Hi, On Mon, May 30, 2022 at 08:57:34PM +0200, Stefan Hoffmeister wrote: > ********** $ cat /sys/kernel/debug/thunderbolt/0-0/port5/regs > ******************** > # offset relative_offset cap_id vs_cap_id value > 0x0000 0 0x00 0x00 0x9a1f8086 > 0x0001 1 0x00 0x00 0x05080239 > 0x0002 2 0x00 0x00 0x010e0101 > 0x0003 3 0x00 0x00 0x80500010 > 0x0004 4 0x00 0x00 0x4100000d > 0x0005 5 0x00 0x00 0x00004809 > 0x0006 6 0x00 0x00 0x00000000 > 0x0007 7 0x00 0x00 0x00000000 > 0x0008 8 0x00 0x00 0x00000000 > 0x0039 0 0x04 0x00 0xc009048f The bits 31:30 tell that this tunnel is active. > ********** $ cat /sys/kernel/debug/thunderbolt/0-0/port6/regs > ******************** > # offset relative_offset cap_id vs_cap_id value > 0x0000 0 0x00 0x00 0x9a1f8086 > 0x0001 1 0x00 0x00 0x05080239 > 0x0002 2 0x00 0x00 0x010e0101 > 0x0003 3 0x00 0x00 0x80600010 > 0x0004 4 0x00 0x00 0x0100000d > 0x0005 5 0x00 0x00 0x00004809 > 0x0006 6 0x00 0x00 0x00000000 > 0x0007 7 0x00 0x00 0x00000000 > 0x0008 8 0x00 0x00 0x00000000 > 0x0039 0 0x04 0x00 0x0009048f This one is not. > ********** $ cat /sys/kernel/debug/thunderbolt/0-1/port11/regs > ******************** > # offset relative_offset cap_id vs_cap_id value > 0x0000 0 0x00 0x00 0x15ef8086 > 0x0001 1 0x00 0x00 0x0608020a > 0x0002 2 0x00 0x00 0x010e0102 > 0x0003 3 0x00 0x00 0x80b00008 > 0x0004 4 0x00 0x00 0x00800000 > 0x0005 5 0x00 0x00 0x00004809 > 0x0006 6 0x00 0x00 0x00000000 > 0x0007 7 0x00 0x00 0x00000000 > 0x0008 8 0x00 0x00 0x00000000 > 0x000a 0 0x03 0x00 0x00000339 > 0x000b 1 0x03 0x00 0x40110005 > 0x000c 2 0x03 0x00 0x00000000 > 0x000d 3 0x03 0x00 0x00000000 > 0x000e 4 0x03 0x00 0xffffffff > 0x000f 5 0x03 0x00 0x00000000 > 0x0010 6 0x03 0x00 0x000009c4 > 0x0011 7 0x03 0x00 0x00c80002 > 0x0039 0 0x04 0x00 0x0009044f > 0x003a 1 0x04 0x00 0x00004008 > 0x003b 2 0x04 0x00 0x000fff40 > 0x003c 3 0x04 0x00 0x00400005 > 0x003d 4 0x04 0x00 0x00c0a234 This is the "local" capability and it tells that this one supports MST (bit 15). I wonder if this dock has the two DP outputs behind a MST "hub" or so? I've seen such devices out there. This would explain why there is only single DP tunnel active. I don't remember if you already mentioned but have you tried to connect the second monitor to the USB-C downstream ports on that dock? At least for some docks this is where the second DP OUT adapter is routed. If the second DP tunnel gets activated you should also see bits 31:30 of the port6/regs to be set by the connection manager firmware.
