[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Mon, Aug 03, 2015 at 12:25:11PM -0400, Theodore Ts'o wrote:
> On Mon, Aug 03, 2015 at 05:27:29PM +0200, Daniel Vetter wrote:
> > 
> > Ok I updated fixes-stuff with just 2 patches which seem to be enough to
> > fix it. Plus a patch to convert Linus' hack into something we can keep
> > plus a drive-by WARNING fix in mst that got in the way for me.
> > 
> > Seems to work here in getting rid of the Oops. If this tests out for you
> > too I'll send a pull to Linus.
> 
> I've just tried pulling in your updated fixes-stuff, and it avoids the
> oops and allows external the monitor to work correctly.  However, I'm
> still seeing a large number of drm/i915 related warning messages and
> other kernel kvetching.

Involved a bit of head-scratching since I'm not too familiar with the
watermark code and it gained a lot of complexity for atomic. But the below
patch should be able to fix this WARNING (and it looks like it was a
genuine one). If it works for you I'll bake it into a proper patch.

Thanks, Daniel

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 30e0f54ba19d..ae07fd0c395c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15121,6 +15121,11 @@ void intel_modeset_setup_hw_state(struct drm_device 
*dev,

intel_modeset_readout_hw_state(dev);

+   if (IS_GEN9(dev))
+   skl_wm_get_hw_state(dev);
+   else if (HAS_PCH_SPLIT(dev))
+   ilk_wm_get_hw_state(dev);
+
/*
 * Now that we have the config, copy it to each CRTC struct
 * Note that this could go away if we move to using crtc_config
@@ -15162,11 +15167,6 @@ void intel_modeset_setup_hw_state(struct drm_device 
*dev,
pll->on = false;
}

-   if (IS_GEN9(dev))
-   skl_wm_get_hw_state(dev);
-   else if (HAS_PCH_SPLIT(dev))
-   ilk_wm_get_hw_state(dev);
-
if (force_restore) {
i915_redisable_vga(dev);

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Rafael J. Wysocki]

On Tuesday, August 04, 2015 12:05:14 AM Daniel Vetter wrote:
> On Mon, Aug 3, 2015 at 7:24 PM, Linus Torvalds
>  wrote:
> >>  However, I'm
> >> still seeing a large number of drm/i915 related warning messages and
> >> other kernel kvetching.
> >
> > I suspect I can live with that for now. The lockdep one looks like
> > it's mainly an initialization issue, so you'd never get the actual
> > deadlock in practice, but it's obviously annoying.  The intel_pm.c one
> > I'll have to defer to the i915 people for..
> 
> The lockdep splat is just acpi being inconsistent with init_mutex vs.
> backlight notifier_chain (which has it's own lock) calls. init_mutex
> is new in 4.2 and has been added in
> 
> commit 87521e16a7abbf3fa337f56cb4d1e18247f15e8a
> Author: Hans de Goede 
> Date:   Tue Jun 16 16:27:48 2015 +0200
> 
> acpi-video-detect: Rewrite backlight interface selection logic
> 
> 
> Not mine ;-) But adding relevant people.

Hans, can you have a look at this, please?

Rafael

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Mon, Aug 3, 2015 at 7:24 PM, Linus Torvalds
 wrote:
>>  However, I'm
>> still seeing a large number of drm/i915 related warning messages and
>> other kernel kvetching.
>
> I suspect I can live with that for now. The lockdep one looks like
> it's mainly an initialization issue, so you'd never get the actual
> deadlock in practice, but it's obviously annoying.  The intel_pm.c one
> I'll have to defer to the i915 people for..

The lockdep splat is just acpi being inconsistent with init_mutex vs.
backlight notifier_chain (which has it's own lock) calls. init_mutex
is new in 4.2 and has been added in

commit 87521e16a7abbf3fa337f56cb4d1e18247f15e8a
Author: Hans de Goede 
Date:   Tue Jun 16 16:27:48 2015 +0200

acpi-video-detect: Rewrite backlight interface selection logic


Not mine ;-) But adding relevant people.

I'll send you a pull for the mst one tomorrow and look into the
watermark fail in intel_pm.c too.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Thu, Jul 30, 2015 at 11:50:29AM -0400, Theodore Ts'o wrote:
> On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
> > I have 4 patches in git://people.freedesktop.org/~danvet/drm fixes-stuff
> > but I couldn't test them yet since no dp mst here and I didn't find
> > anything that would ship faster than 1-2 weeks yet. I'll try to get some
> > other people here to test it meanwhile too.
> 
> I've tried pulling in your patches from fixes-stuff, onto Linus's tree
> (without Linus's fix), and the good news is that I'm no longer
> crashing on boot.
> 
> The *bad* news is that (a) it breaks the external monitor attached to
> the docking station completely (this was working with Linus's patch),
> and (b) it's triggering a LOCKDEP failure.
> 
> So even though Linus's patch wasn't supposed to work, I think I'm
> going to back to it

Ok I updated fixes-stuff with just 2 patches which seem to be enough to
fix it. Plus a patch to convert Linus' hack into something we can keep
plus a drive-by WARNING fix in mst that got in the way for me.

