System not booting into OS when HDMI cable is not connected

[antonyabeepraka]

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

[igorpadykov]

Hi Antony

>Since connecting HDMI or USB resolves the system hang issue, we are doubting

>any power related issues. Is our assumption correct ?

I think this is right, one can recheck power supplies, pay attention to

sect.4.2. Avoiding power pifalls (ripples < 5%), sect.4.4. Checking for clock pitfalls

i.MX8M Hardware Developer’s Guide

Recheck power-up sequence and if there are repetitive hard resets, increase time

between resets to allow board power supplies fully discharge.

Regarding software one can try to test with minimal image and then add additional drivers

one by one.

Best regards
igor
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[antonyabeepraka]

Hi Igor,

Thanks for your feedback.

Meanwhile, we applied our custom patches to imx_4.14.98_2.2.0 kernel and created the image.

With this kernel along with our patch system boots successfully always even without HDMI our USB connected.

But the same set of patches gives system hang issues when HDMI or USB not connected in 4.14.78 kernel.

From our debugging on 4.14.78 kernel, when we remove typec_ptn5100 node entries from devicetree we are facing system hang.

Now in 4.14.98 kernel also we are removing typec_ptn5100 node entries from devicetree, but there is no system hang issues.

We need to remove typec as our custom hardware don't have typec support. I guess typec_ptn5100 will do power delivery for typec USB.

Why this causing system hang issue ?

Please provide your feedback.

Thanks,

Antony

[Noel_V]

Anthony

I needed to do a test on the imx8mm EVK , and I'm running into the same issue . ( no HDMI connection - kernel hangs about 1 sec after login prompt is shown on serial line) ,

Are you willing to share how you worked around it , or what caused it ? 

Thanks

Thank You !