[U-Boot] Booting from network

[Chris Packham <judge.packham@gmail.com>]

On Sun, 7 Apr 2019, 9:03 AM U.Mutlu, <for-gmane@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.

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.

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.