On 28.08.2017 17:40, Mason wrote:
On 28/08/2017 10:39, Mathias Nyman wrote:

Could you take a log with the following added debug, without
your extra delays, It should show a bit more about the state
of the controller when we read 0xffffffff

I applied the following patch on top of v4.12-rc1

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index 5e3e9d4c6956..c7ea7d4c801f 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -23,6 +23,7 @@

  #include <linux/slab.h>
  #include <asm/unaligned.h>
+#include <linux/pci.h>

  #include "xhci.h"
  #include "xhci-trace.h"
@@ -1268,7 +1269,10 @@ int xhci_hub_control(struct usb_hcd *hcd, u16 typeReq, 
u16 wValue,
                wIndex--;
                temp = readl(port_array[wIndex]);
                if (temp == ~(u32)0) {
-                       xhci_hc_died(xhci);
+                       struct pci_dev *pdev = to_pci_dev(hcd->self.controller);
+                       xhci_err(xhci, "ClearPortFeat port%d @%p=%x, hcd->state:0x%x 
hcd->flags:0x%x, pci_state 0x%x\n",
+                                       wIndex, port_array[wIndex], temp, hcd->state, 
hcd->flags, pdev->current_state);
+                       WARN_ON(1);
                        retval = -ENODEV;
                        break;
                }


And here are logs I get when I plug/unplug my USB3 device.

[   14.970148] usb 2-2: new SuperSpeed USB device number 2 using xhci_hcd
[   15.003487] usb 2-2: New USB device found, idVendor=0951, idProduct=1666
[   15.010237] usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[   15.017483] usb 2-2: Product: DataTraveler 3.0
[   15.021990] usb 2-2: Manufacturer: Kingston
[   15.026234] usb 2-2: SerialNumber: 002618887865F0C0F8646BFA
[   15.034830] usb-storage 2-2:1.0: USB Mass Storage device detected
[   15.041269] scsi host0: usb-storage 2-2:1.0
[   16.056140] scsi 0:0:0:0: Direct-Access     Kingston DataTraveler 3.0      
PQ: 0 ANSI: 6
[   16.064979] sd 0:0:0:0: [sda] 15109516 512-byte logical blocks: (7.74 
GB/7.20 GiB)
[   16.072978] sd 0:0:0:0: [sda] Write Protect is off
[   16.078076] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, 
doesn't support DPO or FUA
[   16.089417]  sda: sda1
[   16.093050] sd 0:0:0:0: [sda] Attached SCSI removable disk


[   22.152078] pcieport 0000:00:00.0: AER: Uncorrected (Non-Fatal) error 
received: id=0000
[   22.160157] pcieport 0000:00:00.0: PCIe Bus Error: severity=Uncorrected 
(Non-Fatal), type=Transaction Layer, id=0000(Requester ID)
[   22.172051] pcieport 0000:00:00.0:   device [1105:0024] error 
status/mask=00004000/00000000
[   22.180493] pcieport 0000:00:00.0:    [14] Completion Timeout     (First)
[   22.187368] pcieport 0000:00:00.0: AER: Device recovery failed
[   22.885269] xhci_hcd 0000:01:00.0: ClearPortFeat port1 @e0852430=ffffffff, 
hcd->state:0x1 hcd->flags:0x1a5, pci_state 0x0

State is HC_STATE_RUNNING,

Flags bits 0,2,5,7,8 set:
#define HCD_FLAG_HW_ACCESSIBLE          0       /* at full power */
#define HCD_FLAG_POLL_RH                2       /* poll for rh status? */
#define HCD_FLAG_RH_RUNNING             5       /* root hub is running? */
#define HCD_FLAG_INTF_AUTHORIZED        7       /* authorize interfaces? */
#define HCD_FLAG_DEV_AUTHORIZED         8       /* authorize devices? */

And pci state seems to be D0 (according to driver, pdev->current_state)

I can't see anything wrong from xhci/usb point of view.
I'd focus more on the PCI errors in the logs as the cause for reading 
0xffffffff from xhci mmio.

Then again it might be a bit too drastic to kill xhci just because we read 
0xffffffff once
from a mmio xhci register. Maybe we should return an error a couple times 
before actually
tearing down xhci.

This tight check was originally done to detect pci hotplug removed hosts as 
soon as possible.

-Mathias
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