Re: [PATCH] LoongArch: Clean useless vcsr in loongarch_fpu.

[huqi]

On 2022/7/4 15:28, WANG Xuerui wrote:
> On 2022/7/4 14:14, huqi wrote:
> > From: Qi Hu <huqi@xxxxxxxxxxx>
> >
> > The `vcsr` do not use anymore. Remove this member from `loongarch_fpu`.
> "The VCSR is not used any more."
Thanks, this is incorrect to use `use`.
> > Signed-off-by: Qi Hu <huqi@xxxxxxxxxxx>
> > ---
> >   arch/loongarch/include/asm/fpregdef.h  |  1 -
> >   arch/loongarch/include/asm/processor.h |  2 --
> >   arch/loongarch/kernel/asm-offsets.c    |  1 -
> >   arch/loongarch/kernel/fpu.S            | 10 ----------
> >   4 files changed, 14 deletions(-)
> >
> > diff --git a/arch/loongarch/include/asm/fpregdef.h 
> > b/arch/loongarch/include/asm/fpregdef.h
> > index adb16e4b43b0..b6be527831dd 100644
> > --- a/arch/loongarch/include/asm/fpregdef.h
> > +++ b/arch/loongarch/include/asm/fpregdef.h
> > @@ -48,6 +48,5 @@
> >   #define fcsr1    $r1
> >   #define fcsr2    $r2
> >   #define fcsr3    $r3
> > -#define vcsr16    $r16
> >     #endif /* _ASM_FPREGDEF_H */
> > diff --git a/arch/loongarch/include/asm/processor.h 
> > b/arch/loongarch/include/asm/processor.h
> > index 1d63c934b289..57ec45aa078e 100644
> > --- a/arch/loongarch/include/asm/processor.h
> > +++ b/arch/loongarch/include/asm/processor.h
> > @@ -80,7 +80,6 @@ BUILD_FPR_ACCESS(64)
> >     struct loongarch_fpu {
> >       unsigned int    fcsr;
> > -    unsigned int    vcsr;
> >       uint64_t    fcc;    /* 8x8 */
> >       union fpureg    fpr[NUM_FPU_REGS];
> >   };
> > @@ -161,7 +160,6 @@ struct thread_struct {
> >        */                            \
> >       .fpu            = {                \
> >           .fcsr        = 0,                \
> > -        .vcsr        = 0,                \
> >           .fcc        = 0,                \
> >           .fpr        = {{{0,},},},            \
> >       },                            \
> > diff --git a/arch/loongarch/kernel/asm-offsets.c 
> > b/arch/loongarch/kernel/asm-offsets.c
> > index bfb65eb2844f..20cd9e16a95a 100644
> > --- a/arch/loongarch/kernel/asm-offsets.c
> > +++ b/arch/loongarch/kernel/asm-offsets.c
> > @@ -166,7 +166,6 @@ void output_thread_fpu_defines(void)
> >         OFFSET(THREAD_FCSR, loongarch_fpu, fcsr);
> >       OFFSET(THREAD_FCC,  loongarch_fpu, fcc);
> > -    OFFSET(THREAD_VCSR, loongarch_fpu, vcsr);
> >       BLANK();
> >   }
> >   diff --git a/arch/loongarch/kernel/fpu.S b/arch/loongarch/kernel/fpu.S
> > index 75c6ce0682a2..a631a7137667 100644
> > --- a/arch/loongarch/kernel/fpu.S
> > +++ b/arch/loongarch/kernel/fpu.S
> > @@ -146,16 +146,6 @@
> >       movgr2fcsr    fcsr0, \tmp0
> >       .endm
> >   -    .macro sc_save_vcsr base, tmp0
> > -    movfcsr2gr    \tmp0, vcsr16
> > -    EX    st.w \tmp0, \base, 0
> > -    .endm
> > -
> > -    .macro sc_restore_vcsr base, tmp0
> > -    EX    ld.w \tmp0, \base, 0
> > -    movgr2fcsr    vcsr16, \tmp0
> > -    .endm
> > -
> >   /*
> >    * Save a thread's fp context.
> >    */
>
> The original code was written with future LSX/LASX support in mind; 
> the code is dead currently, but expected to get utilized Soon (TM).
>
> So, I'd like to confirm if future LoongArch models would *not* feature 
> LSX/LASX in its current form, and that the Loongson Corporation is not 
> going to upstream LSX/LASX support, given you are apparently a 
> Loongson employee with the first-hand information? We'd like to avoid 
> code churn in general, so if the LSX/LASX support is to be eventually 
> mainlined, removing them now would only lead to them being introduced 
> later.

`vcsr` is removed because it has been removed in hardware. What's more, 
it will not be used to support LSX/LASX in the future.