[Freedombox-discuss] Power on failure
dr at jones.dk
Tue Apr 24 08:51:07 BST 2018
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:
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
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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