linux-kernel - Re: [PATCH V3 2/2] cpufreq: scmi: Register for limit change notifications

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <64c6a1bc-92f2-4f44-ab10-cbd2473746f3@arm.com>
Date: Thu, 29 Feb 2024 09:59:38 +0000
From: Lukasz Luba <lukasz.luba@....com>
To: Sibi Sankar <quic_sibis@...cinc.com>
Cc: linux-arm-kernel@...ts.infradead.org, pierre.gondois@....com,
 dietmar.eggemann@....com, morten.rasmussen@....com, viresh.kumar@...aro.org,
 rafael@...nel.org, cristian.marussi@....com, sudeep.holla@....com,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 quic_mdtipton@...cinc.com, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH V3 2/2] cpufreq: scmi: Register for limit change
 notifications



On 2/28/24 17:00, Sibi Sankar wrote:
> 
> 
> On 2/28/24 18:54, Lukasz Luba wrote:
>>
>>
>> On 2/27/24 18:16, Sibi Sankar wrote:
>>> Register for limit change notifications if supported and use the 
>>> throttled
>>> frequency from the notification to apply HW pressure.
> 
> Lukasz,
> 
> Thanks for taking time to review the series!
> 
>>>
>>> Signed-off-by: Sibi Sankar <quic_sibis@...cinc.com>
>>> ---
>>>
>>> v3:
>>> * Sanitize range_max received from the notifier. [Pierre]
>>> * Update commit message.
>>>
>>>   drivers/cpufreq/scmi-cpufreq.c | 29 ++++++++++++++++++++++++++++-
>>>   1 file changed, 28 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/cpufreq/scmi-cpufreq.c 
>>> b/drivers/cpufreq/scmi-cpufreq.c
>>> index 76a0ddbd9d24..78b87b72962d 100644
>>> --- a/drivers/cpufreq/scmi-cpufreq.c
>>> +++ b/drivers/cpufreq/scmi-cpufreq.c
>>> @@ -25,9 +25,13 @@ struct scmi_data {
>>>       int domain_id;
>>>       int nr_opp;
>>>       struct device *cpu_dev;
>>> +    struct cpufreq_policy *policy;
>>>       cpumask_var_t opp_shared_cpus;
>>> +    struct notifier_block limit_notify_nb;
>>>   };
>>> +const struct scmi_handle *handle;

I've missed this bit here.

>>> +static struct scmi_device *scmi_dev;
>>>   static struct scmi_protocol_handle *ph;
>>>   static const struct scmi_perf_proto_ops *perf_ops;
>>>   static struct cpufreq_driver scmi_cpufreq_driver;
>>> @@ -151,6 +155,20 @@ static struct freq_attr *scmi_cpufreq_hw_attr[] = {
>>>       NULL,
>>>   };
>>> +static int scmi_limit_notify_cb(struct notifier_block *nb, unsigned 
>>> long event, void *data)
>>> +{
>>> +    struct scmi_data *priv = container_of(nb, struct scmi_data, 
>>> limit_notify_nb);
>>> +    struct scmi_perf_limits_report *limit_notify = data;
>>> +    struct cpufreq_policy *policy = priv->policy;
>>> +
>>> +    policy->max = clamp(limit_notify->range_max_freq/HZ_PER_KHZ, 
>>> policy->cpuinfo.min_freq,
>>> +                policy->cpuinfo.max_freq);
>>
>> Please take the division operation out of this clamp() call, somewhere
>> above. Currently it 'blurs' these stuff, while it's important convertion
>> to khz. You can call it e.g.:
>>
>> limit_freq_khz = limit_notify->range_max_freq / HZ_PER_KHZ;
>>
>> then use in clamp(limit_freq_khz, ...)
> 
> ack
> 
>>
>>> +
>>> +    cpufreq_update_pressure(policy);
>>> +
>>> +    return NOTIFY_OK;
>>> +}
>>> +
>>>   static int scmi_cpufreq_init(struct cpufreq_policy *policy)
>>>   {
>>>       int ret, nr_opp, domain;
>>> @@ -269,6 +287,15 @@ static int scmi_cpufreq_init(struct 
>>> cpufreq_policy *policy)
>>>           }
>>>       }
>>> +    priv->limit_notify_nb.notifier_call = scmi_limit_notify_cb;
>>> +    ret = handle->notify_ops->devm_event_notifier_register(scmi_dev, 
>>> SCMI_PROTOCOL_PERF,
>>> +                            SCMI_EVENT_PERFORMANCE_LIMITS_CHANGED,
>>> +                            &domain,
>>> +                            &priv->limit_notify_nb);
>>> +    if (ret)
>>> +        dev_warn(cpu_dev,
>>> +             "failed to register for limits change notifier for 
>>> domain %d\n", domain);
>>> +
>>>       priv->policy = policy;
>>>       return 0;
>>> @@ -342,8 +369,8 @@ static int scmi_cpufreq_probe(struct scmi_device 
>>> *sdev)
>>>   {
>>>       int ret;
>>>       struct device *dev = &sdev->dev;
>>> -    const struct scmi_handle *handle;
>>
>> It should be a compilation error...
>>
>>> +    scmi_dev = sdev;
>>>       handle = sdev->handle;
>>
>> due to usage here, wasn't it?
> 
> Not really, isn't it getting the first initialization here?
> Are there any compiler options that I need to turn on to
> catch these?

Yes, you're right, my apologies for confusion.
I couldn't apply the series due issues in two patch sets
in your dependency list.

Now when I have been manually applying the changes I spotted it.