[Liverpool] Re: Liverpool Digest, Vol 127, Issue 1

[Andrew Williams]

On 14/04/2008, John Bywater <johnbywr at googlemail.com> wrote:
> Hi Andy
>
> Thanks for that information, but I don't have a problem with using the modem
> now. It is just that the performance is so poor that I am trying to see if
> it is the drivers in the generic usbserial or the ISP who are 'three' at
> fault. I would assume that the ISP is as usual restricting the usage in some
> form or other?
>
> The modem being as you say in two parts. The first storage part loads first,
> if it can, then the second part shows itself which is the modem. As I do a
> fresh boot each time, I have no problem as by the time the modem shows
> itself to the system the boot system has not reach the hardware detection
> stage. So I do a modprobe and then the modified wvdial.
>
> When I download any data the MAX speed that i have had is 61.1 kb/s. On what
> I am told is a 2.8 Mb/s and should do 3.6 mb/s according to the sales
> people. The company seem to think that what speed I am getting is perfectly
> reasonably?
>

It's a buffer limit within the usbserial module, the small buffer is
limiting the max speed that can be sent over usbserial. It would be OK
if your using a proper RS232 connection but for the likes of 3g modems
it needs a bit more legroom to support the full speed.

http://www.junxion.com/opensource/linux_highspeed_usbserial.html

Thats a nasty hack to the usbserial core, best way to go about it
(accordingly) is to use the airprime driver, i think 2.4.24 has it
already in the airprime driver (not too clear from the git commit
logs).


-- 
Andrew Williams
w: http://tensixtyone.com/
e: andy at tensixtyone.com