Seems to work here in getting rid of the Oops. If this tests out for you
too I'll send a pull to Linus.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Mon, Aug 03, 2015 at 10:24:53AM -0700, Linus Torvalds wrote:
> On Mon, Aug 3, 2015 at 9:25 AM, Theodore Ts'o  wrote:
> >
> > I've just tried pulling in your updated fixes-stuff, and it avoids the
> > oops and allows external the monitor to work correctly.
> 
> Good. Have either of you tested the suspend/resume behavior? Is that fixed 
> too?

No, I haven't had a chance to test the suspend/resume behavior,
because that requires suspending at work, going home, and connecting
to a dock which has a different monitor attached to it, and resuming
(or vice versa of suspending at home and then resuming at work).

So it's a bit trickier for me to test.  It's also not a regression,
and the workaround of rebooting is annoying, but I've lived with it
for several releases now, but I'll try the two patches/changes that
folks had suggested hopefully later this week.

- Ted

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Mon, Aug 03, 2015 at 05:27:29PM +0200, Daniel Vetter wrote:
> 
> Ok I updated fixes-stuff with just 2 patches which seem to be enough to
> fix it. Plus a patch to convert Linus' hack into something we can keep
> plus a drive-by WARNING fix in mst that got in the way for me.
> 
> Seems to work here in getting rid of the Oops. If this tests out for you
> too I'll send a pull to Linus.

I've just tried pulling in your updated fixes-stuff, and it avoids the
oops and allows external the monitor to work correctly.  However, I'm
still seeing a large number of drm/i915 related warning messages and
other kernel kvetching.

Thanks!!

- Ted

[4.084198] [drm] Initialized drm 1.1.0 20060810
[4.129576] [drm] Memory usable by graphics device = 2048M
[4.129616] [drm] Replacing VGA console driver
[4.130315] Console: switching to colour dummy device 80x25
[4.145332] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[4.145334] [drm] Driver supports precise vblank timestamp query.
[4.146184] vgaarb: device changed decodes: 
PCI::00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
[4.163778] usbcore: registered new interface driver btusb
[4.170719] [ cut here ]
[4.170749] WARNING: CPU: 0 PID: 463 at 
/usr/projects/linux/linux/drivers/gpu/drm/i915/intel_pm.c:2339 
ilk_update_wm+0x71a/0xb27 [i915]()
[4.170751] WARN_ON(!r->enable)
[4.170752] Modules linked in:
[4.170754]  btusb btrtl btbcm btintel iwlmvm(+) bluetooth mac80211 iwlwifi 
snd_hda_intel i915(+) drm_kms_helper snd_hda_codec cfg80211 drm snd_hwdep 
lpc_ich snd_hda_core intel_gtt thinkpad_acpi tpm_tis nvram tpm 
intel_smartconnect uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core 
sch_fq_codel kvm_intel kvm ecryptfs parport_pc ppdev lp parport autofs4 btrfs 
xor hid_generic usbhid hid raid6_pq microcode rtsx_pci_sdmmc ehci_pci e1000e 
rtsx_pci ehci_hcd xhci_pci ptp mfd_core pps_core xhci_hcd
[4.170805] CPU: 0 PID: 463 Comm: systemd-udevd Not tainted 
4.2.0-rc5-14194-g130583b #18
[4.170807] Hardware name: LENOVO 20BECTO1WW/20BECTO1WW, BIOS GMET59WW (2.07 
) 02/12/2014
[4.170809]  0009 880403f0f4c8 8161aaee 
0006
[4.170814]  880403f0f518 880403f0f508 8107e5f0 
0006
[4.170818]  c05ade43 8800c8b7 8800c7f16000 
880405fb48b8
[4.170823] Call Trace:
[4.170829]  [] dump_stack+0x4c/0x65
[4.170833]  [] warn_slowpath_common+0xa1/0xbb
[4.170856]  [] ? ilk_update_wm+0x71a/0xb27 [i915]
[4.170859]  [] warn_slowpath_fmt+0x46/0x48
[4.170879]  [] ? ilk_compute_wm_maximums+0x43/0xa2 [i915]
[4.170899]  [] ilk_update_wm+0x71a/0xb27 [i915]
[4.170921]  [] intel_update_watermarks+0x1e/0x20 [i915]
[4.170957]  [] haswell_crtc_disable+0x270/0x2ae [i915]
[4.170989]  [] intel_crtc_control+0xa0/0xe1 [i915]
[4.171020]  [] intel_crtc_update_dpms+0x4d/0x5d [i915]
[4.171052]  [] intel_modeset_setup_hw_state+0x7b0/0xa90 
[i915]
[4.171081]  [] ? hsw_write64+0xcd/0xcd [i915]
[4.171113]  [] ? ilk_fbc_disable+0x29/0x69 [i915]
[4.171142]  [] intel_modeset_init+0x130d/0x14e3 [i915]
[4.171179]  [] i915_driver_load+0xf05/0x1139 [i915]
[4.171183]  [] ? mark_held_locks+0x56/0x6c
[4.171186]  [] ? _raw_spin_unlock_irqrestore+0x3f/0x4d
[4.171189]  [] ? trace_hardirqs_on_caller+0x171/0x18d
[4.171204]  [] drm_dev_register+0x84/0xfd [drm]
[4.171215]  [] drm_get_pci_dev+0x102/0x1bc [drm]
[4.171237]  [] i915_pci_probe+0x4f/0x51 [i915]
[4.171240]  [] pci_device_probe+0x74/0xd6
[4.171245]  [] ? driver_probe_device+0x387/0x387
[4.171248]  [] driver_probe_device+0x15f/0x387
[4.171250]  [] ? driver_probe_device+0x387/0x387
[4.171252]  [] __driver_attach+0x53/0x74
[4.171255]  [] bus_for_each_dev+0x6f/0x89
[4.171257]  [] driver_attach+0x1e/0x20
[4.171260]  [] bus_add_driver+0x140/0x238
[4.171263]  [] driver_register+0x8f/0xcc
[4.171266]  [] __pci_register_driver+0x5e/0x62
[4.171268]  [] ? 0xc069c000
[4.171278]  [] drm_pci_init+0x58/0xda [drm]
[4.171281]  [] ? 0xc069c000
[4.171301]  [] i915_init+0xa0/0xa8 [i915]
[4.171303]  [] ? 0xc069c000
[4.171307]  [] do_one_initcall+0x19a/0x1af
[4.171310]  [] ? do_init_module+0x28/0x1e3
[4.171313]  [] ? kmem_cache_alloc_trace+0xba/0xcc
[4.171315]  [] do_init_module+0x60/0x1e3
[4.171319]  [] load_module+0x1c42/0x2059
[4.171324]  [] SyS_finit_module+0x85/0x92
[4.171327]  [] entry_SYSCALL_64_fastpath+0x16/0x73
[4.171329] ---[ end trace 7eb514b89de5fc4a ]---
[4.171331] [ cut here ]
[4.171354] WARNING: CPU: 0 PID: 463 at 
/usr/projects/linux/linux/drivers/gpu/drm/i915/intel_pm.c:2339 
ilk_update_wm+0x71a/0xb27 [i915]()
[4.171355] WARN_ON(!r->enable)
[4.171357] Modules linked in:
[4.171358]  btusb btrtl

