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System not booting into OS when HDMI cable is not connected

Question asked by Antony Abee Prakash on Apr 7, 2020
Latest reply on Apr 9, 2020 by Antony Abee Prakash

We are facing an issue with our customized imx8mq linux BSP of kernel version 4.14.78.

 

The system is not booting into OS when HDMI is not connected to target board.

 

But the board boots into OS at times say 5 out of 10 hard resets.

The board always boots into OS successfully when we connect HDMI or USB devices(mass storage or keyboard/mouse) in the target board.

 

Below is the kernel logs of kernel hang cases. For each boot kernel hangs at different stages as below:

 

Case 1:

[ 3.374674] imx6q-pcie 33c00000.pcie: pcie phy pll is locked.

[ 3.624548] imx6q-pcie 33c00000.pcie: phy link never came up

[ 3.630234] imx6q-pcie 33c00000.pcie: failed to initialize host

[ 3.636167] imx6q-pcie 33c00000.pcie: unable to add pcie port.

[ 3.642812] imx6q-pcie: probe of 33c00000.pcie failed with error -110

[ 3.652571] galcore: clk_get 2d core clock failed, disable 2d/vg!

[ 3.658829] Galcore version 6.2.4.163672

 

Case 2:

[ 3.673656] imx6q-pcie 33c00000.pcie: pcie phy pll is locked.

[ 3.923590] imx6q-pcie 33c00000.pcie: phy link never came up

[ 3.929282] imx6q-pcie 33c00000.pcie: failed to initialize host

[ 3.935215] imx6q-pcie 33c00000.pcie: unable to add pcie port.

 

We are finding the below observations of successful boot when HDMI is not connected to target.

  1. Pcie 1 disabled
      • pcie1 is disabled from devicetree. pcie1 is routed to pcie slot in the carrier board.
      • System always boots into OS successfully.
  2. LVDS or DualDisplay dtb
      • Booting the kernel with LVDS or Dual display dtb file.
      • System always boots into OS successfully.
  3. Typec
      • Our imx8mq custom target bard doesn't have typec interface.
      • Logically we need to remove typec entries as our hardware do not have support for typec. But removing typec node entries from devicetree causing kernel hang issues.We have removed all typec related stuffs and configs. Still the system hang issue persists.
      • Without removing typec node entries from devicetree, the system boots into OS successfully.

 

Why kernel hang not happened when we use lvds or dual display dtb ?

How removing typec entries is related to system hang issues ?

 

Since connecting HDMI or USB resolves the system hang issue, we are doubting any power related issues. Is our assumption correct ?

 

Please provide your inputs on this.

 

Thanks,

Antony

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