29.04.2020 19:30, Thierry Reding пишет: > On Wed, Apr 29, 2020 at 03:35:26PM +0300, 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. >> >> Anyways, again, today it's wrong to use I2C in the NOIRQ phase becasue >> I2C interrupt is disabled. It's the PCIe driver that should be fixed. > > I don't think so. Everything works perfectly fine if we fix system > suspend/resume not to rely on pm_runtime_force_{suspend,resume}() and > directly call the runtime suspend/resume implementations. It should "work" only in conjunction with my I2C patch, otherwise you'll get a spurious I2C timeout error. And it will "work" only because interrupt is handled manually after the timeout, meaning that yours suspending time will take few hundreds ms more. > So can we please stop deflecting and fix the damn I2C driver. From my > perspective we have two choices: > > 1) do what I suggested above and revert the force suspend/resume patch > and apply the "manual" suspend/resume patch instead > > 2) revert this patch and go back to the drawing board > > I suspect that with 2) we'd end up back where we started and have to do > 1) anyway. > > An alternative that I'd prefer even more would be to do 2) now for v5.7 > and then we do 1) for v5.8 and give this some more soaking time. I2C driver isn't broken, PCIe driver is. IMO. Both yours variants are not going to be a backportable fix for the stable kernels, they won't fix the suspended interrupt problem. What I'm missing?
