[RFC][USB] powerpc: Workaround for the PPC440EPX USBH_23 errata

[Vitaly Bordug]

В Thu, 4 Sep 2008 17:40:49 -0400 (EDT)
Alan Stern <stern at rowland.harvard.edu> пишет:

> On Fri, 5 Sep 2008, Vitaly Bordug wrote:
> 
> > I've started looking this way. Sorry, but this approach is a little
> > bit fragile, and unreliable.
> > 
> > First, it just did not work out in case of usb2 hub with memory
> > stick and keybord plugged - OHCI did not suspend, ehci is hosed and
> > we're happily using hi-speed device on full-speed:
> 
> > Secondly, we may *not* rely on the fact, that OHCI will always have
> > the same suspend policy. Even kicking the code up to the shape when
> > it will automagically suspend in proper timing to get the HW issue
> > around, we cannot be sure that it will persist along kernel
> > lifecycle, and won't require concerned people to kick suspend
> > timings back to the working state subsequently each rc release.
> > 
> > Thirdly, PM is disabled by Kconfig explicitly in case of 44x.
> > Reasoning is not clear at the moment, but I believe that isn't
> > there just in case.
> 
> I assume that's the reason the suggested approach failed.

Oh geez. I may miss some small point, but dunno what made me appear
*that* dense. The kernel was properly rebuilt with Kconfig fixed and
_PM set.
> 
> > > What to do when CONFIG_PM is off is a separate matter.  Let's not
> > > worry about it for now -- especially since, as Matthias suggested,
> > > you can use a USB 2.0 hub.
> > 
> > Not every hub will work (none of available did so far), and it is
> > often not an option for embedded device without rewiring.
> 
> It's odd that your hubs don't work.  What's wrong with them?
> 

well, they do not have transaction translators then. Nothing really
wrong
> > As this touches powerpc stuff only, are there any objections to let
> > powerpc peolple consider if approach suggested earlier is
> > applicable or not?
> 
> I don't mind doing that, provided the changes are cleaned up so that 
> they don't affect people who aren't building kernels for 44x systems.
OK, thanks for review and comments...

--
Sincerely,

Vitaly