On Sun, May 22, 2011 at 12:51 PM, Robert Jarzmik <robert.jarzmik@xxxxxxx> wrote: > On 05/21/2011 08:35 PM, Dmitry Eremin-Solenikov wrote: >> >> My question is what would be better: to extend gpio-vbus to work w/o >>>> >>>> VBUS pin or to write new transceiver driver only handling gpio-pullup? >>> >>> My personnal feeling is neither, let them be. The generic pullup would >>> have to ask itself : >>> - should the pullup be applied on D+ (on USB 2.0 and 3.0 devices) ? >>> - should the pullup be applied on D- (on USB 1.1 devices) ? >> >> gpio-vbus driver doesn't do this. It simply handles D+ pullup. I think I'd >> start with simple D+ pullup driver and the one may add D- functionality >> if required. > > OK, as long as you don't touch the code in pxa27x_udc.c. Let's do it step by step. My plan would be to drop all non-tranceiver code for handling pullup and VBUS from both pxa25x_udc and pxa27x_udc. >>> >>> The common driver will have to handle the suspend/resume in an >>> homogenous way. >> >> Do pxa25x_udc/pxa27x_udc handle pullup during suspend/resume? > > At least pxa27x_udc does, on suspend to RAM (you should look at > pxa_udc_suspend()). I see... Thanks for pointing to it. >>> >>> If the gadget driver is removed, the pullup should be pulled low. >>> >>> All of this work for only 2 drivers looks overkill to me. >> >> 3 boards only from PXA. I don't know about other platforms/soc-families. > > One other point I've forgotten is that pxa27x_udc in its current state only > supports gpio pullup/pulldown (ie. an external transciever handles D+ > stimulation). But the PXA sillicon has an internal transciever which can be > handled directly by pxa27x_udc (register UP2OCR). > > Now, nobody uses it. If a board manufacturer is crazy enough to use it, the > pullup can only be done from inside the pxa27x_udc driver (IO mappings > driving). Actually I've thought about this. At least several boards use UP2OCR handling (balloon3, collibri, cm-x300, em-x270, spitz, stargate, voipac, zeus). > I still think this driver is a bad idea. But if you wish to do it, go ahead. > The only thing I'll block is removing the existing pullup code from > pxa27x_udc.c. Even if I provide full replacement (from the pulldown-on-suspend POV)? -- With best wishes Dmitry -- 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
