linux-kernel - Re: [PATCH v12 3/9] cpufreq: introduce init_boost callback to initialize boost state for pstate drivers

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Message-ID: <6b780c70-91b2-4d1d-9d4a-cbde8d91d8dc@amd.com>
Date: Wed, 19 Jun 2024 12:37:37 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Perry Yuan <perry.yuan@....com>, rafael.j.wysocki@...el.com,
 viresh.kumar@...aro.org, gautham.shenoy@....com
Cc: Xinmei.Huang@....com, Xiaojian.Du@....com, Li.Meng@....com,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 3/9] cpufreq: introduce init_boost callback to
 initialize boost state for pstate drivers

On 6/19/2024 04:16, Perry Yuan wrote:
> Introduce a new init_boost callback in cpufreq to initialize the boost
> state for specific pstate drivers. This initialization is required before
> calling the set_boost interface for each CPU.
> 
> The init_boost callback will set up and synchronize each CPU's current
> boost state before invoking the set_boost function. Without this step,
> the boost state may be inconsistent across CPUs.
> 
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> ---
>   drivers/cpufreq/cpufreq.c | 13 +++++++++++--
>   include/linux/cpufreq.h   |  2 ++
>   2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 1fdabb660231..64c6770e24c8 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1429,8 +1429,17 @@ static int cpufreq_online(unsigned int cpu)
>   			goto out_free_policy;
>   		}
>   
> -		/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
> -		policy->boost_enabled = cpufreq_boost_enabled() && policy_has_boost_freq(policy);
> +		/* init boost state to prepare set_boost callback for each CPU */
> +		if (cpufreq_driver->init_boost) {
> +			ret = cpufreq_driver->init_boost(policy);
> +			if (ret)
> +				pr_debug("%s: %d: boost initialization failed\n", __func__,
> +					__LINE__);
> +				goto out_offline_policy;

You've got a mistake here that you're missing curly braces around the
"if (ret)" block.

So what's going to happen with this code is that no matter if 
init_boost() succeeds then you'll still offline the policy.

> +		} else {
> +			/* Let the per-policy boost flag mirror the cpufreq_driver boost during init */
> +			policy->boost_enabled = cpufreq_boost_enabled() && policy_has_boost_freq(policy);
> +		}
>   
>   		/*
>   		 * The initialization has succeeded and the policy is online.
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 20f7e98ee8af..0698c0292d8f 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -409,6 +409,8 @@ struct cpufreq_driver {
>   	bool		boost_enabled;
>   	int		(*set_boost)(struct cpufreq_policy *policy, int state);
>   
> +	/* initialize boost state to be consistent before calling set_boost */
> +	int		(*init_boost)(struct cpufreq_policy *policy);
>   	/*
>   	 * Set by drivers that want to register with the energy model after the
>   	 * policy is properly initialized, but before the governor is started.