On 29/04/2020 13:35, Dmitry Osipenko wrote: > 29.04.2020 11:55, Thierry Reding пишет: > ... >>>> 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. > > That's the exactly expected behaviour of the RPM force suspend/resume. > The only unexpected part for me is that the tegra_i2c_xfer() runtime > resume then fails in the NOIRQ phase. >From reading the changelog for commit 1e2ef05bb8cf ("PM: Limit race conditions between runtime PM and system sleep (v2))", this is the expected behaviour for runtime resume in the noirq phase. Jon -- nvpublic
