Serial console output before Linux boots is very slow, making things such as GRUB barely usable

[andreabolognani]

Drawing the GRUB menu takes almost 20s, which makes interacting with it a real chore.

Other things are not quite as bad, but the performance is still worse than it is on StarFive VisionFive 2, my point of comparison. For example, running "help" at the u-boot prompt results in a similar number of items (257 vs 237) but the time it takes to print them out is very different (almost 3s vs less than 1s).

Note that this is only really the case until Linux is loaded: when interacting with the Linux serial console performance is comparable between the two boards, and something like vim for example is perfectly usable.

I'm going out on a limb here, but is it possible that the u-boot driver for the serial console has simply not received as much love as the Linux driver? If that's the case, perhaps some effort could be put into making it perform more reasonably.

For reference, this is what my minicom configuration looks like:

pu port             /dev/serial/by-id/usb-FTDI_Quad_RS232-HS-if02-port0
pu baudrate         115200
pu bits             8
pu parity           N
pu stopbits         1
pu rtscts           No

The one I use for VF2 is identical except for the "pu port" part.