linux-kernel - Re: [PATCH] LoongArch: Clean useless vcsr in loongarch

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Message-ID: <e187cda4edf0a3186e7caae8ed285e2564742f26.camel@xry111.site>
Date:   Mon, 04 Jul 2022 17:58:57 +0800
From:   Xi Ruoyao <xry111@...111.site>
To:     huqi <huqi@...ngson.cn>, WANG Xuerui <kernel@...0n.name>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Clean useless vcsr in loongarch_fpu.

On Mon, 2022-07-04 at 17:27 +0800, huqi wrote:

> 
> > 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.

It would be better to add this information into the commit message.  Is
it already removed in 3A5000?  On my machine "movfcsr2gr $a0, $r16"
produces SIGILL (but maybe it's because LSX is not enabled via the EUEN
register).

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University