[U-Boot] Booting from network

[Simon Goldschmidt]

Am 07.04.2019 um 01:22 schrieb Chris Packham:
> On Sun, 7 Apr 2019, 9:03 AM U.Mutlu, <for-gmane at mutluit.com> wrote:
> 
>> I'm booting over the network (GbE) from a tftp server.
>> It works, but is IMHO very slow.
>> Is there a faster method for booting over the net?
>>
> 
> TFTP is about as good as your going to get in u-boot right now.

There were some patches for wget on the list (implementing TCP, HTTP and 
wget command), but I don't think they were in a state to be accepted, so 
yes, TFTP is pretty much the only option here.

> 
> Because TFTP sends a block at a time waiting for an ack between blocks it's
> not going to be as fast as something that runs over TCP and benefits from
> buffering.

Depending on what stability you need: I saw some TFTP servers (the one 
included in www.dhcpserver.de, for example) in the past that sent out 
some packets in advance (before waiting for the client's ACK). That 
improves speed pretty well, but the downside is that retransmission 
handling is pretty much broken. For my purposes (no transmission 
problems on the local net), this is still a good enough solution to get 
higher transmission speed. I wouldn't want to use this in a production 
setup though...

Regards,
Simon

> 
> One tunable you might get some use out of is $tftpblocksize, this will
> increase the number of bytes per block. Try setting this to around 1400
> keeping the overall Ethernet frame under 1518.
> 
> boot.cmd:
>> dhcp 0x49000000
>> tftpboot 0x46000000 192.168.1.201:uImage
>> tftpboot 0x49000000 192.168.1.201:u-boot.dtb
>> setenv bootargs console=ttyS0,115200 root=/dev/sda1 rootwait panic=10
>> rootfstype=ext4 rw ${extra}
>> bootm 0x46000000 - 0x49000000
>>
>> Btw, in the above script, can I safely replace the addresses
>> with ${kloadaddr} and ${fdtaddr} ?
>> I wonder where these variables get set or obtained from.
>> (I saw these variables somewhere on the net, but there was no
>> initialisation,
>> so I assumed it must be something internal/intrinsic, right?)
>>
> 
> To my knowledge the only intrinsics are $loadaddr, $fileaddr and $filesize.
> The latter two are set after a successful load. However plenty of boards
> have $fdtaddr etc in their default environment so you might have acces to
> those depending on your board.
> 
> And: though my board can output via HDMI, I've no monitor attached,
>> and a serial cable (TTY to USB) I don't have at the moment.
>> Is there another method to get the u-boot output (or log) to be sent to a
>> remote host/log?
>>
> 
> I've never used in personally but CONFIG_NET_CONSOLE exists, I believe its
> only good for output.
> 
> I'd still recommend getting a serial cable if your going to be playing with
> u-boot becasue at some point you'll do something that stops your board from
> booting.
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