linux-kernel - Re: [PATCH v3 2/4] cpufreq: CPPC: Avoid using CPUFREQ

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Message-ID: <e01fef03-65cd-4eb6-be48-974bcd59ae23@hisilicon.com>
Date: Sun, 28 Sep 2025 09:59:02 +0800
From: Jie Zhan <zhanjie9@...ilicon.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Linux PM
	<linux-pm@...r.kernel.org>
CC: Shawn Guo <shawnguo@...nel.org>, Qais Yousef <qyousef@...alina.io>, LKML
	<linux-kernel@...r.kernel.org>, Viresh Kumar <viresh.kumar@...aro.org>,
	Pierre Gondois <pierre.gondois@....com>, Mario Limonciello
	<mario.limonciello@....com>, Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] cpufreq: CPPC: Avoid using CPUFREQ_ETERNAL as
 transition delay



On 9/26/2025 6:19 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> If cppc_get_transition_latency() returns CPUFREQ_ETERNAL to indicate a
> failure to retrieve the transition latency value from the platform
> firmware, the CPPC cpufreq driver will use that value (converted to
> microseconds) as the policy transition delay, but it is way too large
> for any practical use.
> 
> Address this by making the driver use the cpufreq's default
> transition latency value (in microseconds) as the transition delay
> if CPUFREQ_ETERNAL is returned by cppc_get_transition_latency().
> 
> Fixes: d4f3388afd48 ("cpufreq / CPPC: Set platform specific transition_delay_us")
> Cc: 5.19+ <stable@...r.kernel.org> # 5.19
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Reviewed-by: Mario Limonciello (AMD) <superm1@...nel.org>
Reviewed-by: Jie Zhan <zhanjie9@...ilicon.com>
> ---
> 
> v1 -> v3:
>    * Change the name of the new function (Jie Zhan)
>    * Add a tag from Mario Limonciello
> 
> ---
>  drivers/cpufreq/cppc_cpufreq.c |   14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)