On Wed, 11 Feb 2015, Bin Liu wrote: > Felipe, > > On Wed, Feb 11, 2015 at 2:03 PM, Felipe Balbi <balbi@xxxxxx> wrote: > > On Wed, Feb 11, 2015 at 12:54:52PM -0600, Bin Liu wrote: > >> Peter, > >> > >> On Tue, Feb 10, 2015 at 10:08 PM, Peter Stuge <peter@xxxxxxxx> wrote: > >> > Bin Liu wrote: > >> >> I have a ARM SoC which has a dwc3 drd controller, to validate if there > >> >> is a limit of max device connections, I connected multiple hubs, then > >> >> keyboards and mice. > >> >> > >> >> When plugged in the 32th device, xHCI shows the following message and > >> >> the numeration failed. > >> >> > >> >> Not enough host controller resources for new device state. > >> >> can't set config #1, error -12 Can't set config means the device was enumerated. So there were enough device slots; the problem was some other sort of resource. > >> >> Then plugging in more keyboards or mice, this message always happened. > >> >> But then MSC devices were still enumerated correctly at this point. So > >> >> it seems the issue is only related to interrupt transfers? Probably the resource is connected with scheduling of periodic transfers (interrupt and isochronous). > >> >> I am trying to understand if this is hardware or xHCI driver > >> >> limitation. Anyone has any pointers how to debug this issue? > >> > > >> > I don't know if it is the reason for what you experience above, but > >> > xHCI allows for host controller hardware to limit the number of > >> > devices that can successfully be attached - which IMO permits xHCI > >> > host controllers to be generally incompatible with the USB > >> > specification. > >> > > >> > http://marc.info/?l=linux-usb&m=139654353325844 > >> > >> Thanks for the pointer. I checked HCSPARAMS1 register on my platform, > >> its value is 0x02000440, which means it has 64 device slots. So I > >> think my issue is on elsewhere. > >> > >> Keep looking... > > > > no, you're hitting the limit alright :-) You said it dies after the 32nd > > device right ? I think each device is taking up 2 slots. > > I am still reading, I thought each device takes one slot. Also MSC > device still got enumerated after keyboard failed, that is why I don't > think this is slot limitation problem. > > The failure point varies in my test, sometimes it failed at 32nd, > sometimes at 28th. > > > > > Just a guess, probably worth counting how many slots are used by each > > device. > > Trying to figure out where to patch the driver... > > The error message means ep configuration failed, trying to understand > what ep means in xhci, I don't it is the same as that in musb... The > SoC datasheet says the dwc3 has 15-in + 15-out eps, plus ep0. The problem probably isn't the number of endpoints, but rather the scheduling entries for interrupt and isochronous endpoints. 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
