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commit 229bc19fd7aca4f37964af06e3583c1c8f36b5d6 upstream. Don't rely on event interrupt (EINT) bit alone to detect pending port change in resume. If no change event is detected the host may be suspended again, oterwise roothubs are resumed. There is a lag in xHC setting EINT. If we don't notice the pending change in resume, and the controller is runtime suspeded again, it causes the event handler to assume host is dead as it will fail to read xHC registers once PCI puts the controller to D3 state. [ 268.520969] xhci_hcd: xhci_resume: starting port polling. [ 268.520985] xhci_hcd: xhci_hub_status_data: stopping port polling. [ 268.521030] xhci_hcd: xhci_suspend: stopping port polling. [ 268.521040] xhci_hcd: // Setting command ring address to 0x349bd001 [ 268.521139] xhci_hcd: Port Status Change Event for port 3 [ 268.521149] xhci_hcd: resume root hub [ 268.521163] xhci_hcd: port resume event for port 3 [ 268.521168] xhci_hcd: xHC is not running. [ 268.521174] xhci_hcd: handle_port_status: starting port polling. [ 268.596322] xhci_hcd: xhci_hc_died: xHCI host controller not responding, assume dead The EINT lag is described in a additional note in xhci specs 4.19.2: "Due to internal xHC scheduling and system delays, there will be a lag between a change bit being set and the Port Status Change Event that it generated being written to the Event Ring. If SW reads the PORTSC and sees a change bit set, there is no guarantee that the corresponding Port Status Change Event has already been written into the Event Ring." Cc: <stable@vger.kernel.org> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.