Back with the 2.4 kernel, using the same config.
one minor change, noticed that stty (a busybox option) is required to change serial port settings of USB serial devices. setserial doesn't cut it.
i can telnet ro 2.4 right away, no problem.
root@OpenWrt:/www/packages# ipkg install kmod-usb-serial_220.127.116.11-brcm-2.4-1_mipsel.ipk
Installing kmod-usb-serial (18.104.22.168-brcm-2.4-1) to root...
root@OpenWrt:/www/packages# ipkg install kmod-usb-serial-pl2303_22.214.171.124-brcm-2.4-1_mipsel.ipk
Installing kmod-usb-serial-pl2303 (126.96.36.199-brcm-2.4-1) to root...
Module Size Used by Tainted: P
pl2303 13896 0 (unused)
usbserial 23884 0 [pl2303]
usb-storage 69632 1
wlcompat 9504 0 (unused)
usb-ohci 19252 0 (unused)
sd_mod 12500 2
ip_conntrack_tftp 1712 0 (unused)
ip_nat_irc 2336 0 (unused)
ip_conntrack_irc 3128 1
ip_nat_ftp 2960 0 (unused)
ip_conntrack_ftp 4272 1
vfat 11340 1
fat 34448 0 [vfat]
ext2 40304 0
wl 665824 0 (unused)
usbcore 71296 1 [pl2303 usbserial usb-storage usb-ohci]
scsi_mod 66048 2 [usb-storage sd_mod]
switch-robo 5052 0 (unused)
switch-core 4928 0 [switch-robo]
diag 28032 0 (unused)
hub.c: new USB device 00:03.0-1, assigned address 5
usbserial.c: PL-2303 converter detected
usbserial.c: PL-2303 converter now attached to ttyUSB0 (or usb/tts/0 for devfs)
# stty -F /dev/usb/tts/0 9600 -ctrscts ( i use the "9600 -ctrscts" settings for my particular application - yours may be different )
stty has a lot of settings, covering several decades of legacy serial devices.
so far the only tests I have done involve a simple loopback, taking a piece of wire and shorting out pins 2-3 on the RS232 part of the serial port adaptor. that part works - but it's not perfect by far.
what i mean by this is that i know the right data is being sent down the cable when i do an internal loopback, but when i try sending my data out to the device i still lose characters and get garbage - due to the limitations of the ancient device i have which requires hardware flow control - a feature lacking here.
my options are to reduce my baud rate and cross my fingers or try the serial port mod again.
maybe just start from the stock configuration again and remember to use stty to actually set the prolific serial port parameters to jive properly with your serial device.
i say this because of my recent adventure and also because others on this forum, albeit a long time ago, have complained that a reboot occured until they used the stty command to set the port parameters correctly.
let me know if you still need help - there are still a large number of reasons why your USB<->Serial reboot could be happening.
it may be easier to just do the serial port mod - after all, you don't have to devote /dev/tts/0 to be a console... just change kernel boot options - edit the .config file manually and remove the 'console= ...' part and also remember to change /etc/inittab too, commenting out the tts/0 line like so:
# tts/0::askfirst:/bin/ash --login
again, the serial mod on the wl-520gu makes more sense in my case, as i'm using a serial port for simple uni-directional communication with an old tll printer that requires DTR/DSR, a feature distinctly lacking on my particular prolific 2303
I'm going to keep working at the USB storage problem now. I do not believe at this time that the USB storage reboots are related to the problem you were having with the prolific serial port.