v3.5 Oops in i2c_algo_bit.c:bit_xfer+0x23/0x870: i915 or i2c?

["George Spelvin" <linux@xxxxxxxxxxx>]

I'm trying to run a v3.5 kernel (plus some -stable patches from Ted Ts'o) on
an Ubuntu system.  Things are generally working except for the following
Oops on each boot, which prevents the graphics system from loading.

[   36.187972] [drm] Initialized drm 1.1.0 20060810
[   36.230306] kvm: VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL does not work properly. Using workaround
[   36.487606] i915 0000:00:02.0: setting latency timer to 64
[   36.555464] [drm] GMBUS [i915 gmbus ssc] timed out, falling back to bit banging on pin 0
[   36.555490] BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
[   36.555626] IP: [<ffffffffa01807b3>] bit_xfer+0x23/0x870 [i2c_algo_bit]
[   36.555701] PGD 212cb0067 PUD 212caf067 PMD 0 
[   36.555803] Oops: 0000 [#1] SMP 
[   36.555885] CPU 3 
[   36.555907] Modules linked in: snd_seq_midi joydev i915(+) snd_rawmidi snd_seq_midi_event snd_seq drm_kms_helper snd_timer snd_seq_device kvm_intel drm kvm snd serio_raw soundcore i2c_algo_bit snd_page_alloc lpc_ich video mei microcode mac_hid eeprom it87 hwmon_vid coretemp lp parport raid10 raid456 async_pq async_xor firewire_ohci firewire_core xor async_memcpy async_raid6_recov hid_microsoft floppy crc_itu_t r8169 pata_jmicron usbhid hid mptsas mptscsih mptbase scsi_transport_sas raid6_pq async_tx raid1 raid0 multipath linear
[   36.557232] 
[   36.557271] Pid: 623, comm: modprobe Not tainted 3.5.0 #3 Gigabyte Technology Co., Ltd. H57M-USB3/H57M-USB3
[   36.557398] RIP: 0010:[<ffffffffa01807b3>]  [<ffffffffa01807b3>] bit_xfer+0x23/0x870 [i2c_algo_bit]
[   36.557493] RSP: 0000:ffff880212c6d648  EFLAGS: 00010296
[   36.557544] RAX: ffff88021222c030 RBX: ffff880212c6d7e8 RCX: 0000000000000000
[   36.557599] RDX: 0000000000000001 RSI: ffff880212c6d7e8 RDI: ffff88021222c030
[   36.557655] RBP: ffff880212c6d6c8 R08: 0000000000000402 R09: 0000000000000000
[   36.557710] R10: 0000000000000000 R11: 0000000000000006 R12: 0000000000000001
[   36.557766] R13: ffff880212c6dfd8 R14: 0000000000000001 R15: ffff88021222c030
[   36.557822] FS:  00007f5a7b85b700(0000) GS:ffff88021fcc0000(0000) knlGS:0000000000000000
[   36.557899] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[   36.557950] CR2: 0000000000000028 CR3: 0000000212cad000 CR4: 00000000000007e0
[   36.558006] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   36.558062] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[   36.558119] Process modprobe (pid: 623, threadinfo ffff880212c6c000, task ffff88020fdf5b80)
[   36.558197] Stack:
[   36.558239]  0000000000000001 ffff880212c6dfd8 0000000000000001 000000011222c000
[   36.558380]  ffff880212c6d6c8 ffffffff8166341e ffff88020ff6ca72 000c510c00000018
[   36.558523]  ffff880212c6d6d8 ffff880212c6d698 0000000000000082 ffff880212c6d7e8
[   36.558671] Call Trace:
[   36.558719]  [<ffffffff8166341e>] ? printk+0x61/0x63
[   36.558790]  [<ffffffffa02e5a0b>] gmbus_xfer+0x56b/0x6f0 [i915]
[   36.558847]  [<ffffffff814ee7dc>] i2c_transfer+0x9c/0xe0
[   36.558899]  [<ffffffff811be91b>] ? ep_poll_callback+0x10b/0x150
[   36.558953]  [<ffffffff814ee976>] i2c_smbus_xfer_emulated+0x156/0x5d0
[   36.559010]  [<ffffffff81321d25>] ? idr_get_empty_slot+0x115/0x320
[   36.559064]  [<ffffffff814eefb3>] i2c_smbus_xfer+0x113/0x130
[   36.559118]  [<ffffffff8166e51e>] ? _raw_spin_lock+0xe/0x20
