DP Link Training Fail and Freeze

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
1

Hello,

This is a follow on to the solution I got working in this previous thread: Jetson Nano DisplayPort Force - Bypass EDID

The problem I am seeing is that this solution works very well once it is up and running it is stable once it is up with HBR2/4 lanes. However it only comes up ~1/10 times the DP sink is plugged. What I see happening is that on the hot plug event the DP display is showing up in the System Settings control panel with the correct resolution, however the whole UI becomes very laggy and unresponsive until I unplug the display and then it reverts to normal. About 1/10 times it does not show this problem and the UI works fine, DP display works fine, etc. I have verified that this does not follow any particular display or cable. I have tried multiple DP sinks and multiple DP cables and the issue is the same so I do not believe it is an SI issue or an issue with the panel itself.

Looking deeper on the issue in the kernel logs, I can see when this happens that the DP link training is not completing for some reason. In fact, the link training doesn’t even get past the CR stage. Again, in the normal case, the link training completes successfully and the sink trains to the full HBR2 rate with 4 lanes at the lowest VOD settings so it seems that the SI quality is good.

Here is the log of what is happening in the failing case. Can you help me diagnose specifically what is happening here and how to fix it? I’m thinking it has something to do with the timing of the AUX transactions in relation to the hot plug event since the EDID bypass is enabled so the link training should be theoretically starting earlier than normal? It is strange to me that 1/10 times it actually trains without any issue and can work error free.

