On Wed, 25 Jul 2012, Paul Zimmerman wrote: > > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] > > Sent: Wednesday, July 25, 2012 12:48 PM > > To: Paul Zimmerman > > Cc: Rajaram R; Michal Nazarewicz; linux-usb@xxxxxxxxxxxxxxx > > Subject: RE: usb : mass storage : short_not_ok for non usb3 udc > > > > On Wed, 25 Jul 2012, Paul Zimmerman wrote: > > > > > > > > I don't understand this either. What's wrong with setting > > > > > > short_not_ok while at SuperSpeed? It shouldn't force the use of a > > > > bounce buffer. > > > > > > > > > > > > > > > > I have just brought back some code removed by patch "usb: fix mass > > > > > storage gadgets to work with Synopsys UDC". > > > > > > > > Maybe while bringing it back you can remove the checks for SuperSpeed. > > > > Is there any reason to keep them? > > > > > > Hi Alan, > > > > > > The problem only arises because at super-speed the MaxPacket size is > > > 1024, which is greater than the sector size of 512. So the whole point of > > > the patch is to fix the SuperSpeed operation, while allowing high-speed > > > devices to operate as they always did. > > > > Don't the mass-storage drivers already operate correctly at SuperSpeed? > > If not, what goes wrong? > > > > Besides, how could the patch possibly affect SuperSpeed operation? > > Everything it does is protected by > > > > if (!gadget_is_superspeed(gadget)) > > > > So I'm afraid I don't understand your point. > > Sorry for not being clear. The original patch: > > http://www.spinics.net/lists/linux-usb/msg52549.html > > was required to make mass-storage work with DWC3 at SuperSpeed. > However, it apparently broke platforms like musb which depend on > short-not-ok being set. The current patch fixes that, by setting > short-not-ok if not running SuperSpeed. DWC3 will still work fine > with this latest patch, since its problem was only with SuperSpeed. Okay, that's fine. But it doesn't answer my earlier question: Is there really any need for the SuperSpeed checks in this patch? In other words, will DWC3 continue to work correctly if short_not_ok is set? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
