On 12/19/2011 05:59 PM, Remy Bohmer wrote: > Hi Wolfgang, > > 2011/12/19 Wolfgang Grandegger <w...@grandegger.com>: >> On 12/19/2011 01:51 PM, Vincent Palatin wrote: >>> On Mon, Dec 19, 2011 at 04:07, Wolfgang Grandegger <w...@grandegger.com> >>> wrote: >>>> I just realized that this patch breaks "usb start" on my mx53loco board: >>>> >>>> The device is not found at the first attempt. Obviously, a value of 10 >>>> for bPwrOn2PwrGood seems too short but 20 works fine. Would that be a >>>> resonable compromise? If yes, I could send a patch. >>> >>> This doesn't match the EHCI standard which explicity states that the >>> power should be good after 20ms (paragraph 2.3.9 in EHCI 1.0), so we >>> should probably find whether we are missing another delay somewhere in >>> the generic EHCI code (which used to be hidden and should be fixed) or >>> if i.MX53 is not compliant with the standard and need a special quirk. >> >> I'm not an USB expert but if I look into the hub_power_on() function of >> the Linux kernel it waits at least 100ms (and only once). See: >> >> http://lxr.linux.no/#linux+v3.1.5/drivers/usb/core/hub.c#L567 > > I would prefer a solution in line with the specification, but what is > the reason why Linux takes 100 msec here? > Is that just chosen randomly , or was there a good reason for it? > If there is a good reason (which I assume) I would prefer to follow > Linux here and go for the 100 msec. > > Can you please provide a patch?
OK, should find time tomorrow. Wolfgang. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
