From mboxrd@z Thu Jan 1 00:00:00 1970 From: alexandre.belloni@free-electrons.com (Alexandre Belloni) Date: Thu, 14 May 2015 23:26:53 +0200 Subject: MUSB dual-role on AM335x behaving weirdly In-Reply-To: References: <20150514170700.GN24269@saruman.tx.rr.com> <20150514174031.GP24269@saruman.tx.rr.com> <20150514174907.GQ24269@saruman.tx.rr.com> <20150514190429.GT24269@saruman.tx.rr.com> <20150514192125.GU24269@saruman.tx.rr.com> <20150514192946.GV24269@saruman.tx.rr.com> Message-ID: <20150514212653.GC3338@piout.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. > I just noticed I have the Jumper 36 on on my EVM, which adds 154.7uF > cap on VBUS causing discharge takes ~20sec. After removed the jumper, > which leaves only 4.7uF cap on VBUS, now it only takes ~0.4sec to > generate Disconnect IRQ. Here is the log. > > root@:~# [ 2504.893123] musb-hdrc musb-hdrc.0.auto: usbintr (1) epintr(0) > [ 2504.899198] musb-hdrc musb-hdrc.0.auto: <== DevCtl=99, int_usb=0x1 > [ 2504.912751] zero gadget: suspend > [ 2504.916145] zero gadget: zero_suspend > [ 2505.303937] musb-hdrc musb-hdrc.0.auto: usbintr (20) epintr(0) > [ 2505.310072] musb-hdrc musb-hdrc.0.auto: <== DevCtl=88, int_usb=0x20 > [ 2505.325355] zero gadget: reset config > [ 2507.303288] musb-hdrc musb-hdrc.0.auto: Poll devctl 80 (b_idle) > -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com