Chen-Yu Tsai <wenst@xxxxxxxxxxxx> writes: > On Fri, May 20, 2022 at 5:53 PM Chanwoo Choi <cw00.choi@xxxxxxxxxxx> wrote: >> >> Hi Kevin, >> >> On 5/20/22 11:42 AM, Chen-Yu Tsai wrote: >> > On Fri, May 20, 2022 at 9:28 AM Chanwoo Choi <cw00.choi@xxxxxxxxxxx> wrote: >> >> >> >> Hi Kevin, Chen-Yu, >> >> >> >> On 5/20/22 3:25 AM, Kevin Hilman wrote: >> >>> Chen-Yu Tsai <wenst@xxxxxxxxxxxx> writes: >> >>> >> >>>> n Wed, May 18, 2022 at 8:03 AM Kevin Hilman <khilman@xxxxxxxxxx> wrote: >> >>>>> >> >>>>> Kevin Hilman <khilman@xxxxxxxxxx> writes: >> >>>>> >> >>>>>> Chen-Yu Tsai <wenst@xxxxxxxxxxxx> writes: >> >>>>>> >> >>>>>>> On Mon, May 16, 2022 at 8:43 AM Roger Lu <roger.lu@xxxxxxxxxxxx> wrote: >> >>>>>>>> >> >>>>>>>> The Smart Voltage Scaling(SVS) engine is a piece of hardware >> >>>>>>>> which calculates suitable SVS bank voltages to OPP voltage table. >> >>>>>>>> Then, DVFS driver could apply those SVS bank voltages to PMIC/Buck >> >>>>>>>> when receiving OPP_EVENT_ADJUST_VOLTAGE. >> >>>>>>>> >> >>>>>>>> 1. SVS driver uses OPP adjust event in [1] to update OPP table voltage part. >> >>>>>>>> 2. SVS driver gets thermal/GPU device by node [2][3] and CPU device by get_cpu_device(). >> >>>>>>>> After retrieving subsys device, SVS driver calls device_link_add() to make sure probe/suspend callback priority. >> >>>>>>>> >> >>>>>>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git/commit/?h=opp/linux-next&id=25cb20a212a1f989385dfe23230817e69c62bee5 >> >>>>>>>> [2] https://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm.git/commit/?h=opp/linux-next&id=b325ce39785b1408040d90365a6ab1aa36e94f87 >> >>>>>>>> [3] https://git.kernel.org/pub/scm/linux/kernel/git/matthias.bgg/linux.git/commit/?h=v5.16-next/dts64&id=a8168cebf1bca1b5269e8a7eb2626fb76814d6e2 >> >>>>>>>> >> >>>>>>>> Change since v24: >> >>>>>>>> - Rebase to Linux 5.18-rc6 >> >>>>>>>> - Show specific fail log in svs_platform_probe() to help catch which step fails quickly >> >>>>>>>> - Remove struct svs_bank member "pd_dev" because all subsys device's power domain has been merged into one node like above [3] >> >>>>>>>> >> >>>>>>>> Test in below environment: >> >>>>>>>> SW: Integration Tree [4] + Thermal patch [5] + SVS v25 (this patchset) >> >>>>>>>> HW: mt8183-Krane >> >>>>>>>> >> >>>>>>>> [4] https://protect2.fireeye.com/v1/url?k=847bae75-e5f0bb43-847a253a-000babff9b5d-0b6f42041b9dea1d&q=1&e=37a26c43-8564-4808-9701-dc76d1ebbb27&u=https%3A%2F%2Fgithub.com%2Fwens%2Flinux%2Fcommits%2Fmt8183-cpufreq-cci-svs-test >> >>>>>>> >> >>>>>>> I've updated my branch to include all the latest versions of the relevant >> >>>>>>> patch series: >> >>>>>>> >> >>>>>>> - anx7625 DPI bus type series v2 (so the display works) >> >>>>>>> - MT8183 thermal series v9 (this seems to have been overlooked by the >> >>>>>>> maintainer) >> >>>>>>> - MTK SVS driver series v25 >> >>>>>>> - devfreq: cpu based scaling support to passive governor series v5 >> >>>>>>> - MTK CCI devfreq series v4 >> >>>>>>> - MT8183 cpufreq series v7 >> >>>>>>> - Additional WIP patches for panfrost MTK devfreq >> >>>>>> >> >>>>>> Thanks for preparing an integration branch Chen-Yu. >> >>>>>> >> >>>>>> I'm testing this on mt8183-pumpkin with one patch to add the CCI >> >>>>>> regulator[1], and the defconfig you posted in a previous rev of this >> >>>>>> series, but the CCI driver still causes a fault on boot[2] on my >> >>>>>> platform. >> >>>>>> >> >>>>>> I mentioned in earlier reviews that I think there's potentially a race >> >>>>>> between CCI and SVS loading since they are co-dependent. My hunch is >> >>>>>> that this is still not being handled properly. >> >>>>> >> >>>>> Ah, actually it's crashing when I try to boot the platform with >> >>>>> `maxcpus=4` on the cmdline (which I have to do because mt8183-pumpkin is >> >>>>> unstable upstream with the 2nd cluster enabled.) >> >> >> >> This warning message is printed by 