Hi, On Fri, Jan 31, 2025 at 01:41:27AM +0000, Mohammad Rahimi wrote: > Updates the Connection Manager to disable the Gen 4 Link Recovery > flow before transitioning from a Symmetric Link to an Asymmetric > Link, as specified in recent changes to the USB4 v2 specification. > > According to the "USB4 2.0 ENGINEERING CHANGE NOTICE FORM" > published in September 2024, the rationale for this change is: > > "Since the default value of the Target Asymmetric Link might be > different than Symmetric Link and Gen 4 Link Recovery flow checks > this field to make sure it matched the actual Negotiated Link Width, > we’re removing the condition for a Disconnect in the Gen 4 Link > Recovery flow when Target Asymmetric Link doesn’t match the actual > Link width and adding a Connection Manager note to Disable Gen 4 Link > Recovery flow before doing Asymmetric Transitions." > > Signed-off-by: Mohammad Rahimi <rahimi.mhmmd@xxxxxxxxx> I did some minor modifications and applied to thunderbolt.git/next. Please let me know if I missed something. I tested on Intel reference hardware as well but on those link recovery is already disabled so it pretty much does nothing. Below are the steps that I followed: 1. Boot with "thunderbolt.asym_threshold=10000" so that the driver switches links to asymmetric already upon first DP connect. 2. Connect USB4 v2 hub. 3. Check link and PORT_CS_19: # tblist -v Domain 0 Route 0: 8087:5781 Intel Barlow Host Router Type: Router UUID: c9680000... Generation: USB4 NVM version: 56.81 Domain 0 Route 1: 8087:1234 Intel Barlow HUB Router Type: Router Speed (Rx/Tx): 80/80 Gb/s Authorized: No UUID: e9688780... Generation: USB4 NVM version: 56.81 # tbdump -r 0 -a 1 -vv -N 1 PORT_CS_19 0x00d3 0x0004000e 0b00000000 00000100 00000000 00001110 .... PORT_CS_19 [00:00] 0x0 Downstream Port Reset (DPR) [01:01] 0x1 Request RS-FEC Gen 2 (RS2) [02:02] 0x1 Request RS-FEC Gen 3 (RS3) [03:03] 0x1 USB4 Port is Configured (PC) [04:04] 0x0 USB4 Port is Inter-Domain (PID) [16:16] 0x0 Enable Wake on Connect [17:17] 0x0 Enable Wake on Disconnect [18:18] 0x1 Enable Wake on USB4 Wake [19:19] 0x0 Enable Wake on Inter-Domain [24:24] 0x0 StartAsymmetricFlow [30:30] 0x0 Initiate Gen 4 Link Recovery (ILR) [31:31] 0x0 Enable Gen 4 Link Recovery (ELR) # tbdump -r 1 -a 1 -vv -N 1 PORT_CS_19 0x00d3 0x0004000e 0b00000000 00000100 00000000 00001110 .... PORT_CS_19 [00:00] 0x0 Downstream Port Reset (DPR) [01:01] 0x1 Request RS-FEC Gen 2 (RS2) [02:02] 0x1 Request RS-FEC Gen 3 (RS3) [03:03] 0x1 USB4 Port is Configured (PC) [04:04] 0x0 USB4 Port is Inter-Domain (PID) [16:16] 0x0 Enable Wake on Connect [17:17] 0x0 Enable Wake on Disconnect [18:18] 0x1 Enable Wake on USB4 Wake [19:19] 0x0 Enable Wake on Inter-Domain [24:24] 0x0 StartAsymmetricFlow [30:30] 0x0 Initiate Gen 4 Link Recovery (ILR) [31:31] 0x0 Enable Gen 4 Link Recovery (ELR) 3. Connect monitor to USB4 v2 hub. 4. Check link and PORT_CS_19. # tblist -v Domain 0 Route 0: 8087:5781 Intel Barlow Host Router Type: Router UUID: c9680000... Generation: USB4 NVM version: 56.81 Domain 0 Route 1: 8087:1234 Intel Barlow HUB Router Type: Router Speed (Rx/Tx): 120/40 Gb/s Authorized: No UUID: e9688780... Generation: USB4 NVM version: 56.81 # tbdump -r 0 -a 1 -vv -N 1 PORT_CS_19 0x00d3 0x0004000e 0b00000000 00000100 00000000 00001110 .... PORT_CS_19 [00:00] 0x0 Downstream Port Reset (DPR) [01:01] 0x1 Request RS-FEC Gen 2 (RS2) [02:02] 0x1 Request RS-FEC Gen 3 (RS3) [03:03] 0x1 USB4 Port is Configured (PC) [04:04] 0x0 USB4 Port is Inter-Domain (PID) [16:16] 0x0 Enable Wake on Connect [17:17] 0x0 Enable Wake on Disconnect [18:18] 0x1 Enable Wake on USB4 Wake [19:19] 0x0 Enable Wake on Inter-Domain [24:24] 0x0 StartAsymmetricFlow [30:30] 0x0 Initiate Gen 4 Link Recovery (ILR) [31:31] 0x0 Enable Gen 4 Link Recovery (ELR) # tbdump -r 1 -a 1 -vv -N 1 PORT_CS_19 0x00d3 0x0004000e 0b00000000 00000100 00000000 00001110 .... PORT_CS_19 [00:00] 0x0 Downstream Port Reset (DPR) [01:01] 0x1 Request RS-FEC Gen 2 (RS2) [02:02] 0x1 Request RS-FEC Gen 3 (RS3) [03:03] 0x1 USB4 Port is Configured (PC) [04:04] 0x0 USB4 Port is Inter-Domain (PID) [16:16] 0x0 Enable Wake on Connect [17:17] 0x0 Enable Wake on Disconnect [18:18] 0x1 Enable Wake on USB4 Wake [19:19] 0x0 Enable Wake on Inter-Domain [24:24] 0x0 StartAsymmetricFlow [30:30] 0x0 Initiate Gen 4 Link Recovery (ILR) [31:31] 0x0 Enable Gen 4 Link Recovery (ELR)
