Hi Felipe, On Thu, Oct 10, 2013 at 12:44:05PM -0500, Felipe Balbi wrote: > Hi, > > On Fri, Oct 11, 2013 at 01:13:57AM +0800, Huang Rui wrote: > > On Thu, Oct 10, 2013 at 11:26:47AM -0500, Felipe Balbi wrote: > > > HI, > > > > > > On Thu, Oct 10, 2013 at 11:45:47PM +0800, Huang Rui wrote: > > > > On Thu, Oct 10, 2013 at 10:10:52AM -0500, Felipe Balbi wrote: > > > > > On Tue, Oct 08, 2013 at 10:28:29AM -0400, Alan Stern wrote: > > > > > > > > I also have a question for host and device mode switch at DWC3 > > > > controller with on PCI bus. I saw omap glue get extcon cable state to > > > > identify ID pin, am I right? > > > > > > > > if (extcon_get_cable_state(edev, "USB-HOST") == true) > > > > dwc3_omap_set_mailbox(omap, OMAP_DWC3_ID_GROUND); > > > > > > > > But I don't find any similar identification on PCI glue. So how PCI > > > > glue execute this action? > > > > > > OMAP is peculiar. Long story short, IP team always gives us some "nice" > > > easter eggs heh. In this case, ID pin status doesn't go straight from > > > transceiver to dwc3. Transceiver doesn't even know about the ID pin (or > > > vbus) states, those two lines are routed to a discrete comparator and we > > > need to manually write those to that mailbox you see. > > > > > > > So do you mean omap is able to use any other external connector to > > identify ID pin status, not only use transceiver? > > no, I mean that OMAP's internal PHYs don't know anything about the > analog side of USB (VBUS and ID comparators) so you need discretest to > take care of that. That creates the need for some mechanism to pass VBUS > and ID status to the internal PHYs and to DWC3, that mechanism is the > mailbox you see us fiddling with. > I got it. > > > On PCI land I'm assuming this won't be the case and ID/VBUS lines are > > > routed directly to a PHY with internal VBUS and ID comparators. If you > > > want to *force* the IP into host mode, there's a debugfs for that. Just > > > write "host" to /sys/kernel/debug/dwc3*/mode. > > > > > > > So if PCI land, we can't use internal ID pin status to switch the > > roles between host and device. we only should configure the role at > > user space by ourseleves for role switch, am I right? :) > > it depends on how the IP was integrated and which PHY is used. I can't > answer for every possible incarnation of the DWC3 IP using a PCI bridge > around it, sorry. > > In any case, just try it out. 99% of the cases I'd expect the correct > cable to switch correct roles. > > Well, there is the register mirroring problem with DWC3 which I'm tired > of discussing in this list and outside of it, so I'd really suggest > trying things out and seeing how host and device side registers behave. > > Hint: some of those registers will corrupt and break functionality. > There are quite a few folks working on an acceptable workaround until we > have a test setup with dwc3 2.50a. > Thanks a lot for your information! It's very helpful for me. Alan, sorry for my noise. Thanks, Rui -- 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