[ 158.728561] hpd: Display connected, hpd_switch 1
[ 158.728565] hpd: switching from state 2 (Check EDID) to state 4 (Enabled)
[ 158.761437] dp lt: state 5 (link training pass), pending_lt_evt 1
[ 158.761441] dp lt: switching from state 5 (link training pass) to state 0 (Reset)
[ 158.761444] dp lt: state 0 (Reset), pending_lt_evt 0
[ 158.761449] dp lt: link training force disable
[ 158.761451] dp lt: switching from state 0 (Reset) to state 4 (link training fail/disable)
[ 158.837578] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10600000 did not specify bpp
[ 158.837610] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837636] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837660] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837684] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837707] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837730] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837754] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837780] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837804] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837827] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837850] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837876] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837899] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837922] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837946] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.837971] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.837995] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.838019] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.838043] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.838067] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.838091] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.838116] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000080 did not specify bpp
[ 158.838139] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10000000 did not specify bpp
[ 158.840914] tegradc tegradc.0: unblank
[ 158.840926] tegradc tegradc.1: blank - powerdown
[ 158.955104] tegradc tegradc.0: unblank
[ 158.955117] tegradc tegradc.1: blank - powerdown
[ 159.005250] tegradc tegradc.0: unblank
[ 159.005269] tegradc tegradc.1: blank - powerdown
[ 159.005290] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10600000 did not specify bpp
[ 159.005307] tegradc tegradc.1: unblank
[ 159.039990] tegradc tegradc.1: nominal-pclk:148500000 parent:148500000 div:1.0 pclk:148500000 147015000~161865000
[ 159.042033] tegradc tegradc.1: tegra_dp_get_bpp: vmode=0x10600000 did not specify bpp
[ 159.045659] tegradc tegradc.1: DP: no prod_c_hbr2 prod settings node in device tree
[ 159.050240] dp lt: state 4 (link training fail/disable), pending_lt_evt 1
[ 159.050243] dp lt: switching from state 4 (link training fail/disable) to state 0 (Reset)
[ 159.050245] dp lt: state 0 (Reset), pending_lt_evt 0
[ 159.051398] tegradc tegradc.1: DP: no prod_c_hbr2 prod settings node in device tree
[ 159.051559] dp lt: switching from state 0 (Reset) to state 2 (clock recovery)
[ 159.051565] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.051811] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.051824] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.051838] dp lt: config: lane 2: vs level: 0, pe level: 0, pc2 level: 0
[ 159.051851] dp lt: config: lane 3: vs level: 0, pe level: 0, pc2 level: 0
[ 159.051858] dp lt: tx_pu: 0x20
[ 159.053208] dp lt: CR not done
[ 159.053883] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.053885] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.053888] dp lt: new config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.053890] dp lt: new config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.053892] dp lt: CR retry
[ 159.053895] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.053899] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.053915] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.053928] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.053941] dp lt: config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.053954] dp lt: config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.053960] dp lt: tx_pu: 0x30
[ 159.055312] dp lt: CR not done
[ 159.055982] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.055984] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.055986] dp lt: new config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.055988] dp lt: new config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.055989] dp lt: CR retry
[ 159.055992] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.055995] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.056011] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.056025] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.056038] dp lt: config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.056051] dp lt: config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.056056] dp lt: tx_pu: 0x40
[ 159.057404] dp lt: CR not done
[ 159.058078] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.058081] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.058083] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.058085] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.058086] dp lt: CR retry
[ 159.058089] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.058093] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.058110] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.058123] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.058137] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.058151] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.058156] dp lt: tx_pu: 0x60
[ 159.059507] dp lt: CR not done
[ 159.060174] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.060176] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.060177] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.060179] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.060180] dp lt: CR retry
[ 159.060183] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.060186] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.060202] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.060214] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.060227] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.060240] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.060245] dp lt: tx_pu: 0x60
[ 159.061603] dp lt: CR not done
[ 159.062276] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.062279] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.062281] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.062283] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.062285] dp lt: CR retry
[ 159.062287] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.062291] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.062307] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.062321] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.062335] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.062348] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.062354] dp lt: tx_pu: 0x60
[ 159.063702] dp lt: CR not done
[ 159.064369] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.064371] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.064374] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.064376] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.064377] dp lt: CR retry
[ 159.064381] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.064385] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.064402] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.064416] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.064430] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.064444] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.064450] dp lt: tx_pu: 0x60
[ 159.065799] dp lt: CR not done
