4.10-rc3 rpi issues

[Stefan Wahren]

Hi Michael,

> Michael Zoran <mzoran at crowfest.net> hat am 13. Januar 2017 um 21:59 geschrieben:
> 
> 
> On Fri, 2017-01-13 at 21:44 +0100, Stefan Wahren wrote:
> > Hi Michael,
> > 
> > > Michael Zoran <mzoran at crowfest.net> hat am 12. Januar 2017 um 01:26
> > > geschrieben:
> > > 
> > > 
> > > On Wed, 2017-01-11 at 23:22 +0100, Stefan Wahren wrote:
> > > > Hi Michael,
> > > > 
> > > > > Michael Zoran <mzoran at crowfest.net> hat am 11. Januar 2017 um
> > > > > 22:38
> > > > > geschrieben:
> > > > > 
> > > > > 
> > > > > On Wed, 2017-01-11 at 16:46 +0000, Peter Robinson wrote:
> > > > > > On Wed, Jan 11, 2017 at 2:29 PM, Gerd Hoffmann <kraxel at redhat
> > > > > > .com
> > > > > > > 
> > > > > 
> > > > > I'm actually surprised that somebody hasn't tried to upstream
> > > > > the
> > > > > downstream USB driver which has less limitations.  The DWC USB
> > > > > controller is not Broadcom specific so it would apply to more
> > > > > then
> > > > > the
> > > > > RPI.  I would be interested in helping with such an effort and
> > > > > it
> > > > > may
> > > > > even be possibly to write the driver from "scratch".  The
> > > > > hardest
> > > > > part
> > > > > would be getting something like a PI Zero that doesn't have the
> > > > > USB
> > > > > hub
> > > > > soldered onto the board so that it's easy to attach a USB bus
> > > > > analyzer
> > > > > for better debugging.
> > > > 
> > > > This isn't a surprise. A new driver for a platform which is
> > > > already
> > > > supported by a mainline driver won't be accepted. Maybe the dwc2
> > > > driver would have a better quality for bcm2835 if the Foundation
> > > > would use it instead of the separate downstream driver. Instead
> > > > of
> > > > adding new driver it would be better to fix the existing one.
> > > 
> > > The two drivers have a different architecture.  The upstream driver
> > > submits all the I/O to the hardware at once and relies on the
> > > hardware
> > > sorting it out.  When the fixed number of slots are used, it just
> > > breaks.
> > > 
> > > The downstream driver attempts to schedule the I/O in software and
> > > submit it to the hardware piecemeal.
> > 
> > do you mean the microframe scheduler which is also available in dwc2
> > but disabled for bcm2835?
> 
> Very interesting... I didn't know about that feature. Is it disabled on
> bcm2835 because some hardware functionality was intentionally disabled
> for marketing reasons?

i don't know why. But this feature was buggy. 

But Douglas Anderson rewrote this feature last year [1]. Maybe we should give it try now?