linux-kernel - Re: [PATCH 3/4] powercap/drivers/dtpm: Add API for dynamic thermal power management

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Message-ID: <6c018f8e-41b9-55bc-4d47-d2104cabfb86@linaro.org>
Date:   Tue, 10 Nov 2020 13:55:47 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     rafael@...nel.org, srinivas.pandruvada@...ux.intel.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        rui.zhang@...el.com, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Arnd Bergmann <arnd@...db.de>,
        "open list:GENERIC INCLUDE/ASM HEADER FILES" 
        <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 3/4] powercap/drivers/dtpm: Add API for dynamic thermal
 power management


Hi Lukasz,

thanks for the review

On 10/11/2020 10:59, Lukasz Luba wrote:

[ ... ]

>> +/* Init section thermal table */
>> +extern struct dtpm_descr *__dtpm_table[];
>> +extern struct dtpm_descr *__dtpm_table_end[];
>> +
>> +#define DTPM_TABLE_ENTRY(name)            \
>> +    static typeof(name) *__dtpm_table_entry_##name    \
>> +    __used __section(__dtpm_table) = &name
> 
> I had to change the section name to string, to pass compilation:
> __used __section("__dtpm_table") = &name
> I don't know if it's my compiler or configuration.

Actually, it is:

commit 33def8498fdde180023444b08e12b72a9efed41d
Author: Joe Perches <joe@...ches.com>
Date:   Wed Oct 21 19:36:07 2020 -0700

    treewide: Convert macro and uses of __section(foo) to __section("foo")

Your change is correct, I've noticed it a few days ago when rebasing the
series.

> I've tried to register this DTPM in scmi-cpufreq.c with macro
> proposed in patch 4/4 commit message, but I might missed some
> important includes there...
> 
>> +
>> +#define DTPM_DECLARE(name)    DTPM_TABLE_ENTRY(name)
>> +
>> +#define for_each_dtpm_table(__dtpm)    \
>> +    for (__dtpm = __dtpm_table;    \
>> +         __dtpm < __dtpm_table_end;    \
>> +         __dtpm++)
>> +
>> +static inline struct dtpm *to_dtpm(struct powercap_zone *zone)
>> +{
>> +    return container_of(zone, struct dtpm, zone);
>> +}
>> +
>> +int dtpm_update_power(struct dtpm *dtpm, u64 power_min, u64 power_max);
>> +
>> +int dtpm_release_zone(struct powercap_zone *pcz);
>> +
>> +struct dtpm *dtpm_alloc(void);
>> +
>> +void dtpm_unregister(struct dtpm *dtpm);
>> +
>> +int dtpm_register_parent(const char *name, struct dtpm *dtpm,
>> +             struct dtpm *parent);
>> +
>> +int dtpm_register(const char *name, struct dtpm *dtpm, struct dtpm
>> *parent,
>> +          struct powercap_zone_ops *ops, int nr_constraints,
>> +          struct powercap_zone_constraint_ops *const_ops);
>> +#endif
>>
> 
> Minor comment. This new framework deserves more debug prints, especially
> in registration/unregistration paths. I had to put some, to test it.
> But it can be done later as well, after it gets into mainline.

Ok, I will add some debug traces.

> I have also run different hotplug stress tests to check this tree
> locking. The userspace process constantly reading these values, while
> the last CPU in the cluster was going on/off and node was detaching.
> I haven't seen any problems, but the tree wasn't so deep.
> Everything was calculated properly, no error, null pointers, etc.

Great! thank you very much for this test

> Apart from the spelling minor issues and the long constraint name, LGTM
> 
> Reviewed-by: Lukasz Luba <lukasz.luba@....com>
> Tested-by: Lukasz Luba <lukasz.luba@....com>

Thanks for the review

  -- Daniel


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