Hi, I have a Thinkpad X250 (i7 from Broadwell generation) on Ultradock (that has a DP MST switch) connected to Yamaha RX-V475. At least once per minute the sound stops shortly for less than a second and then continues normally. This is very annoying and basically renders MST audio support useless, but I did not investigate further so far. The graphical output does _not_ have this problem and continues working normally. The Yamaha av-receiver has a small segment display, which changes it text, but it changes back too fast for me to read. I guess it notices, that the audio stream broke up. I don't see anything useful in dmesg (this is without any special debug flags in kernel parameters). -- Sebastian
(In reply to Sebastian Reichel from comment #0) > Hi, > > I have a Thinkpad X250 (i7 from Broadwell generation) on Ultradock (that has > a DP MST switch) connected to Yamaha RX-V475. At least once per minute the > sound stops shortly for less than a second and then continues normally. This > is very annoying and basically renders MST audio support useless, but I did > not investigate further so far. The graphical output does _not_ have this > problem and continues working normally. The Yamaha av-receiver has a small > segment display, which changes it text, but it changes back too fast for me > to read. I guess it notices, that the audio stream broke up. I don't see > anything useful in dmesg (this is without any special debug flags in kernel > parameters). > > -- Sebastian Hello Sebastian, could you please add the following parameter in the grub: "drm.debug=0xe", and after that get the dmesg and kern.log and attach them. Thanks.
Created attachment 131872 [details] dmesg with "debug=0xe" I played music @ 05:35 for ~2 minutes and had some stuttering. There were no corresponding dmesg debug outputs to the audio interruptions.
Thanks for adding the file. Could you tell me if your MST switcher has an additional power source, an AC/DC adapter or power cord for electrical outlet? This could be affecting the multiplexing process.
The MST Switcher is a Thinkpad Ultradock [0], which supplies power to the notebook. So it has access to a 20V power source. Since it has USB ports, it also has access to 5V. [0] http://www3.lenovo.com/us/en/accessories/docking/mechanical-docks/ThinkPad-Ultra-Dock-90-W/p/40A20090US
Hello Sebastian, It seems that most supported features for MST devices were added for kernel 4.12. Could you please change from 4.11 to 4.12 and try to reproduce the issue again: https://www.kernel.org/ If the issue persist, please get another dmesg and attach it. Also, once you provide more information, please change the tag from "NEEDINFO" to "REOPEN". Thank you.
This is not reproducible in 4.12-rc7.
(In reply to Sebastian Reichel from comment #6) > This is not reproducible in 4.12-rc7. Hello Sebastian, Thanks for the answer. I'm changing to CLOSED since it seems to be fixed.
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