Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting for once, to make this easily accessible to everyone. As Linus will likely release 6.4 on this or the following Sunday a quick status inquiry so I can brief him appropriately: is there any hope the regression this patch tried to fix will be resolved any time soon? Doesn't look like it from below message and this thread, but maybe I missed something. Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) -- Everything you wanna know about Linux kernel regression tracking: https://linux-regtracking.leemhuis.info/about/#tldr If I did something stupid, please tell me, as explained on that page. #regzbot poke On 20.06.23 17:59, Bjorn Andersson wrote: > On Wed, Jun 14, 2023 at 12:44:15PM -0700, Doug Anderson wrote: >> Hi, >> >> On Wed, Jun 14, 2023 at 11:47 AM Krzysztof Kozlowski >> <krzysztof.kozlowski@xxxxxxxxxx> wrote: >>> >>> On 14/06/2023 20:18, Linux regression tracking (Thorsten Leemhuis) wrote: >>>> On 02.06.23 18:12, Amit Pundir wrote: >>>>> Move lvs1 and lvs2 regulator nodes up in the rpmh-regulators >>>>> list to workaround a boot regression uncovered by the upstream >>>>> commit ad44ac082fdf ("regulator: qcom-rpmh: Revert "regulator: >>>>> qcom-rpmh: Use PROBE_FORCE_SYNCHRONOUS""). >>>>> >>>>> Without this fix DB845c fail to boot at times because one of the >>>>> lvs1 or lvs2 regulators fail to turn ON in time. >>>> >>>> /me waves friendly >>>> >>>> FWIW, as it's not obvious: this... >>>> >>>>> Link: https://lore.kernel.org/all/CAMi1Hd1avQDcDQf137m2auz2znov4XL8YGrLZsw5edb-NtRJRw@xxxxxxxxxxxxxx/ >>>> >>>> ...is a report about a regression. One that we could still solve before >>>> 6.4 is out. One I'll likely will point Linus to, unless a fix comes into >>>> sight. >>>> >>>> When I noticed the reluctant replies to this patch I earlier today asked >>>> in the thread with the report what the plan forward was: >>>> https://lore.kernel.org/all/CAD%3DFV%3DV-h4EUKHCM9UivsFHRsJPY5sAiwXV3a1hUX9DUMkkxdg@xxxxxxxxxxxxxx/ >>>> >>>> Dough there replied: >>>> >>>> ``` >>>> Of the two proposals made (the revert vs. the reordering of the dts), >>>> the reordering of the dts seems better. It only affects the one buggy >>>> board (rather than preventing us to move to async probe for everyone) >>>> and it also has a chance of actually fixing something (changing the >>>> order that regulators probe in rpmh-regulator might legitimately work >>>> around the problem). That being said, just like the revert the dts >>>> reordering is still just papering over the problem and is fragile / >>>> not guaranteed to work forever. >>>> ``` >>>> >>>> Papering over obviously is not good, but has anyone a better idea to fix >>>> this? Or is "not fixing" for some reason an viable option here? >>>> >>> >>> I understand there is a regression, although kernel is not mainline >>> (hash df7443a96851 is unknown) and the only solutions were papering the >>> problem. Reverting commit is a temporary workaround. Moving nodes in DTS >>> is not acceptable because it hides actual problem and only solves this >>> one particular observed problem, while actual issue is still there. It >>> would be nice to be able to reproduce it on real mainline with normal >>> operating system (not AOSP) - with ramdiks/without/whatever. So far no >>> one did it, right? >> >> The worry I have about the revert here is that it will never be able >> to be undone and that doesn't seem great long term. I'm all for a >> temporary revert to fix a problem while the root cause is understood, >> but in this case I have a hard time believing that we'll make more >> progress towards a root cause once the revert lands. All the >> investigation we've done so far seems to indicate that the revert only >> fixes the problem by luck... >> >> I completely agree that moving the nodes in the DTS is a hack and just >> hides the problem. However, it also at least limits the workaround to >> the one board showing the problem and doesn't mean we're stuck with >> synchronous probe for rpmh-regulator for all eternity because nobody >> can understand this timing issue on db845c. >> > > I agree that we shouldn't hide this by reverting the regulator change. > > > And as has been stated a few times already, the symptom indicates that > we have a misconfigured system. > > Before accepting a patch just shuffling the bricks, I'd like to see some > more analysis of what happens wrt the rpmh right before the timeout. > Perhaps the landing team can assist here? > > Regards, > Bjorn > >
