29.04.2020 19:54, Dmitry Osipenko пишет: > 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? > My proposal: 1. Fix PCIe driver by keeping regulator always-ON, propagate it to stable kernels. 2. Make I2C driver usable in NOIRQ phase. 3. Make PCIe driver to handle errors properly. 4. Revert the PCIe driver "fix".
