[U-Boot] Debugging, Why USB is not stable

[Detlev Zundel <dzu@denx.de>]

Hi Remy,

>> Only the fact that USB is a nightmare to work with. ?No, honestly, we
>> have a continuous stream of USB related problems with the current USB
>> code.
>
> This is not what I notice on the amount of fixes that are posted on the list...

Most problems go without a fix if there is an easy hardware replacement.
Even diagnosing such a problem is usually too expensive for customers.

> The only fixes I have seen the last year or two were related to newly
> added host-controller support. Apart from that it is quite silent in
> the u-boot-usb tree...
> But, anyway. I know it has some stability issues, although it is now
> much better compared to a year ago...

Yes it is and without a question I greatly appreciate your work for the
USB part.

>>?As I understand it this results from the ever more diverging USB
>> implementation in U-Boot and e.g. in the Linux kernel.
>
> Indeed, It has diverged that much that I did not succeed in finding
> the real origin of the code...
>
>> Sometimes I get the impression that we would save a lot of headache by
>> starting afresh and porting the current Linux code into U-Boot thus
>> leverage all this, but nobody yet dared to start such a feat.
>
> Hey... I have dared to start it!
> (But it is a real pain to do it properly, and I stopped half way due
> to lack of time...)

I can understand that also.  My intention of the mail was to transport
my personal view of the whole area.  USB problems in my experience have
a very high cost even to diagnose, let alone fix.

Cheers
  Detlev

-- 
Test applications  with a variety of tools.  Don't assume everything works if
you've tested  with only  one client.  Also, assume the low end of technology
for clients and don't create applications which can only be used by Graphical
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