Buffer credits on unused port

[Daryl Roach]

DCX8510.  How can a port with nothing connected be logging Credit buffer zeros?

porterrshow -i 1
frames enc crc crc too too bad enc disc link loss loss frjt fbsy c3timeout pcs
tx rx in err g_eof shrt long eof out c3 fail sync sig tx rx err
1: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

portstatsshow -i 1
port: 1
=========
stat_wtx 0 4-byte words transmitted
stat_wrx 0 4-byte words received
stat_ftx 0 Frames transmitted
stat_frx 0 Frames received
stat_c2_frx 0 Class 2 frames received
stat_c3_frx 0 Class 3 frames received
stat_lc_rx 0 Link control frames received
stat_mc_rx 0 Multicast frames received
stat_mc_to 0 Multicast timeouts
stat_mc_tx 0 Multicast frames transmitted
tim_rdy_pri 0 Time R_RDY high priority
tim_txcrd_z 66227817 Time TX Credit Zero (2.5Us ticks)
tim_txcrd_z_vc 0- 3: 0 0 0 66227817
tim_txcrd_z_vc 4- 7: 0 0 0 0
tim_txcrd_z_vc 8-11: 0 0 0 0
tim_txcrd_z_vc 12-15: 0 0 0 0
tim_latency_vc 0- 3: 1 1 1 1
tim_latency_vc 4- 7: 1 1 1 1
tim_latency_vc 8-11: 1 1 1 1
tim_latency_vc 12-15: 1 1 1 1
fec_cor_detected 0 Count of blocks that were corrected by FEC
fec_uncor_detected 0 Count of blocks that were left uncorrected by FEC
er_enc_in 0 Encoding errors inside of frames
er_crc 0 Frames with CRC errors
er_trunc 0 Frames shorter than minimum
er_toolong 0 Frames longer than maximum
er_bad_eof 0 Frames with bad end-of-frame
er_enc_out 0 Encoding error outside of frames
er_bad_os 0 Invalid ordered set
er_pcs_blk 0 PCS block errors
er_rx_c3_timeout 0 Class 3 receive frames discarded due to timeout
er_tx_c3_timeout 0 Class 3 transmit frames discarded due to timeout
er_unroutable 0 Frames that are unroutable
er_unreachable 0 Frames with unreachable destination
er_other_discard 0 Other discards
er_type1_miss 0 frames with FTB type 1 miss
er_type2_miss 0 frames with FTB type 2 miss
er_type6_miss 0 frames with FTB type 6 miss
er_zone_miss 0 frames with hard zoning miss
er_lun_zone_miss 0 frames with LUN zoning miss
er_crc_good_eof 0 Crc error with good eof
er_inv_arb 0 Invalid ARB
er_single_credit_loss 0 Single vcrdy/frame loss on link
er_multi_credit_loss 0 Multiple vcrdy/frame loss on link
phy_stats_clear_ts 10-20-2019 EDT Sun 15:25:29 Timestamp of phy_port stats clear
lgc_stats_clear_ts 10-20-2019 EDT Sun 15:25:29 Timestamp of lgc_port stats clear