On Tuesday 27 March 2007 19:15:14 Alan Stern wrote: > On Tue, 27 Mar 2007, Maxim Levitsky wrote: > > > Hi, > > I noticed that after suspend/resume cycle all my usb devices are > > unplugged/replugged by uhci driver. > > While it is not that big problem to me, that can be a real problem if a > > device is a flash card with mounted > > file-system, because disappeared device will cause file-system corruption. > > > > I found why this happens. > > > > drivers/usb/host/pci-quirks.c:uhci_check_and_reset_hc checks that the BIOS > > didn't play with USB controller, and on my system > > with or without a USB Legacy support turned on in the BIOS, the BIOS does > > meddle with USB controller, > > > > But I suggest adding a option that will allow the user to bypass that > > check, because for example on my system USB works perfectly > > if I disable the checks that this function does (but I agree that those > > checks are very valuable, since I almost sure that on many systems USB > > won't work without resetting the USB controller.) > > No. It just isn't safe to do that. If the BIOS has done something to the > controller then it may very well have reset the attached devices too. Or > changed their addresses, or done something else equally drastic.
I agree, I was only saying a option to override this check, for users who know that this is not the case. > > > Secondary, this function checks for UHCI_USBCMD_CONFIGURE, that is not set > > on resume, > > According to both UHCI and ICH8 documentation this is software only bit, > > but I didn't find any place in kernel where it is set, > > (But such place exist, because reading from usb IO ports confirm that it is > > set during normal work, I will try to find it) > > It is set in drivers/usb/host/uhci-hcd.c:start_rh(). Thanks a lot, it would take a lot of time to find that out to me, > > > Disabling both check for UHCI_USBLEGSUP and UHCI_USBCMD_CONFIGURE makes all > > usb devices (I have mouse,keyborad, and joystick) > > work fine on resume from ram without this "virtual" replugging. > > The UHCI specification is rather sparse in many respects, and it doesn't > say what the host firmware should or should not do during a resume. So > the driver has to be very conservative and assume that any indication of a > change means that the entire controller must be reset. > > > Suspend to disk still causes "virtual replugging" and I think that > > controller is reset and will unplug/replug devices anyway > > Resolving this problem is very difficult. Maybe it possible to check on > > unplugging event that this caused by suspend if the same device is > > replugged then don't remove/reinstall driver, but this is very difficult to > > implement properly, > > Maybe just refuse to suspend if some valuable device is connected (sorry if > > it is done this way already) > > Long ago I posted a patch that would take care of all this. Not just for > UHCI, but for any USB controller. Maybe I should dig it out, update it, > and submit it. This sounds great, where is it ? .... :-) This will improve linux suspend to ram/disk a lot. > > > Also I want to note that I didn't yet checked any EHCI devices, because I > > don't have any (I am going to buy a usb stick soon) > > But I feel that the above will be true for ehci too.... > > EHCI controllers tend to be better behaved than UHCI controllers, perhaps > because the specification is much more careful to explain what must be > done. In many cases a computer can resume from suspend-to-RAM with all > the EHCI-connected devices still intact. Big thanks, maybe usb stick I am going to buy will work with suspend to ram.... > > Alan Stern > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > Hi, Thanks a lot for so quick reply, I want to note to myself that making a assumptions generally a bad idea, Until now I thought that linux always unplugs/re plugs usb devices on suspend/resume, that this is normal, but it looks that linux is better... :-) Best regards, Maxim Levitsky - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
