongarch/include/asm/fpu.h | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index ee123820a476..65d4475565b8 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig

@@ -15,6 +15,7 @@ config LOONGARCH
        select ARCH_HAS_CPU_FINALIZE_INIT
        select ARCH_HAS_FORTIFY_SOURCE
        select ARCH_HAS_KCOV
+       select ARCH_HAS_KERNEL_FPU_SUPPORT if CPU_HAS_FPU
        select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
        select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
        select ARCH_HAS_PTE_SPECIAL

diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 4ba8d67ddb09..1afe28feaba5 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile

@@ -25,6 +25,9 @@ endif
 32bit-emul             = elf32loongarch
 64bit-emul             = elf64loongarch

+CC_FLAGS_FPU           := -mfpu=64
+CC_FLAGS_NO_FPU                := -msoft-float

We will add LoongArch32 support later, maybe it should be -mfpu=32 in
that case, and do other archs have the case that only support FP32?

Do you mean that LoongArch32 does not support double-precision FP in hardware?
At least both of the consumers in this series use double-precision, so my first
thought is that LoongArch32 could not select ARCH_HAS_KERNEL_FPU_SUPPORT.

Then is it possible to introduce CC_FLAGS_SP_FPU and CC_FLAGS_DP_FPU?
I think there may be some place where SP FP is enough.

Huacai

Regards,
Samuel