linux-kernel - Re: [PATCH] RISC-V: Provide the frequency of mtime via hwprobe

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Message-ID: <3c20c9f15cd7a9fb1f2e88560c1b089ac8032898.camel@icenowy.me>
Date: Wed, 19 Jun 2024 07:51:14 +0800
From: Icenowy Zheng <uwu@...nowy.me>
To: Jessica Clarke <jrtc27@...c27.com>, Yunhui Cui <cuiyunhui@...edance.com>
Cc: Jonathan Corbet <corbet@....net>, Paul Walmsley
 <paul.walmsley@...ive.com>,  Palmer Dabbelt <palmer@...belt.com>, Albert Ou
 <aou@...s.berkeley.edu>, Clément Léger
 <cleger@...osinc.com>, Evan Green <evan@...osinc.com>, Conor Dooley
 <conor.dooley@...rochip.com>, costa.shul@...hat.com, Andy Chiu
 <andy.chiu@...ive.com>, samitolvanen@...gle.com, linux-doc@...r.kernel.org,
  linux-riscv <linux-riscv@...ts.infradead.org>, LKML
 <linux-kernel@...r.kernel.org>, Palmer Dabbelt <palmer@...osinc.com>
Subject: Re: [PATCH] RISC-V: Provide the frequency of mtime via hwprobe

在 2024-06-18星期二的 18:11 +0100，Jessica Clarke写道：
> On 18 Jun 2024, at 12:46, Yunhui Cui <cuiyunhui@...edance.com> wrote:
> > 
> > From: Palmer Dabbelt <palmer@...osinc.com>
> > 
> > A handful of user-visible behavior is based on the frequency of the
> > machine-mode time.
> > 
> > Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
> > Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> 
> I would suggest referring to the user-mode CSR instead, i.e. “time”
> rather than “mtime” throughout in names and descriptions, since
> that’s
> the thing that user-mode software is actually reading from.

Agree. MTIME isn't even a thing defined in RISC-V ISA -- it's part of
the ACLINT timer spec, but before ACLINT gets widely accepted, it's
just some SiFive thing that got copied by many other vendors (and
vendors such as T-Head even provides CLINT w/o MTIME register (well
because these T-Head cores have reference source code available, this
is because of their CPU design uses an external counter fed as TIME
register)).

> 
> Jess
> 
> 
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> linux-riscv@...ts.infradead.org
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