Hi Karol, On Fri, Sep 27, 2019 at 11:53:48PM +0200, Karol Herbst wrote: > > What exactly is the serious issue? I guess it's that the rescan > > doesn't detect the GPU, which means it's not responding to config > > accesses? Is there any timing component here, e.g., maybe we're > > missing some delay like the ones Mika is adding to the reset paths? > > When I was checking up on some of the PCI registers of the bridge > controller, the slot detection told me that there is no device > recognized anymore. I don't know which register it was anymore, though > I guess one could read it up in the SoC spec document by Intel. > > My guess is, that the bridge controller fails to detect the GPU being > here or actively threw it of the bus or something. But a normal system > suspend/resume cycle brings the GPU back online (doing a rescan via > sysfs gets the device detected again) Can you elaborate a bit what kind of scenario the issue happens (e.g steps how it reproduces)? It was not 100% clear from the changelog. Also what the result when the failure happens? I see there is a script that does something but unfortunately I'm not fluent in Python so can't extract the steps how the issue can be reproduced ;-) One thing that I'm working on is that Linux PCI subsystem misses certain delays that are needed after D3cold -> D0 transition, otherwise the device and/or link may not be ready before we access it. What you are experiencing sounds similar. I wonder if you could try the following patch and see if it makes any difference? https://patchwork.kernel.org/patch/11106611/
