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Regression: AMD GCN GPUs do not enumerate: "phy link never came up"

Question asked by Clemens Eisserer on Aug 5, 2016
Latest reply on Aug 9, 2016 by Clemens Eisserer



I am currently trying to use AMD GCN ("graphic core next") based garphic cards (various manufactureres, different models) in a LS2085ARDB, by using various PCIe4x/8x -> PCIe16x adapters. While 3 different graphic cards based on this architecture worked using these adapters in different PCs (as well as in the T4240RDB), on the LS2085ARDB the GPU is not enumerated, instead I get the following message in dmesg:


  [    3.735939] layerscape-pcie 3600000.pcie: phy link never came up
  [    3.736716] pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring


Tested were both graphic cards with external supply, as well as low-power versions - so the power provided by the PCIe8x slot shouldn't be an issue.


Interestingly, pre-GCN GPUs based on the r600 architecture (~2008 ~2011) enumerate and after some tweaking work very well (even in PCIe2 mode) - however they have been phased out some while ago and do also not support OpenCL (gpu compute). Nvidia GPUs also enumerate and work, however due to the age of the LTS kernel 4.1.8, the driver lacks PCIe-mode-switch as well as GPU/memory-reclocking required for our workload.


Is there an eletric incompatibility between the PHYs built into LS2085A and AMD GCN GPUs?

Just tested those cards in our T4240RDB - and they worked perfectly there too.


Thank you and best regards, Clemens


Our RCW is:


SoC:  LS2085E (0x87010010)
  Clock Configuration:
         CPU0(A57):1800 MHz  CPU1(A57):1800 MHz  CPU2(A57):1800 MHz
         CPU3(A57):1800 MHz  CPU4(A57):1800 MHz  CPU5(A57):1800 MHz
         CPU6(A57):1800 MHz  CPU7(A57):1800 MHz
         Bus:      600  MHz  DDR:      1866.667 MT/s     DP-DDR:   1600 MT/s
  Reset Configuration Word (RCW):
         00: 48303830 48480048 00000000 00000000
         10: 00000000 00200000 00200000 00000000
         20: 01012980 00002580 00000000 00000000
         30: 00000e0b 00000000 00000000 00000000
         40: 00000000 00000000 00000000 00000000
         50: 00000000 00000000 00000000 00000000
         60: 00000000 00000000 00027000 00000000
         70: 412a0000 00000000 00000000 00000000
  Model: Freescale Layerscape 2085a RDB Board
  Board: LS2085E-RDB, Board Arch: V1, Board version: D, boot from vBank: 0
  FPGA: v1.18
  SERDES1 Reference : Clock1 = 156.25MHz Clock2 = 156.25MHz
  SERDES2 Reference : Clock1 = 100MHz Clock2 = 100MHz