[Freedombox-discuss] Power on failure

[Jonas Smedegaard]

Excerpts from Sunil Mohan Adapa's message of april 24, 2018 8:34 am:
> I have had cases where I connect the power to my Lime2 and it does not 
> power on. When I disconnect and reconnect the power, it usually works. 
> I guess this might be due to a poor power supply or too many devices 
> connected via USB. I could be wrong.

I have experienced same as above.


> Also, I debug these cases by connecting a USB-serial connector. If 
> there are no boot messages related to u-boot on the serial console, 
> then it has to do with hardware but if the boot gets hung somewhere, 
> we can identify and fix the issue.
> 
> I believe latest version of the Linux kernel also have HDMI out for 
> A20 SOCs. It is worth connecting Lime2's HDMI port to a monitor and 
> see what is happening.

I believe updating kernel does *not* change what gets output to HDMI: 
Stable Debian linux packages support video putput to HDMI fine¹ and has 
not changed since then, but default software wiring² for LIME boards 
specifically has output to serial by default.

For systems using flash-kernel, I believe the least involving tweak for 
redirecting U-boot output to HDMI is to add the following line close to 
the top of the file /etc/flash-kernel/bootscript/bootscr.sunxi:

  setenv console tty1

e.g. like this:

  sed -i -r -e '2asetenv console tty1\n' /etc/flash-kernel/bootscript/bootscr.sunxi


...and then regenerate boot files, e.g. (indirectly) like this:

  dpkg-reconfigure linux-image-...


To tweak linux cmdline options, edit /etc/default/flash-kernel.

Speaking of cmdline options, you might consider adding these to limit 
video buffers (freeing memory for general use):

  LINUX_KERNEL_CMDLINE_DEFAULTS="sunxi_ve_mem_reserve=0 sunxi_g2d_mem_reserve=0 sunxi_fb_mem_reserve=16"

More info at https://linux-sunxi.org/Kernel_arguments


 - Jonas


¹ Recent kernels improves on other HDMI signalling than video (e.g. 
audio) which is unrelated to the issue of getting console messages.

² setup of Device Tree (dtb) files built from U-boot and Linux.
-- 
 * Jonas Smedegaard - idealist & Internet-arkitekt
 * Tlf.: +45 40843136  Website: http://dr.jones.dk/

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