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Message-ID: <9e5d9733-10da-47c1-b265-07c6ac820ea6@huawei.com>
Date: Thu, 15 Jan 2026 16:20:49 +0800
From: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
To: Sumit Gupta <sumitg@...dia.com>
CC: <rafael@...nel.org>, <viresh.kumar@...aro.org>, <lenb@...nel.org>,
<robert.moore@...el.com>, <corbet@....net>, <pierre.gondois@....com>,
<rdunlap@...radead.org>, <ray.huang@....com>, <gautham.shenoy@....com>,
<mario.limonciello@....com>, <perry.yuan@....com>, <ionela.voinescu@....com>,
<zhanjie9@...ilicon.com>, <linux-pm@...r.kernel.org>,
<linux-acpi@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<acpica-devel@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
<linux-tegra@...r.kernel.org>, <treding@...dia.com>, <jonathanh@...dia.com>,
<vsethi@...dia.com>, <ksitaraman@...dia.com>, <sanjayc@...dia.com>,
<nhartman@...dia.com>, <bbasu@...dia.com>
Subject: Re: [PATCH v5 08/11] cpufreq: CPPC: sync policy limits when updating
min/max_perf
On 2026/1/8 21:53, Sumit Gupta wrote:
>
> On 25/12/25 19:26, zhenglifeng (A) wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> On 2025/12/23 20:13, Sumit Gupta wrote:
>>> When min_perf or max_perf is updated via sysfs in autonomous mode, the
>>> policy frequency limits should also be updated to reflect the new
>>> performance bounds.
>>>
>>> Add @update_policy parameter to cppc_cpufreq_set_mperf_limit() to
>>> control whether policy constraints are synced with HW registers.
>>> The policy is updated only when autonomous selection is enabled to
>>> keep SW limits in sync with HW.
>>>
>>> This ensures that scaling_min_freq and scaling_max_freq values remain
>>> consistent with the actual min/max_perf register values when operating
>>> in autonomous mode.
>>>
>>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>>> ---
>>> drivers/cpufreq/cppc_cpufreq.c | 35 ++++++++++++++++++++++++++--------
>>> 1 file changed, 27 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
>>> index 1f8825006940..0202c7b823e6 100644
>>> --- a/drivers/cpufreq/cppc_cpufreq.c
>>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>>> @@ -544,14 +544,20 @@ static void populate_efficiency_class(void)
>>> * cppc_cpufreq_set_mperf_limit - Set min/max performance limit
>>> * @policy: cpufreq policy
>>> * @val: performance value to set
>>> + * @update_policy: whether to update policy constraints
>>> * @is_min: true for min_perf, false for max_perf
>>> + *
>>> + * When @update_policy is true, updates cpufreq policy frequency limits.
>>> + * @update_policy is false during cpu_init when policy isn't fully set up.
>>> */
>>> static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
>>> - bool is_min)
>>> + bool update_policy, bool is_min)
>>> {
>>> struct cppc_cpudata *cpu_data = policy->driver_data;
>>> struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>>> unsigned int cpu = policy->cpu;
>>> + struct freq_qos_request *req;
>>> + unsigned int freq;
>>> u32 perf;
>>> int ret;
>>>
>>> @@ -571,15 +577,26 @@ static int cppc_cpufreq_set_mperf_limit(struct cpufreq_policy *policy, u64 val,
>>> else
>>> cpu_data->perf_ctrls.max_perf = perf;
>>>
>>> + if (update_policy) {
>>> + freq = cppc_perf_to_khz(caps, perf);
>>> + req = is_min ? policy->min_freq_req : policy->max_freq_req;
>>> +
>>> + ret = freq_qos_update_request(req, freq);
>>> + if (ret < 0) {
>>> + pr_warn("Failed to update %s_freq constraint for CPU%d: %d\n",
>>> + is_min ? "min" : "max", cpu, ret);
>>> + return ret;
>>> + }
>>> + }
>>> +
>> OK. Now I see the necessity of extracting this function. But why not use
>> freq_khz as a input parameter and convert it to perf in this funciton,
>> since you need the freq here?
>
> That will still need cppc_perf_to_khz to be called so that policy
> has what HW actually delivers. Otherwise, there could be some
> asymmetry.
> Also the clamping is done on perf values. So, if user provides a
> very high freq value then that will get passed to freq_qos and the
> HW register will have actual perf value which doesn't match with qos.
>
> Either way the conversion chain is:
> freq_to_perf -> clamp perf -> set perf -> perf_to_freq -> set qos
> It's just a matter of where we place the logic.
Yes, you are right. I missed the clamping. Thanks for the explanation.
>
> Thank you,
> Sumit Gupta
>
>>> return 0;
>>> }
>>>
>>> -#define cppc_cpufreq_set_min_perf(policy, val) \
>>> - cppc_cpufreq_set_mperf_limit(policy, val, true)
>>> -
>>> -#define cppc_cpufreq_set_max_perf(policy, val) \
>>> - cppc_cpufreq_set_mperf_limit(policy, val, false)
>>> +#define cppc_cpufreq_set_min_perf(policy, val, update_policy) \
>>> + cppc_cpufreq_set_mperf_limit(policy, val, update_policy, true)
>>>
>>> +#define cppc_cpufreq_set_max_perf(policy, val, update_policy) \
>>> + cppc_cpufreq_set_mperf_limit(policy, val, update_policy, false)
>>> static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int cpu)
>>> {
>>> struct cppc_cpudata *cpu_data;
>>> @@ -988,7 +1005,8 @@ static ssize_t store_min_perf(struct cpufreq_policy *policy, const char *buf,
>>> perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>>>
>>> guard(mutex)(&cppc_cpufreq_update_autosel_config_lock);
>>> - ret = cppc_cpufreq_set_min_perf(policy, perf);
>>> + ret = cppc_cpufreq_set_min_perf(policy, perf,
>>> + cpu_data->perf_ctrls.auto_sel);
>>> if (ret)
>>> return ret;
>>>
>>> @@ -1045,7 +1063,8 @@ static ssize_t store_max_perf(struct cpufreq_policy *policy, const char *buf,
>>> perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>>>
>>> guard(mutex)(&cppc_cpufreq_update_autosel_config_lock);
>>> - ret = cppc_cpufreq_set_max_perf(policy, perf);
>>> + ret = cppc_cpufreq_set_max_perf(policy, perf,
>>> + cpu_data->perf_ctrls.auto_sel);
>>> if (ret)
>>> return ret;
>>>
>
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