We have custom PCIex4 adapters made with Lanes 0~3 mapped to TX2 PEX Lanes 1~4 without knowing PEX lane 1~4 should be mapped to PCIex4 Lanes 3~0.
Is it possible to remap lanes of TX2 PEX, e.g.:
PEX_RX/TX1 of TX2 <-> PCIe Lane 0
PEX_RX/TX2 of TX2 <-> PCIe Lane 1
PEX_RX/TX3 of TX2 <-> PCIe Lane 2
PEX_RX/TX4 of TX2 <-> PCIe Lane 2
Thanks in advance
If you use reverse routing, I think driver should handle this part without further configuration.
@WayneWWW,
Thanks for quick response.
We could not have NVME SSD detected for our adapter. The same NVME SSD has been tested on M.2 to PCIe adapter. We have PEX_CLK0, +3.3V, GND, PEX_WAKE_L, PEX_CLKREQ_L and PEX_RST_L connected to M.2 connector.
We will make another revision of the adapter with
PEX_RX/TX1 of TX2 <-> PCIe Lane 3
PEX_RX/TX2 of TX2 <-> PCIe Lane 2
PEX_RX/TX3 of TX2 <-> PCIe Lane 1
PEX_RX/TX4 of TX2 <-> PCIe Lane 0
to see if it will make difference.
Any update for this issue?
I made new version of PCBs with lanes swapped but still could not have 4 lane or even one lane PCIe M.2 cards listed by “lspci”.
I suspect the issue could be PEX_WAKE_L, PEX_CLKREQ_L and PEX_RST_L or other signals. I noticed Xavier carrier card has 3.3V/1.8V level shifter for PEX_WAKE_L, but TX2 carrier card doesn’t have level shifter.
The same M.2 cards worked on M.2 to PCIe adapter on TX2 Dev kit. I noticed the CLLKREQ (PCIe slot pin B12, RSVD) is unconnected on the working M.2 to PCIe adapter.
I do not have PCIe/M.2 specs and not sure how the three signals (PEX_WAKE_L, PEX_CLKREQ_L and PEX_RST_L) affect PCIe operations.
The other difference is the M.2 to PCIe adapter converts 12VDC to 3.3V for the M.2 card, but our carrier card uses “VDD_3V3_SLP” for M.2 card.
I did try worm reboot but still could not have M.2 card detected by lspci.
It’s finally working with swapping TX/RX lanes.