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.)
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)
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.
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)
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....
Looking for comments,
Best regards,
Maxim Levitsky
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