Messages in this thread | | | Date | Wed, 6 Apr 2022 17:56:50 +0300 | From | Mika Westerberg <> | Subject | Re: Apple Thunderbolt Display chaining |
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Hi,
On Wed, Apr 06, 2022 at 10:51:41AM +0800, Brad Campbell wrote: > Both included in-line. > > This is cold boot with the chain plugged in. I've re-added the dbg to > print the link number, and I've included your path discovery debugs. > Boot with chain plugged in, wait for it to settle, unplug and replug. > First head in the chain fails with : > > [ 65.778129] [drm:radeon_dp_link_train [radeon]] *ERROR* displayport link status failed > [ 65.778158] [drm:radeon_dp_link_train [radeon]] *ERROR* clock recovery failed
Thanks for the logs!
The DP tunnels look pretty much the same except that the Apple EFI CM seems to assign 7 buffers for the AUX RX path first hop whereas we always use 1 buffer. Not sure if that really makes a difference and we could try to use the same number but first, I realized that the PCI resource allocation seems not to work properly.
Can you disable PCIe tunneling (if you use Ubuntu/Fedora or similar there is the "Thunderbolt -> Direct Access" switch that you can turn off) and try again? Please also take 'sudo lspci -vv' for the resulting topology. I suspect this might also affect the other issues (the timeouts) you are seeing. Note this makes the peripherals connected to the monitors unusable too.
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