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>>>       } >>> >>> +     /* >>> +      * Initialize OSPM Nominal Performance to inform firmware of >>> +      * OSPM's nominal level. Performance above this value = boost; >>> +      * below = throttle. Uses platform nominal by default. >>> +      */ >>> +     ret = cppc_set_ospm_nominal_perf(cpu, caps->nominal_perf); >>> +     if (ret && ret != -EOPNOTSUPP) >>> +             pr_debug("Failed to set ospm_nominal_perf for CPU%d: >>> %d\n", >>> +                      cpu, ret); >>> + >> >> IIUC, if (ospm_nominal_perf == nominal_perf), the firmware should >> not behave differently. Is this really useful ? >> > > Right, it's a no-op from the firmware's side. The init was only so that > sysfs would show a value (platform nominal) before any userspace write. > Will drop it in v3 and return 0 from sysfs until userspace writes a > value. > > >> ------------ >> >> Also this seems like there will need some synchronization >> mechanism to keep-up with the boost state. >> >> If the ospm_nominal_perf is lowered and boost is disabled, >> a freq. update should happen. IMO it looks like this could >> be handled with (another) freq_qos_request. >> >> This new freq_qos_request, if we name it ospm_nominal_freq_req, >> should only be taken into account if boost is disabled. >> Otherwise, if boost is enabled, ospm_nominal_freq_req >> should be ignored. >> > > Agreed, will add the new freq_qos_request in a follow-up patch. > >> ------------ >> >> Also, the function seems to set the ospm_nominal_freq for >> a single CPU when the policy might be common for multiple >> CPUs right ? > > In v3, after dropping the change from cppc_cpufreq_cpu_init, > the problem won't come in this specific instance. > > >> >> The issues this field raises seems similar to the auto_sel >> ones. I.e. : >> >> - concurrency accesses + need for a scratch value >> >> - what should happen when unloading the driver >> >> - the value can be set for single CPUs but we might >> want to have the same value for the whole policy >> >> Maybe a common solution should be found. >> (I m not suggesting anything right now unfortunately). >> > > One way to address this is to move the sysfs from per-CPU acpi_cppc to > a per-policy node under cpufreq (ospm_nominal_perf_freq, kHz). Yes right, would it make sense to also move the "ospm_nominal_perf" to the cpu_data ? > In the sysfs callback, we can convert kHz to perf and write the register > on every CPU in policy->cpus. > Concurrency is already covered by policy->rwsem at the cpufreq layer. > This is similar to how we were handling min/max_perf in earlier version. Yes right. Something I don't really understand is that similarly to auto_sel, the sysfs rwsem protects the state of the cpu_data->auto_sel field, but we don't really have any guarantee that another driver won't modify the firmware state right ? (maybe it's just not worth ?) > Does this approach make sense? Yes right thanks ! > > Thank you, > Sumit Gupta > > .... > >