[ 159.066472] dp lt: new config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.066475] dp lt: new config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.066477] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.066479] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.066481] dp lt: CR adj retry limit 5 reached
[ 159.066484] dp lt: switching from state 2 (clock recovery) to state 6 (reduce link rate)
[ 159.066488] dp lt: state 6 (reduce link rate), pending_lt_evt 0
[ 159.067925] tegradc tegradc.1: DP: no prod_c_hbr prod settings node in device tree
[ 159.067953] dp lt: retry CR, lanes: 4, link rate: 0xa
[ 159.067956] dp lt: switching from state 6 (reduce link rate) to state 2 (clock recovery)
[ 159.067961] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.068216] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.068230] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.068243] dp lt: config: lane 2: vs level: 0, pe level: 0, pc2 level: 0
[ 159.068256] dp lt: config: lane 3: vs level: 0, pe level: 0, pc2 level: 0
[ 159.068262] dp lt: tx_pu: 0x20
[ 159.069635] dp lt: CR not done
[ 159.070316] dp lt: new config: lane 0: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070318] dp lt: new config: lane 1: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070321] dp lt: new config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070323] dp lt: new config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070325] dp lt: CR retry
[ 159.070328] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.070333] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.070350] dp lt: config: lane 0: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070363] dp lt: config: lane 1: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070376] dp lt: config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070389] dp lt: config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.070395] dp lt: tx_pu: 0x30
[ 159.071759] dp lt: CR not done
[ 159.072434] dp lt: new config: lane 0: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072436] dp lt: new config: lane 1: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072438] dp lt: new config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072441] dp lt: new config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072442] dp lt: CR retry
[ 159.072445] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.072449] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.072465] dp lt: config: lane 0: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072478] dp lt: config: lane 1: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072491] dp lt: config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072505] dp lt: config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.072510] dp lt: tx_pu: 0x40
[ 159.073875] dp lt: CR not done
[ 159.074555] dp lt: new config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074558] dp lt: new config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074560] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074562] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074564] dp lt: CR retry
[ 159.074566] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.074570] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.074586] dp lt: config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074599] dp lt: config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074612] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074626] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.074631] dp lt: tx_pu: 0x60
[ 159.076032] dp lt: CR not done
[ 159.076712] dp lt: new config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.076715] dp lt: new config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.076717] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.076720] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.076721] dp lt: max vs reached
[ 159.076724] dp lt: switching from state 2 (clock recovery) to state 6 (reduce link rate)
[ 159.076729] dp lt: state 6 (reduce link rate), pending_lt_evt 0
[ 159.078162] tegradc tegradc.1: DP: no prod_c_rbr prod settings node in device tree
[ 159.078191] dp lt: retry CR, lanes: 4, link rate: 0x6
[ 159.078194] dp lt: switching from state 6 (reduce link rate) to state 2 (clock recovery)
[ 159.078198] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.078442] dp lt: config: lane 0: vs level: 0, pe level: 0, pc2 level: 0
[ 159.078455] dp lt: config: lane 1: vs level: 0, pe level: 0, pc2 level: 0
[ 159.078469] dp lt: config: lane 2: vs level: 0, pe level: 0, pc2 level: 0
[ 159.078482] dp lt: config: lane 3: vs level: 0, pe level: 0, pc2 level: 0
[ 159.078488] dp lt: tx_pu: 0x20
[ 159.079859] dp lt: CR not done
[ 159.080543] dp lt: new config: lane 0: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080546] dp lt: new config: lane 1: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080548] dp lt: new config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080551] dp lt: new config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080552] dp lt: CR retry
[ 159.080555] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.080560] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.080578] dp lt: config: lane 0: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080592] dp lt: config: lane 1: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080606] dp lt: config: lane 2: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080620] dp lt: config: lane 3: vs level: 1, pe level: 0, pc2 level: 0
[ 159.080626] dp lt: tx_pu: 0x30
[ 159.082001] dp lt: CR not done
[ 159.082688] dp lt: new config: lane 0: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082690] dp lt: new config: lane 1: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082693] dp lt: new config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082695] dp lt: new config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082697] dp lt: CR retry
[ 159.082700] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.082704] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.082722] dp lt: config: lane 0: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082736] dp lt: config: lane 1: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082751] dp lt: config: lane 2: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082765] dp lt: config: lane 3: vs level: 2, pe level: 0, pc2 level: 0
[ 159.082771] dp lt: tx_pu: 0x40
[ 159.084415] dp lt: CR not done
[ 159.085149] dp lt: new config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085151] dp lt: new config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085154] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085156] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085157] dp lt: CR retry
[ 159.085161] dp lt: switching from state 2 (clock recovery) to state 2 (clock recovery)
[ 159.085165] dp lt: state 2 (clock recovery), pending_lt_evt 0
[ 159.085183] dp lt: config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085196] dp lt: config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085208] dp lt: config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085220] dp lt: config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.085225] dp lt: tx_pu: 0x60
[ 159.086590] dp lt: CR not done
[ 159.087280] dp lt: new config: lane 0: vs level: 3, pe level: 0, pc2 level: 0
[ 159.087282] dp lt: new config: lane 1: vs level: 3, pe level: 0, pc2 level: 0
[ 159.087285] dp lt: new config: lane 2: vs level: 3, pe level: 0, pc2 level: 0
[ 159.087287] dp lt: new config: lane 3: vs level: 3, pe level: 0, pc2 level: 0
[ 159.087289] dp lt: max vs reached
[ 159.088724] tegradc tegradc.1: DP: no prod_c_rbr prod settings node in device tree
[ 159.088755] dp lt: switching from state 2 (clock recovery) to state 4 (link training fail/disable)
[ 159.088770] dp lt: state 4 (link training fail/disable), pending_lt_evt 0
[ 159.088773] dp lt: NULL state handler in state 4
[ 159.105915] tegradc tegradc.1: unblank

