On Thu, 2018-01-04 at 23:46 +0000, Pandiyan, Dhinakaran wrote: > On Thu, 2018-01-04 at 18:21 -0500, Lyude Paul wrote: > > Sorry for the late reply, I've been having very similar issues on my own MST hub > > and I wanted to make sure that they were the same issue, although it seems like > > they aren't. > > > > So; I've been doing a lot of MST debugging this week and last and something I've > > discovered needs to be taken into account sometimes with MST hubs is the actual > > state that they're in at the point that the DRM driver detects them. I've > > managed to on multiple occasions, get my hub into a weird state by: > > > > - Plugging in MST displays into the hub > > - Turning on the machine > > - Unplugging MST displays from the hub (while still in the BIOS) > > - Booting into linux > > - Plugging MST displays into the hub > > - Everything times out, the world explodes, the economy collapses, etc. > > > > I think maybe, especially since this should be perfectly valid behavior and not > > break well or poor behaving hubs, we should do a power cycle with the display > > like this when the DP port initially detects an MST hub and before we start > > doing any serious communication with it. Could you see if this fixes your issue > > instead of the patch you've got here? > > > > Well, my reasoning to power cycle after a failure was to not affect hubs > that work. Besides that I also saw an odd cycle of timeouts and late > replies when I did this. > > 1. Detect hub > 2. Toggle power state and send LINK_ADDRESS req. > 3. LINK_ADDRESS req times out. > 4. Toggle power state and send LINK_ADDRESS req. > 5. Get late response for the first (and expired) LINK_ADDRESS req. > 6. Go to step 3 > > It seems like toggling the power states flushes out some message buffers > in the MST hub. > > But, in the retry approach, power cycling resulted in getting the > response for the current LINK_ADDRESS request along with the previous > one that timed out. > > I could not come up with an explanation for all the behavior. So, I > decided to get back to this later. > > > > As well, mind attaching your full dmesg with drm.debug=0x6? > > I don't have the old logs anymore, will try to get something for you. Here you go Setup: Laptop -> ThinkPad dock -> Dell MST monitor -> Dell monitor Hotplugged display to dock[passed] - https://pastebin.com/CemRGsCb Connected boot[failed] - https://pastebin.com/jjXP6HzB > > -DK > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
