Hi Felipe, On 18/08/2015 16:13, Felipe Balbi wrote: > Hi, > > On Tue, Aug 18, 2015 at 02:36:13PM +0200, Gregory CLEMENT wrote: >> Hi again Felipe, >> >> I sent this email again without the capture because it prevented to be delivered >> to the mailing lists. >> >> On 04/08/2015 21:32, Felipe Balbi wrote: >>> On Tue, Aug 04, 2015 at 04:23:02PM +0200, Gregory CLEMENT wrote: >>>> Hi again, >>>> On 04/08/2015 15:08, Gregory CLEMENT wrote: >>>>> Hi Bin, >>>>> >>>>> On 02/07/2015 19:05, Bin Liu wrote: >>>>>> Hi, >>>>>> >>>>>> On Thu, Jul 2, 2015 at 2:16 AM, Gregory CLEMENT >>>>>> <gregory.clement@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>> Hi Felipe, >>>>>>> >>>>>>> On 27/05/2015 11:42, Alexandre Belloni wrote: >>>>>>>> Hi, >>>>>>>> >>>>>>>> On 26/05/2015 at 09:51:18 -0500, Felipe Balbi wrote : >>>>>>>>> On Thu, May 14, 2015 at 04:36:33PM -0500, Bin Liu wrote: >>>>>>>>>> Alexandre, >>>>>>>>>> >>>>>>>>>> On Thu, May 14, 2015 at 4:26 PM, Alexandre Belloni >>>>>>>>>> <alexandre.belloni@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>>>>> On 14/05/2015 at 16:16:12 -0500, Bin Liu wrote : >>>>>>>>>>>> I think I found the root cause of the problem: board design issue - I >>>>>>>>>>>> bet the custom board has too much cap on VBUS line. It should be < >>>>>>>>>>>> 10uF. >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> We have a custom board that exhibits the issue but it only has a 100nF >>>>>>>>>>> cap on VBUS. >>>>>>>>>> >>>>>>>>>> Have you measured the VBUS discharging? Is there any way to share your >>>>>>>>>> schematics? >>>>>>>>> >>>>>>>>> Alexandre, any further comments ? >>>>>>>>> >>>>>>>> >>>>>>>> Yeah, I have just got more info. >>>>>>>> >>>>>>>> This is the relevant part of the schematic: >>>>>>>> http://free-electrons.com/~alexandre/usb.png >>>>>>>> >>>>>>>> The total VBUS capacitance is 200nF and the USB0 pins are connected >>>>>>>> directly to the AM3358 pins. U1 is actually not fitted. >>>>>>>> >>>>>>>> We didn't measure VBUS discharging but we observe the OTG pin sensing >>>>>>>> stops when plugging an OTG cable without any device. >>>>>>> >>>>>>> Do you have any news about this topic? >>>>>>> >>>>>>> >>>>>>> Is there something else that we can do to help solving this issue? >>>>>> >>>>>> In the case of CONFIG_USB_MUSB_DUAL_ROLE=y and dr_mode=otg, how is the >>>>>> gadget driver configured? It has to be a module not built-in. >>>>> >>>>> Indeed when I configured CONFIG_USB_MUSB_HDRC=m and CONFIG_USB_MUSB_DSPS=m >>>>> it worked seamless. >>>>> >>>> >>>> Actually it didn't worked. And now sometimes I even received continuously >>>> the following message: >>>> >>>> musb_bus_suspend 2484: trying to suspend as a_wait_vfall while active >>> >>> this is likely because your VBUS hasn't dropped below 0.8V fast enough. >>> >>> I could only trigger this message in that situation. Use a scope to poke >>> at VBUS and see how long is takes to reach 0.8V, this could all be cause >>> by too much capacitance on VBUS line. >> >> We got some news: >> "The capacitance on VBUS due to components is 200nF and the additional parasitic >> capacitance will be much smaller than this" >> >> The rail discharge time is ~36ms when an USB drive is removed from the OTG adapter. >> I attached a capture of this. >> >> What do you think about these values? >> >> >> However, "there appears to be a considerable delay between the removal of a usb >> drive and the initiation of the VBUS discharge (maybe ~1 second, I wasn't able >> to measure this time)." > > yeah, this is really weird. I can't think of anything that would make > VBUS discharge slower from a SW point of view. Once you remove the > cable, VBUS is physically removed and there's nothing else charging it. I have more feedback about it: "When I look at it on the oscilloscope this isn't a 'slow discharge' like a slowly draining capacitor, it is a delay between the removal of a device and the initiation of the discharge. The discharge itself is quite fast once it begins, it just seems as if the SOC/driver is taking a long time to notice the cable is disconnected. At this stage, this isn't actually a problem, just odd." While working on this issue we found that the tg_state_a_wait_vrise_timeout case seemed not managed by musb_dsps driver. I've just submitted a patch for it: https://lkml.org/lkml/2015/8/20/507 I made most of my test on a 3.17 kernel and today by using a 4.1 kernel with the patch I have submitted I didn't manage to reproduce the issue. I saw that since 3.17, there were some patches related to the babble interrupts; so maybe it was enough to fix the issue we saw. It is still weird because one month ago I also tested with a 4.1 kernel and I had issues... It needs more testing to see if it is really fixed because the issue comes only time to time. I will keep you inform about our last tests. Thanks, Gregory -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- 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