3

Hi,

I think what I should ask first is

  1. Is this nvidia devkit or your custom board?

  2. Which software release is that?

  3. Why do you have to force edid?

  4. The link training fails but you can still see UI on the screen?

4

Hello Wayne,

  1. This is the Nvidia devkit
  2. Jetpack 4.3-b134
  3. This was covered in our previous thread which I linked. Basically I am interfacing with a DP sink which does not support EDID. In the case where the linkup starts correctly it is working well with the EDID bypass. It is just this intermittent linkup which is causing problems. This issue is happening with all DP sinks though since the EDID bypass was implemented, not just the one which doesn’t support EDID
  4. I am plugging two sinks into the Jetson for debugging. HDMI is sent to PC monitor so I can interface with the Jetson and see the UI. The DP port is plugged into the DUT. When the DP source is plugged/unplugged I can see the screen recognized in the UI on the HDMI monitor

Thanks,
Casey
4.

5

Hi,

  1. Please move to jetpack4.5 and see if this issue is still.

  2. Please provide us the edid you are using. If that is your case, it sounds we can reproduce this issue locally too.

6

Hello Wayne,

I’ll see about migrating to Jetpack 4.5 but it may take some time to do that on my end. Actually you can reproduce this issue with the default fallback EDID in the edid.c file too so I don’t think it’s related to the EDID. Would you be able to try it out and see if you see the same issue? Basically apply the fallback edid in edid.c and comment out the edid error check in dp.c and you would have the same setup as me. Those are the only changes I made to the kernel

Best Regards,
Casey

9

Hi,

We cannot reproduce such error after enabling the fallback edid. Every time we reboot, there is link training pass and no sluggish over desktop.

10

Hello Wayne,

Are you testing this specifically on the DP port? I only see the issue on the DP port and not the HDMI port. What changes exactly did you make to enable the fallback EDID in your setup? Can you provide me some detail on your process?

Thanks,
Casey

11

I followed your step here to enable the default edid in our driver.
The only difference is I didn’t remove edid error check. I just notice this one now. Why did you remove edid error check here? Which line is that one you reomved?

12

Hello Wayne,

In my previous thread with you I noted that without bypassing the edid error check in the DP.c driver, then the DP.c will filter out all the custom modes from the fallback EDID and will only ever enable 640x480. I had to comment out the following lines in the dp.c file to get all the intended modes to show up:

if (dc->edid->errors) {
return (mode->xres == 640 && mode->yres == 480)
? true : false;
}

Best Regards,
Casey

13

I am not sure why you have to do that. Are you saying that even you enable the “default edid” provided by us, you still only have 640x480 mode?

14

Wayne,

I went into a lot of detail on this in our previous thread which I linked in our first post. If you just enable fallback edid in the edid.c file, then the fallback edid works properly for the HDMI interface, but for the DP interface it would only ever show 640x480. After much investigation, I found that the reason is that there is an additional function in the dp.c file which checks if the EDID has errors (it appears that it is not referencing the fallback EDID, but is instead looking for the sink EDID which in this case is not there). So I had to comment out the lines above and then after I did that it works properly for the DP port as well (except for the 9/10 times the DP port doesn’t link train properly which causes the system to freeze up). When it link trains properly 1/10 times, then all the supported mode from the fallback EDID show up and I am able to pass the display output onto the panel without issue.

Best Regards,
Casey

17

but for the DP interface it would only ever show 640x480. After much investigation, I found that the reason is that there is an additional function in the dp.c file which checks if the EDID has errors (it appears that it is not referencing the fallback EDID, but is instead looking for the sink EDID which in this case is not there)

I think you need to understand that this “fallback edid” is not a official solution. This is just a debug method when someone is bringing up their carrier boards.

We don’t guarantee that “no edid” case or “removing something from our driver” would definitely work.
For your case, please also try different EDID and see if the issue is still there.