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HDMI connection causes crash on i.MX6 Solo

Question asked by Allan Matthew on Feb 19, 2015
Latest reply on Jul 17, 2015 by Daniel Schaeffer

On 50% or so of our custom i.MX6 solo boards we're seeing a crash when an HDMI monitor is connected.  The crash occurs once the system is fully booted and the HDMI cable is inserted.  There is no useful information spit out on the console port, and the crash seems to be very low-level as the user LED (tied to a hearbeat trigger) stops flashing.  Additionally, the kernel will halt during boot if an HDMI cable/monitor is connected with no useful output (see attached boot log).

 

Furthermore, i've been able to determine that its not just an HDMI monitor (of which I've tried many different types) being connected which causes the crash.  I can cause the crash simply by pulling the HDMI HPD pin to 5v.

 

Lastly, and hopefully this is the smoking gun: Normally we use a kernel with a bundled initramfs which mounts/loads a squashfs and an aufs overlay rootfs.  The crash does not occur on boards that are known to fail if I use a kernel that does not have a bundled initramfs, even though the version and defconfig are identical (obviously the boot does not complete, but it fails at the init as expected and I get an image on the HDMI).

 

My bundled uImage is ~9MB in size.  The uImage is loaded to 0x12000000, dtb loaded to 0x18000000.  Linux is based on the 3.10.17 GA release, as is the rootfs and initramfs (built in Yocto).

 

So, my questions are:

1.) Why would a bundled initramfs cause this failure? When no HDMI is connected it seems to operate just fine.

2.) Why does this only occur on 50% of our boards?  Boards from the same batches will work or fail, there does not seem to be a common hardware issue.

 

Thanks,

 

-Allan

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