linux-kernel - Re: [PATCH v2 1/3] MIPS: CPS: Improve mips_cps_first_online_in

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Message-Id: <b3b3d5f5-e62f-4081-9fb0-a176a91361f2@app.fastmail.com>
Date: Fri, 04 Jul 2025 19:03:04 +0100
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Gregory CLEMENT" <gregory.clement@...tlin.com>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>
Cc: "Vladimir Kondratiev" <vladimir.kondratiev@...ileye.com>,
 Théo Lebrun <theo.lebrun@...tlin.com>,
 "Tawfik Bayouk" <tawfik.bayouk@...ileye.com>,
 "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] MIPS: CPS: Improve mips_cps_first_online_in_cluster()



在2025年7月4日周五 下午4:13，Gregory CLEMENT写道：
> The initial implementation of this function goes through all the CPUs
> in a cluster to determine if the current CPU is the only one
> running. This process occurs every time the function is called.
>
> However, during boot, we already perform this task, so let's take
> advantage of this opportunity to create and fill a CPU bitmask that
> can be easily and efficiently used later.
>
> This requires creating a single CPU bitmask per cluster, which is why
> it's essential to know how many clusters can be utilized. The default
> setting is 4 clusters, but this value can be changed when configuring
> the kernel or even customized for a given SoC family.

Hmm, I think we should avoid this sort of random limitation.

You can actually store per cluster cpumask_var_t into `mips_cps_cluster_bootcfg`,
which is allocated in cps_prepare_cpus(), and generate cpumask just there.

It should be pretty straightforward to handle.

Thanks!

>
> This patch modifies the function to allow providing the first
> available online CPU when one already exists, which is necessary for
> delay CPU calibration optimization.
>
> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
[...]
-- 
- Jiaxun