[   36.559173]  [<ffffffff81642fd9>] ? klist_next+0x89/0x110
[   36.559225]  [<ffffffff814ef61b>] i2c_default_probe+0xeb/0x130
[   36.559279]  [<ffffffff814ee18b>] ? i2c_check_addr_busy+0x3b/0x60
[   36.559332]  [<ffffffff814f077b>] i2c_do_add_adapter+0x1bb/0x290
[   36.559382]  [<ffffffff811ed1cb>] ? sysfs_do_create_link+0xeb/0x200
[   36.559433]  [<ffffffff81411897>] ? put_device+0x17/0x20
[   36.559482]  [<ffffffff814f0880>] ? __process_new_driver+0x30/0x30
[   36.559535]  [<ffffffff814f0892>] __process_new_adapter+0x12/0x20
[   36.559590]  [<ffffffff814140ee>] bus_for_each_drv+0x4e/0xa0
[   36.559642]  [<ffffffff814f029d>] i2c_register_adapter+0x16d/0x270
[   36.559696]  [<ffffffff814f0443>] i2c_add_adapter+0xa3/0xb0
[   36.559759]  [<ffffffffa02e5cfc>] intel_setup_gmbus+0xcc/0x1f0 [i915]
[   36.559821]  [<ffffffffa02a938c>] i915_driver_load+0x2ac/0xb90 [i915]
[   36.559882]  [<ffffffffa03f1b41>] ? drm_get_minor+0x261/0x300 [drm]
[   36.559940]  [<ffffffffa03f4236>] drm_get_pci_dev+0x186/0x2d0 [drm]
[   36.559995]  [<ffffffff8103c3e9>] ? default_spin_lock_flags+0x9/0x10
[   36.560060]  [<ffffffffa02f2142>] i915_pci_probe+0x16/0x20 [i915]
[   36.560115]  [<ffffffff813522ac>] local_pci_probe+0x5c/0xd0
[   36.560168]  [<ffffffff81352431>] pci_device_probe+0x111/0x120
[   36.560221]  [<ffffffff81415ede>] driver_probe_device+0x7e/0x220
[   36.560274]  [<ffffffff8141612b>] __driver_attach+0xab/0xb0
[   36.560327]  [<ffffffff81416080>] ? driver_probe_device+0x220/0x220
[   36.560375]  [<ffffffff81414195>] bus_for_each_dev+0x55/0x90
[   36.560421]  [<ffffffffa0323000>] ? 0xffffffffa0322fff
[   36.560470]  [<ffffffff814158de>] driver_attach+0x1e/0x20
[   36.560522]  [<ffffffff81415598>] bus_add_driver+0x198/0x270
[   36.560573]  [<ffffffffa0323000>] ? 0xffffffffa0322fff
[   36.560625]  [<ffffffff814167f7>] driver_register+0x77/0x150
[   36.560677]  [<ffffffffa0323000>] ? 0xffffffffa0322fff
[   36.560729]  [<ffffffff8135110e>] __pci_register_driver+0x5e/0xe0
[   36.560784]  [<ffffffffa0323000>] ? 0xffffffffa0322fff
[   36.560839]  [<ffffffffa03f449a>] drm_pci_init+0x11a/0x130 [drm]
[   36.560892]  [<ffffffffa0323000>] ? 0xffffffffa0322fff
[   36.560949]  [<ffffffffa032308b>] i915_init+0x8b/0x8d [i915]
[   36.561004]  [<ffffffff8100212a>] do_one_initcall+0x12a/0x180
[   36.561057]  [<ffffffff810af280>] sys_init_module+0x10b0/0x1f40
[   36.561111]  [<ffffffff810ab760>] ? free_notes_attrs+0x60/0x60
[   36.561165]  [<ffffffff81676769>] system_call_fastpath+0x16/0x1b
[   36.561218] Code: 5d c3 45 31 ff eb e9 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 58 66 66 66 66 90 48 8b 4f 18 49 89 ff 48 89 f3 89 55 9c <48> 8b 41 28 48 89 4d 90 48 85 c0 74 0c ff d0 85 c0 89 c1 0f 88 
[   36.562478] RIP  [<ffffffffa01807b3>] bit_xfer+0x23/0x870 [i2c_algo_bit]
[   36.562544]  RSP <ffff880212c6d648>
[   36.562584] CR2: 0000000000000028
[   36.562667] ---[ end trace f73eb7bcfaa57c45 ]---

As far as I can tell, the passed i2c_adap->algo_data is NULL,
so the fetch of adap->pre_xfer is oopsing.

Unfortunately, I'm trying to run ext4 + metadata_csum, which requires
3.5+patches.  I don't see anything relevant on the mailing list.
Do any DRM hackers have any ideas what's up?

System is an i3-530 with 8GiB of RAM.  (Its primary job is
file server, but the display also gets used sometime.)

Thanks!
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