Can't get second core of A20 out of reset

[Jonathan Fether]

I'm running Armbian for the SOM204-A20:
"Welcome to ARMBIAN 5.41 user-built Debian GNU/Linux 9 (stretch) 4.14.84-sunxi"

I'm unable to get the second core of the A20 online:

Code Select Expand

# cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 4 (v7l)
BogoMIPS        : 16.42
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 4

Hardware        : Allwinner sun7i (A20) Family
Revision        : 0000
Serial          : 165166d502416a4f
terminal++@olimex:/opt
#

This is backed up by checking the CPU reset registers. The second one is being held in reset (Register 0x01C25C80 (CPU1_RST_CTRL)), per the A20 user manual section 1.4.2:

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# devmem2 0x01C25C40
Value at address 0x01C25C40: 0x00000003
terminal++@olimex:/opt
# devmem2 0x01C25C80
Value at address 0x01C25C80: 0x00000000
terminal++@olimex:/opt
#


Do I just have a problem with my install? I'd appreciate any pointers as to what might be causing this.

Best Regards,
Jon Fether

[LubOlimex]

Can you also test with our Armbian-based stretch image from here: ftp://staging.olimex.com/Allwinner_Images/A20-OLinuXino/1.latest_mainline_images/stretch/images/ ? Are the results the same?

[Jonathan Fether]

I took a look at the kernel debs in there. They broke my device tree overlays (Missing /__symbols__ node, DT not compiled with dtc -@). But this wasn't what was requested.

I consulted with some colleagues and they have not encountered the same issue using 4.14.40-sunxi on other A20-SOM204 boards. I'll find a way to synchronize mine up to that. Comparing /proc/config.gz didn't give me a clue.

Thank you for looking into that. Which version of the mainline kernel based Armbian is considered most "stable" for the A20-SOM204 at this time? We're developing a product derived from the A20-SOM204 and want to ensure we are current for security updates, etc at the time of release.

Best Regards,
Jon

[LubOlimex]

Well, the ones we have used in our latest releases seem good enough, we used kernel 5.1.12 next sunxi and Armbian-build 5.89.