Re: [9fans] Porting plan9

[Steven Stallion <sstallion@gmail.com>]

On Tue, Dec 2, 2014 at 8:10 AM, erik quanstrom <quanstro@quanstro.net> wrote:
>> One of the functions u-boot performs is configuring the various subsystems
>> in the SoC (individual clocks and power settings for subcomponents, gpio
>> pin functions, ...) -- things a BIOS would do in a more old-timey computer.
>> In my experience these are typically undocumented (or worse, incorrectly
>> documented), so doing this initialisation in Plan 9 would require reverse
>> engineering of u-boot to figure out what to do.  It's easier just to be
>> lazy and let u-boot do it.
>
> that's interesting.  with the marvell chip and board i had, there was almost no
> setup code required.  and what setup code there was, the hardware guy had got
> wrong.

That project was a little different. Off the shelf SoC's (particularly
those targeted for mobile) usually have firmware blobs that have to be
loaded at specific addresses, (undocumented) clock trees, signed stage
1 loaders, and other bits. Many times, using u-boot is your only
choice. You can pick apart the source if you like, but honestly why do
the work? I'm more interested in porting the kernel than writing a
bootloader. Frankly, purity in a software system only exists if you've
also designed the hardware.

Steve