On Wed, Apr 29, 2020 at 10:14:48AM +0200, Thierry Reding wrote: > On Mon, Apr 27, 2020 at 06:18:34PM +0300, Dmitry Osipenko wrote: > > 27.04.2020 18:12, Thierry Reding пишет: > > > On Mon, Apr 27, 2020 at 05:21:30PM +0300, Dmitry Osipenko wrote: > > >> 27.04.2020 14:00, Thierry Reding пишет: > > >>> On Mon, Apr 27, 2020 at 12:52:10PM +0300, Dmitry Osipenko wrote: > > >>>> 27.04.2020 10:48, Thierry Reding пишет: > > >>>> ... > > >>>>>> Maybe but all these other problems appear to have existed for sometime > > >>>>>> now. We need to fix all, but for the moment we need to figure out what's > > >>>>>> best for v5.7. > > >>>>> > > >>>>> To me it doesn't sound like we have a good handle on what exactly is > > >>>>> going on here and we're mostly just poking around. > > >>>>> > > >>>>> And even if things weren't working quite properly before, it sounds to > > >>>>> me like this patch actually made things worse. > > >>>> > > >>>> There is a plenty of time to work on the proper fix now. To me it sounds > > >>>> like you're giving up on fixing the root of the problem, sorry. > > >>> > > >>> We're at -rc3 now and I haven't seen any promising progress in the last > > >>> week. All the while suspend/resume is now broken on at least one board > > >>> and that may end up hiding any other issues that could creep in in the > > >>> meantime. > > >>> > > >>> Furthermore we seem to have a preexisting issue that may very well > > >>> interfere with this patch, so I think the cautious thing is to revert > > >>> for now and then fix the original issue first. We can always come back > > >>> to this once everything is back to normal. > > >>> > > >>> Also, people are now looking at backporting this to v5.6. Unless we > > >>> revert this from v5.7 it may get picked up for backports to other > > >>> kernels and then I have to notify stable kernel maintainers that they > > >>> shouldn't and they have to back things out again. That's going to cause > > >>> a lot of wasted time for a lot of people. > > >>> > > >>> So, sorry, I disagree. I don't think we have "plenty of time". > > >> > > >> There is about a month now before the 5.7 release. It's a bit too early > > >> to start the panic, IMO :) > > > > > > There's no panic. A patch got merged and it broken something, so we > > > revert it and try again. It's very much standard procedure. > > > > > >> Jon already proposed a reasonable simple solution: to keep PCIe > > >> regulators always-ON. In a longer run we may want to have I2C atomic > > >> transfers supported for a late suspend phase. > > > > > > That's not really a solution, though, is it? It's just papering over > > > an issue that this patch introduced or uncovered. I'm much more in > > > favour of fixing problems at the root rather than keep papering over > > > until we loose track of what the actual problems are. > > > > It's not "papering over an issue". The bug can't be fixed properly > > without introducing I2C atomic transfers support for a late suspend > > phase, I don't see any other solutions for now. Stable kernels do not > > support atomic transfers at all, that proper solution won't be backportable. > > Hm... on a hunch I tried something and, lo and behold, it worked. I can > get Cardhu to properly suspend/resume on top of v5.7-rc3 with the > following sequence: > > revert 9f42de8d4ec2 i2c: tegra: Fix suspending in active runtime PM state > apply http://patchwork.ozlabs.org/project/linux-tegra/patch/20191213134417.222720-1-thierry.reding@xxxxxxxxx/ > > I also ran that through our test farm and I don't see any other issues. > At the time I was already skeptical about pm_runtime_force_suspend() and > pm_runtime_force_resume() and while I'm not fully certain why exactly it > doesn't work, the above on top of v5.7-rc3 seems like a good option. > > I'll try to do some digging if I can find out why exactly force suspend > and resume doesn't work. Ah... so it looks like pm_runtime_force_resume() never actually does anything in this case and then disable_depth remains at 1 and the first tegra_i2c_xfer() will then fail to runtime resume the controller. Thierry
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