Hi , When we try to modprode Xhci-hcd Driver with "dmesg -n 6" command in background , xhci driver loading failed.But if we give dmesg -n 7/5 or any thing its work. When Extended Capability register is being read its given zero insted of 544 value . Here is the Step to reproduce: #dd if=/dev/mtd4 of=/dev/null bs=1M count=64 & #dmesg -n 6 #modprobe xhci-hcd [ 201.479243] xhci xhci.0: WARN: no supported page size [ 201.501273] xhci xhci.0: No Extended Capability registers, unable to set up roothub. [ 201.510278] xhci xhci.0: Couldn't initialize memory 7+0 records in 7+0 records out 7340032 bytes (7.0MB) copied, 6.254078 seconds, 1.1MB/s [ 207.996342] xhci xhci.0: Host not halted after 16000 microseconds. [ 208.004166] xhci xhci.0: Host controller not halted, aborting reset. [ 208.011761] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 208.019847] pgd = 830ec000 [ 208.022547] [00000000] *pgd=030d2831, *pte=00000000, *ppte=00000000 [ 208.028825] Internal error: Oops: 17 [#1] PREEMPT SMP ARM [ 208.034216] Modules linked in: xhci_hcd(+) [ 208.038317] CPU: 2 Not tainted (3.4.14 #14) [ 208.042868] PC is at xhci_mem_cleanup+0x390/0x530 [xhci_hcd] [ 208.048530] LR is at xhci_mem_cleanup+0x384/0x530 [xhci_hcd] [ 208.054185] pc : [<7f0091dc>] lr : [<7f0091d0>] psr: a0000093 [ 208.054189] sp : 83001d30 ip : 836452b0 fp : 0000002f [ 208.065662] r10: 8a7e102c r9 : 8364bbc8 r8 : 00000000 [ 208.070881] r7 : 8364df60 r6 : 8a7e1084 r5 : 800186b0 r4 : 8a7e1000 [ 208.077403] r3 : 00000000 r2 : 00000000 r1 : 00000000 r0 : 20000013 [ 208.083927] Flags: NzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user [ 208.091144] Control: 18c53c7d Table: 030ec04a DAC: 00000015 [ 208.096885] Process modprobe (pid: 179, stack limit = 0x830002f0) [ 208.102973] Stack: (0x83001d30 to 0x83002000) [ 208.107327] 1d20: 00000000 7f012160 8a7e1000 8364dfc0 [ 208.115502] 1d40: 00000001 00000001 00000000 00000000 8364bbc8 7f00a16c 00000000 8000e418 [ 208.123678] 1d60: 8a7e1000 00000008 00000060 8d89a000 000000d0 00000000 0e405000 0e403000 [ 208.131853] 1d80: 00000000 8a74c200 8a7e1000 90a00000 8364dfc0 00000080 00000001 83665ed0 [ 208.140028] 1da0: 0000002f 7f006308 7f006368 8a74c200 00000000 8a74c2a0 00000038 80348bec [ 208.148203] 1dc0: 00000000 000013e5 8364eb98 8d89a000 8364dfb8 8a74c200 00000038 8364dfc0 [ 208.156378] 1de0: 00000000 000013e5 8364eb98 7f0115dc 00000000 8364dfc0 8364dfc8 8364dfc0 [ 208.164552] 1e00: 836a7f98 836a7fa0 8365f4a8 7f014300 0000001c 802c9bd8 802c9bc0 802c8804 [ 208.172727] 1e20: 83000038 8364dfc0 7f014300 8364dff4 00000000 7f017000 0000001c 802c8a0c [ 208.180901] 1e40: 7f014300 802c8980 00000000 802c6fe4 8d82a360 8d8b9538 7f014300 8365f4a8 [ 208.189076] 1e60: 8a7ea900 802c8028 7f012aa0 7f014300 8d82eb40 7f014300 7f014404 83000000 [ 208.197251] 1e80: 00000000 7f017000 000013e5 0000001c 0000002f 802c8f44 00000000 00000000 [ 208.205425] 1ea0: 7f014404 