Messages in this thread | | | Subject | Re: [PATCH v3 1/5] powercap/drivers/dtpm: Encapsulate even more the code | From | Lukasz Luba <> | Date | Fri, 12 Mar 2021 10:22:30 +0000 |
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On 3/12/21 10:11 AM, Lukasz Luba wrote: > > > On 3/11/21 10:57 AM, Daniel Lezcano wrote: >> On 11/03/2021 11:15, Lukasz Luba wrote: >>> Hi Daniel, >>> >>> On 3/10/21 11:02 AM, Daniel Lezcano wrote: >>>> In order to increase the self-encapsulation of the dtpm generic code, >>>> the following changes are adding a power update ops to the dtpm >>>> ops. That allows the generic code to call directly the dtpm backend >>>> function to update the power values. >>>> >>>> The power update function does compute the power characteristics when >>>> the function is invoked. In the case of the CPUs, the power >>>> consumption depends on the number of online CPUs. The online CPUs mask >>>> is not up to date at CPUHP_AP_ONLINE_DYN state in the tear down >>>> callback. That is the reason why the online / offline are at separate >>>> state. As there is already an existing state for DTPM, this one is >>>> only moved to the DEAD state, so there is no addition of new state >>>> with these changes. The dtpm node is not removed when the cpu is >>>> unplugged. >>>> >>>> That simplifies the code for the next changes and results in a more >>>> self-encapsulated code. >>>> >>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> >>>> --- >>>> V2: >>>> - Updated the changelog with the CPU node not being removed >>>> - Commented the cpu hotplug callbacks to explain why there are two >>>> callbacks >>>> - Changed 'upt_power_uw' to 'update_power_uw' >>>> - Removed unused cpumask variable >>>> --- >>>> drivers/powercap/dtpm.c | 54 ++++++------- >>>> drivers/powercap/dtpm_cpu.c | 148 >>>> ++++++++++++++++-------------------- >>>> include/linux/cpuhotplug.h | 2 +- >>>> include/linux/dtpm.h | 3 +- >>>> 4 files changed, 97 insertions(+), 110 deletions(-) >>>> >>> >>> [snip] >>> >>>> @@ -210,27 +175,20 @@ static int cpuhp_dtpm_cpu_online(unsigned int >>>> cpu) >>>> for_each_cpu(cpu, policy->related_cpus) >>>> per_cpu(dtpm_per_cpu, cpu) = dtpm; >>>> - sprintf(name, "cpu%d", dtpm_cpu->cpu); >>>> + sprintf(name, "cpu%d-cpufreq", dtpm_cpu->cpu); >>> >>> We should be safe in normal platforms, since there is less than >>> < 300 cores. although, I would use 2x CPUFREQ_NAME_LEN array. >> >> I'm counting 9999 cores. >> >> We have: >> #define CPUFREQ_NAME_LEN 16 >> >> "cpu-cpufreq\0" counts 12 characters. >> >> There are 4 characters left, 9999 max then, no ? > > Yes, my '< 300' was referring to some server platforms, > which IIRC had 2 sockets, each with 128 cores. I don't > know about future, though. > >> >> The code is designed for cpufreq with the energy model which targets >> ARM64 architecture and AFAICT we are far away of having so many cores on >> our phones. > > True, otherwise with such big number of cores in mobile, we would face > probably more hard to investigate issues, than this simple one ;) > >> >> Except I'm wrong, I would prefer to keep the current CPUFREQ_NAME_LEN to >> not introduce subtle bugs (like stack overflow) if the length is >> increased in cpufreq.h. >> >> What do you think ? > > Agree, please skip my former comment and just take the reviewed tag.
What you could do, though, is to use:
snprintf(name, sizeof(name), "cpu%d-cpufreq", dtpm_cpu->cpu);
just to play safe.
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