David Brownell wrote, On 01/18/2009 02:45 PM: > On Friday 16 January 2009, Vernon Sauder wrote: >> Since the PXA 27x UDC automatically ACK's some control packets such as >> SET_INTERFACE, the gadgets may not get a chance to process the request >> before another control packet is received. The Linux gadgets do not expect >> to receive setup callbacks out of order. The file storage gadget only >> saves the "highest" priority request. > > Hmm, ISTR from waaay back in pre-history that one of the big > differences between PXA 250 and PXA 255 was that PXA 255 had > a way to work around that misfeature. The UDCCFR register > seems to be where that bugfix resided ... yes, set ACM bit > (ACK Control Mode) to make it wait for the driver to set > the AREN (ACK Response ENable) flag. > > Now, while it's true that the PXA UDC designers seem to be > the best rationale for the war-on-some-drugs, it'd still > surprise me to hear that they reverted that design bugfix. > > ... yep, my ancient copy of the pxa27x developer's manual > says they didn't remove that important mechanism. Best to > just use it. > > - Dave Sure enough. That sounds like *exactly* what I was looking for. Robert, do you want to take a crack at this or should I try something? I think you understand the SW-HW interaction of the driver a bit better. -- Regards, Vernon Sauder :) -- 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