83000000 00000000 7f017000 0000001c 7f017044 83674c80 80008674 [ 208.213599] 1ec0: 8a7b4f40 00000000 00000001 80065b28 000013e5 00000001 00000001 7f014404 [ 208.221774] 1ee0: 7f01444c 830b1c80 00000001 0000001c 0000002f 800645bc 7f014410 00007fff [ 208.229949] 1f00: 00000000 0010c608 0010c5a8 00000000 7f014540 83000000 0010c5c8 908d612c [ 208.238124] 1f20: 908d71ac 0010c5c8 908c2000 0001c81c 908d6aa4 908d68bb 908d8ecc 00014558 [ 208.246298] 1f40: 00014df8 00000000 00000000 0000002d 0000002e 00000024 00000000 00000019 [ 208.254472] 1f60: 00000000 7f0118ac 00000001 7f0118b4 00000001 00000000 00000000 800c0620 [ 208.262646] 1f80: 00000003 0001c81c 00000000 00000000 00000080 8000ea28 83000000 00000000 [ 208.270822] 1fa0: 0010c5a8 8000e880 0001c81c 00000000 76cf0000 0001c81c 0010c5c8 0010c608 [ 208.278996] 1fc0: 0001c81c 00000000 00000000 00000080 0010c718 0010c608 0010c608 0010c5a8 [ 208.287171] 1fe0: 7ef2aa88 7ef2aa78 00023abc 76de1020 60000010 76cf0000 00000000 00000000 [ 208.295366] [<7f0091dc>] (xhci_mem_cleanup+0x390/0x530 [xhci_hcd]) from [<7f00a16c>] (xhci_mem_init+0xdf0/0x1e20 [xhci_hcd]) [ 208.306597] [<7f00a16c>] (xhci_mem_init+0xdf0/0x1e20 [xhci_hcd]) from [<7f006308>] (xhci_gen_setup+0x1ec/0x24c [xhci_hcd]) [ 208.317654] [<7f006308>] (xhci_gen_setup+0x1ec/0x24c [xhci_hcd]) from [<80348bec>] (usb_add_hcd+0x188/0x664) [ 208.327494] [<80348bec>] (usb_add_hcd+0x188/0x664) from [<7f0115dc>] ( xhci_plat_probe+0x19c/0x264 [xhci_hcd]) [ 208.338027] [<7f0115dc>] ( xhci_plat_probe+0x19c/0x264 [xhci_hcd]) from [<802c9bd8>] (platform_drv_probe+0x18/0x1c) [ 208.348993] [<802c9bd8>] (platform_drv_probe+0x18/0x1c) from [<802c8804>] (driver_probe_device+0x88/0x204) [ 208.358649] [<802c8804>] (driver_probe_device+0x88/0x204) from [<802c8a0c>] (__driver_attach+0x8c/0x90) [ 208.368044] [<802c8a0c>] (__driver_attach+0x8c/0x90) from [<802c6fe4>] (bus_for_each_dev+0x50/0x7c) [ 208.377091] [<802c6fe4>] (bus_for_each_dev+0x50/0x7c) from [<802c8028>] (bus_add_driver+0x1ec/0x2ac) [ 208.386224] [<802c8028>] (bus_add_driver+0x1ec/0x2ac) from [<802c8f44>] (driver_register+0x78/0x178) [ 208.395366] [<802c8f44>] (driver_register+0x78/0x178) from [<7f017044>] (init_module+0x44/0x64 [xhci_hcd]) [ 208.405028] [<7f017044>] (init_module+0x44/0x64 [xhci_hcd]) from [<80008674>] (do_one_initcall+0x34/0x174) [ 208.414688] [<80008674>] (do_one_initcall+0x34/0x174) from [<800645bc>] (sys_init_module+0xe0/0x1ae8) [ 208.423913] [<800645bc>] (sys_init_module+0xe0/0x1ae8) from [<8000e880>] (ret_fast_syscall+0x0/0x30) [ 208.433045] Code: eb53899a e5b61084 e1a03001 e1560001 (e4132004) [ 208.439186] ---[ end trace 1b209721f58098ec ]--- [ 208.443831] note: modprobe[179] exited with preempt_count 1 Segmentation fault [1]+ Done dd if=/dev/mtd6 of=/dev/null bs=1M count=7 Thanks shishir tiwari -- To unsubscribe from this list: send the line 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