'WARN_ON(cpufreq_passive_unregister_notifier(devfreq))' >> >> on devfreq passive governor. >> >> >> >> If the cpufreq drivers are not probed before of probing cci devfreq driver >> >> with passive governor, passive governor shows this warning message. >> >> Because passive governor with CPUFREQ_PARENT_DEV depends on the cpufreq driver >> >> in order to get 'struct cpufreq_policy'[2]. >> >> >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/tree/drivers/devfreq/governor_passive.c?h=devfreq-testing#n339 >> >> [2] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/tree/drivers/devfreq/governor_passive.c?h=devfreq-testing#n282 >> >> >> >> But, as I knew, this message might not stop the kernel. Just show the warning >> >> message and then return -EPROBE_DEFER error. It means that maybe try to >> >> probe the cci devfreq driver on late time of kernel booting >> >> and then will be working. But, I need the full kernel booting log >> >> and the booting sequence of between cpufreq and cci devfreq driver. >> > >> > Maybe just use a standard dev_warn() instead? WARN_ON causes all sorts >> > of panicking in developers' minds. :p >> > >> >> In order to fix your issue, could you share the full booting log? >> >> And if possible, please explain the more detailed something about this. >> > >> > The shortened version is that on an 8 core system, with maxcpus=4, >> > only the first four cores are booted and have cpufreq associated. >> > I've not actually used this mechanism, so I don't really know what >> > happens if the other cores are brought up later with hotplug. Is >> > cpufreq expected to attach to them? >> > >> > Maybe Kevin can add some more details. >> > >> > >> > ChenYu >> > >> > >> >>>>> >> >>>>> The CCI driver should be a bit more robust about detecting >> >>>>> available/online CPUs >> >>>> >> >>>> This all seems to be handled in the devfreq passive governor. >> >>> >> >>> Well, that's the initial crash. But the SVS driver will also go through >> >>> its svs_mt8183_banks[] array (including both big & little clusters) and >> >>> try to init SVS, so presumably that will have some problems also if only >> >>> one cluster is enabled. >> >>> >> >>>> And presumably we'd like to have CCI devfreq running even if just one >> >>>> core was booted. >> >>> >> >>> Yes, I assume so also. >> >>> >> >>>> Added Chanwoo for more ideas. >> >>> >> >>> OK, thanks. >> >>> >> >>> Kevin >> >> >> I tested the passive governor with my temporary test code >> on odroid-xu3 which contains the big.LITTLE cluster (Octa-core). >> >> >> [Sequence of cpufreq/devfreq driver] >> 1. Turn on all cpus >> 2. Probed cpufreq driver >> 3. Probed devfreq driver using passive governor with CPUFREQ_PARENT_DEV >> >> In my test case, there are no warning message during kernel booting. >> Also when scaling the cpu frequency of cpus of big.LITTLE clusters, >> temporary devfreq driver receives the notfication and then >> calculate the target frequency of devfreq device by iterating online cpu. >> >> If there are any h/w constraints on your case, please let me know. > > Could you run your system with maxcpus=4 added to your cmdline? > This is what Kevin was running. > > The current result is that the latter four cores aren't booted, so no > cpufreq tied to them, and the passive governor will fail to get their > cpufreq_policy. As mentioned before, the code path used to have a > WARN_ON(). Now it's a dev_warn(). It will still fail initialization > though. > > We're wondering if devfreq passive governor should be made to work > even if not all cpu cores are available when it probes. For info, here is a boot log[1] from mt8183-pumpkin board where I'm testing Chen-Yu's lastest integration branch. As Chen-Yu said, the part that makes it trigger the warn is disabling some of the CPUs *at boot time*. In this case, I'm passing `maxcpus=4` on the kernel command line. Kevin [1] https://termbin.com/zidi
