netboot configuration [was: Re: NFS Root with Raspberry Pi (nfs_diskless: no interface)]

[Daniel Braniss]

> On 29 Sep 2015, at 19:05, Ian Lepore <ian at FreeBSD.org> wrote:
> 
> On Tue, 2015-09-29 at 12:24 +0300, Daniel Braniss wrote:
>>> On 27 Sep 2015, at 19:35, Ian Lepore <ian at FreeBSD.org> wrote:
>>> 
>>> On Sun, 2015-09-27 at 19:25 +0300, Daniel Braniss wrote:
>>>>> On Sep 27, 2015, at 7:14 PM, Ian Lepore <ian at FreeBSD.org> wrote:
>>>>> 
>>>>> On Sun, 2015-09-27 at 14:15 +0300, Daniel Braniss wrote:
>>> [...]
>>>>>> I compiled the u-boot-rpi from ports,
>>>>>> the good news:
>>>>>> 	it understands UserPreboot
>>>>>> the bad news:
>>>>>> 	the nfs boot gets stuck after a while.
>>>>>> 
>>>>>> after much trial and error, this is what I do:
>>>>>> 	hit a key to enter U-Boot
>>>>>> then type:
>>>>>> 	setenv loaderdev net
>>>>>> 	boot
>>>>>> 
>>>>>> attaching the console:
>>>>> 
>>>>> I was also experiencing intermittant lockups while loader loads the
>>>>> kernel.  I just wrote it off to failing hardware (I powered my rpi on
>>>>> for the first time in 6-8 months to work on this), since I've never had
>>>>> a problem with netbooting before (it's the only way I've ever booted the
>>>>> rpi).  If it's not just my board going bad, then that's a bit of a
>>>>> mystery.  The only other difference here from what I've always done is
>>>>> setting rootpath and other net config in u-boot instead of letting ubldr
>>>>> get it from dhcp.
>>>> 
>>>> with the stuff from crochet it works, same setup! I am sniffing the net via
>>>> wireshark, and it stops at different positions in the kernel file,
>>>> so the settings of rootpath and other configs are irrelevant.
>>>> the transfer is being done via udp/nfs/v3 (hence added ric :-) maybe
>>>> he can see something we don´t.
>>> 
>>> Hmmm.  What stuff from crochet?  The two components that are in play
>>> here are u-boot itself (it contains the low-level network drivers that
>>> ubldr uses -- it's effectively acting as a bios for ubldr), and ubldr
>>> which contains the higher-level network code.
>>> 
>>> In theory ubldr should be the same in both cases; nothing much has
>>> changed in the loader code for months.  But there are different paths
>>> through the code depending on how it gets the network parms, and I could
>>> easily have glitched something when I added the feature that lets you
>>> set the config with u-boot env vars.
>>> 
>>> The u-boot might be different between a crochet and ports build.  They
>>> both start with gonzo's u-boot 2013.10 sources, but crochet probably has
>>> a slightly different set of patches it applies.
>>> 
>>> -- Ian
>>> 
>> 
>> with the old uboot it boots ok, with the newer/modified it stops at random
>> places reading via udp/nfs/v3 the kernel. it loads correctly all the *.4th files,
>> then starts reading the kernel, and hangs after a random time.
>> 
> 
> I have found that if I let u-boot get an ip address via dhcp then the
> load of the kernel in ubldr never fails (I've had it reboot-looping for
> 24 hours now without a hang).  But without letting u-boot do the dhcp
> thing it hangs pretty much every time.  Substituting a ping <serverip>
> for the dhcp isn't enough to make it reliable.
> 
> I've stopped debugging that whole mess for now to have a quick check
> whether the very latest mainline u-boot (2015.10-rc4) is able to
> netboot.  It sure would be nice to use something modern that has already
> been debugged by others. :)

there is definitely an issue with the net driver in the newer/ports u-boot.
	- tftpboot sometimes works :-)
	- same with nfs
	
via dhcp:
	it should not try tftp load filename if none is supplied, i.e. defaulting to
	<mac-address>.img is wrong!

	i got ubldr loaded via tftp and then bootelf got it running.
	the loaded kernel complained:
		No valid device tree blob found!
	I guess some of the environmet variables got lost

my network is quiet busy, may be thats a factor?
	
> 
>> on another issue, if I type dhcp instead of boot, it loads via TFTP filename,
>> which I set to ubldr/ubldr.bin, it loads and now prompts again,
>> what should the command be? I tried go 0, go 20000, in which case execs
>> the old ubldr :-(
>> 
> 
> The old ubldr had to be launched using 'bootelf', the new ubldr.bin has
> to be launched using "go ${loadaddr}".  While we transition from old to
> new I've been using "dhcp <dhcp parms> && bootelf || go ${loadaddr}" --
> if it's ubldr the bootelf command works; if bootelf fails it fails back
> to using go.
> 
> -- Ian