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authorJulius Werner <jwerner@chromium.org>2015-01-27 21:20:12 (GMT)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-02-03 23:28:32 (GMT)
commit7fa40910e0bf5ef32eca49595d950cb24f6402bf (patch)
tree40e95d7bf00bf2ca4ed8f25ae9503f780fb6d25a /Documentation/usb
parent7671bd1e97b9fa09aea69e76375ada9534c735a3 (diff)
downloadlinux-7fa40910e0bf5ef32eca49595d950cb24f6402bf.tar.xz
usb: Retry port status check on resume to work around RH bugs
The EHCI controller on the RK3288 SoC is violating basic parts of the USB spec and thereby unable to properly resume a suspended port. It does not start SOF generation within 3ms of finishing resume signaling, so the attached device will drop of the bus again. This is a particular problem with runtime PM, where accessing the device will trigger a resume that immediately makes it unavailable (and reenumerate with a new handle). Thankfully, the persist feature is generally able to work around stuff like that. Unfortunately, it doesn't quite work in this particular case because the controller will turn off the CurrentConnectStatus bit for an instant while the device is reconnecting, which causes the kernel to conclude that it permanently disappeared. This patch adds a tiny retry mechanism to the core port resume code which will catch this case and shouldn't have any notable impact on other controllers. Signed-off-by: Julius Werner <jwerner@chromium.org> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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