linux-kernel - Re: [PATCH v4] RISC-V: Provide the frequency of time CSR via hwprobe

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Message-ID: <87jzhtmvqg.fsf@bytedance.com>
Date: Wed, 10 Jul 2024 10:39:35 +0100
From: Punit Agrawal <punit.agrawal@...edance.com>
To: paul.walmsley@...ive.com, palmer@...belt.com
Cc: punit.agrawal@...edance.com,  sunilvl@...tanamicro.com,
  jesse@...osinc.com,  jrtc27@...c27.com,  corbet@....net,
 aou@...s.berkeley.edu,  cleger@...osinc.com,  evan@...osinc.com,
  conor.dooley@...rochip.com,  costa.shul@...hat.com,
  andy.chiu@...ive.com,  samitolvanen@...gle.com,
  linux-doc@...r.kernel.org,  linux-riscv@...ts.infradead.org,
  linux-kernel@...r.kernel.org,  Anup Patel <anup@...infault.org>, Yunhui
 Cui <cuiyunhui@...edance.com>, Palmer Dabbelt <palmer@...osinc.com>
Subject: Re: [PATCH v4] RISC-V: Provide the frequency of time CSR via hwprobe

Hi,

Yunhui Cui <cuiyunhui@...edance.com> writes:

> From: Palmer Dabbelt <palmer@...osinc.com>
>
> The RISC-V architecture makes a real time counter CSR (via RDTIME
> instruction) available for applications in U-mode but there is no
> architected mechanism for an application to discover the frequency
> the counter is running at. Some applications (e.g., DPDK) use the
> time counter for basic performance analysis as well as fine grained
> time-keeping.
>
> Add support to the hwprobe system call to export the time CSR
> frequency to code running in U-mode.
>
> Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> Reviewed-by: Evan Green <evan@...osinc.com>
> Reviewed-by: Anup Patel <anup@...infault.org>
> Acked-by: Punit Agrawal <punit.agrawal@...edance.com>
> ---
>  Documentation/arch/riscv/hwprobe.rst  | 2 ++
>  arch/riscv/include/asm/hwprobe.h      | 2 +-
>  arch/riscv/include/uapi/asm/hwprobe.h | 1 +
>  arch/riscv/kernel/sys_hwprobe.c       | 5 +++++
>  4 files changed, 9 insertions(+), 1 deletion(-)

The commit looks ready to be merged. Will this picked up for the 6.11
release?

Once this is merged, we can send out the DPDK change relying on the
newly added key.

Thanks,
Punit

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