linux-kernel - Re: [PATCH 12/19] riscv: Create xtheadvector file

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Message-ID: <20240412-thirty-sacrament-db052c7fe6fe@wendy>
Date: Fri, 12 Apr 2024 12:30:32 +0100
From: Conor Dooley <conor.dooley@...rochip.com>
To: Charlie Jenkins <charlie@...osinc.com>
CC: Conor Dooley <conor@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>, Jernej Skrabec
	<jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, Evan Green
	<evan@...osinc.com>, Clément Léger
	<cleger@...osinc.com>, Jonathan Corbet <corbet@....net>, Shuah Khan
	<shuah@...nel.org>, <linux-riscv@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Palmer Dabbelt
	<palmer@...osinc.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-sunxi@...ts.linux.dev>, <linux-doc@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 12/19] riscv: Create xtheadvector file

On Thu, Apr 11, 2024 at 09:11:18PM -0700, Charlie Jenkins wrote:
> These definitions didn't fit anywhere nicely, so create a new file to
> house various xtheadvector instruction encodings.
> 
> Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> ---
>  arch/riscv/include/asm/xtheadvector.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/xtheadvector.h b/arch/riscv/include/asm/xtheadvector.h
> new file mode 100644
> index 000000000000..348263ea164c
> --- /dev/null
> +++ b/arch/riscv/include/asm/xtheadvector.h
> @@ -0,0 +1,25 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +/*
> + * Vector 0.7.1 as used for example on T-Head Xuantie cores, uses an older
> + * encoding for vsetvli (ta, ma vs. d1), so provide an instruction for
> + * vsetvli	t4, x0, e8, m8, d1
> + */
> +#define THEAD_VSETVLI_T4X0E8M8D1	".long	0x00307ed7\n\t"
> +#define THEAD_VSETVLI_X0X0E8M8D1	".long	0x00307057\n\t"
> +
> +/*
> + * While in theory, the vector-0.7.1 vsb.v and vlb.v result in the same
> + * encoding as the standard vse8.v and vle8.v, compilers seem to optimize
> + * the call resulting in a different encoding and then using a value for
> + * the "mop" field that is not part of vector-0.7.1
> + * So encode specific variants for vstate_save and _restore.

This wording seems oddly familiar to me, did Heiko not write this?

> + */
> +#define THEAD_VSB_V_V0T0		".long	0x02028027\n\t"
> +#define THEAD_VSB_V_V8T0		".long	0x02028427\n\t"
> +#define THEAD_VSB_V_V16T0		".long	0x02028827\n\t"
> +#define THEAD_VSB_V_V24T0		".long	0x02028c27\n\t"
> +#define THEAD_VLB_V_V0T0		".long	0x012028007\n\t"
> +#define THEAD_VLB_V_V8T0		".long	0x012028407\n\t"
> +#define THEAD_VLB_V_V16T0		".long	0x012028807\n\t"
> +#define THEAD_VLB_V_V24T0		".long	0x012028c07\n\t"
> 
> -- 
> 2.44.0
> 

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