Messages in this thread | | | Subject | Re: [PATCH v4 3/4] scmi-cpufreq: get opp_shared_cpus from opp-v2 for EM | From | Lukasz Luba <> | Date | Tue, 8 Dec 2020 11:34:36 +0000 |
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On 12/8/20 11:20 AM, Sudeep Holla wrote: > On Tue, Dec 08, 2020 at 12:56:11PM +0530, Viresh Kumar wrote: >> On 08-12-20, 07:22, Nicola Mazzucato wrote: >>> On 12/8/20 5:50 AM, Viresh Kumar wrote: >>>> On 02-12-20, 17:23, Nicola Mazzucato wrote: >>>>> nr_opp = dev_pm_opp_get_opp_count(cpu_dev); >>>>> if (nr_opp <= 0) { >>>>> - dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n"); >>>>> - ret = -EPROBE_DEFER; >>>>> - goto out_free_opp; >>>>> + ret = handle->perf_ops->device_opps_add(handle, cpu_dev); >>>>> + if (ret) { >>>>> + dev_warn(cpu_dev, "failed to add opps to the device\n"); >>>>> + goto out_free_cpumask; >>>>> + } >>>>> + >>>>> + ret = dev_pm_opp_set_sharing_cpus(cpu_dev, opp_shared_cpus); >>>>> + if (ret) { >>>>> + dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n", >>>>> + __func__, ret); >>>>> + goto out_free_cpumask; >>>>> + } >>>>> + >>>> >>>> Why do we need to call above two after calling >>>> dev_pm_opp_get_opp_count() ? >>> >>> Sorry, I am not sure to understand your question here. If there are no opps for >>> a device we want to add them to it >> >> Earlier we used to call handle->perf_ops->device_opps_add() and >> dev_pm_opp_set_sharing_cpus() before calling dev_pm_opp_get_opp_count(), why is >> the order changed now ? >> >> >> I am not sure why they would be duplicated in your case. I though >> device_opps_add() is responsible for dynamically adding the OPPs here. >> > > It is because of per-CPU vs per domain drama here. Imagine a system with > 4 CPUs which the firmware puts in individual domains while they all are > in the same perf domain and hence OPP is marked shared in DT. > > Since this probe gets called for all the cpus, we need to skip adding > OPPs for the last 3(add only for 1st one and mark others as shared). > If we attempt to add OPPs on second cpu probe, it *will* shout as duplicate > OPP as we would have already marked it as shared table with the first cpu. > Am I missing anything ? I suggested this as Nicola saw OPP duplicate > warnings when he was hacking up this patch. > >>> otherwise no need as they would be duplicated. >>>> And we don't check the return value of >>>> the below call anymore, moreover we have to call it twice now. > > Yes, that looks wrong, we need to add the check for non zero values, but .... > >>> >>> This second get_opp_count is required such that we register em with the correct >>> opp number after having added them. Without this the opp_count would not be correct. >> > > ... I have a question here. Why do you need to call > > em_dev_register_perf_domain(cpu_dev, nr_opp, &em_cb, opp_shared_cpus..) > > on each CPU ? Why can't that be done once for unique opp_shared_cpus ?
It just have to be called once, for one CPU from the mask. Otherwise for the next CPUs you should see error: "EM: exists for CPU%d" It can happen that this print is not seen when the get_cpu_device(cpu) failed, but that would lead to investigation why CPU devices are not there yet.
Nicola: have you seen that print?
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