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Linus Torvalds]

On Mon, Aug 3, 2015 at 9:25 AM, Theodore Ts'o  wrote:
>
> I've just tried pulling in your updated fixes-stuff, and it avoids the
> oops and allows external the monitor to work correctly.

Good. Have either of you tested the suspend/resume behavior? Is that fixed too?

>  However, I'm
> still seeing a large number of drm/i915 related warning messages and
> other kernel kvetching.

I suspect I can live with that for now. The lockdep one looks like
it's mainly an initialization issue, so you'd never get the actual
deadlock in practice, but it's obviously annoying.  The intel_pm.c one
I'll have to defer to the i915 people for..

I'll be travelling much of this week (flying to Finland tomorrow, back
on Sunday - yay, 30h in airplanes for three days on the ground, but
it's my dad's bday), and my internet will be sporadic. But I'll have a
laptop and be able to pull stuff every once in a while.

It would be good to have this one resolved, and I just need to worry
about the remaining VM problem..

   Linus

> [4.170749] WARNING: CPU: 0 PID: 463 at 
> drivers/gpu/drm/i915/intel_pm.c:2339 ilk_update_wm+0x71a/0xb27 [i915]()
> [4.170751] WARN_ON(!r->enable)

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Dave Airlie]

On 30 July 2015 at 15:18, Linus Torvalds  
wrote:
> On Wed, Jul 29, 2015 at 6:39 PM, Theodore Ts'o  wrote:
>>
>> It's here:  https://goo.gl/photos/xHjn2Z97JQEw6k2C9
>
> You didn't catch enough of the code line to decode the code, but it's
> early enough in drm_crtc_index() (just five bytes in) that it's almost
> certainly the very first dereference, so it's almost guaranteed to be
> that
>
>crtc->dev
>
> access as part of list_for_each_entry(), with crtc being NULL. And
> yes, "->dev" is the very first field, so the offset is zero too (while
> the "->mode_config" list access would not be at offset zero).
>
> And it looks like it is called from drm_atomic_helper_check_modeset():
> the reason it has a question mark in the backtrace is because the
> fault happens before the stack frame has even been set up.
>
> There are multiple calls to "drm_crtc_index()" from that function, I
> can't tell which one it is. Looking at the code generation I get, I
> think it's because update_connector_routing() gets inlined, and that
> one does several calls. Most of them look like this:
>
> if (connector->state->crtc) {
> idx = drm_crtc_index(connector->state->crtc);
>
> ie they check that the crtc is non-NULL, but that last one does not:
>
> connector_state->best_encoder = new_encoder;
> idx = drm_crtc_index(connector_state->crtc);
>
> crtc_state = state->crtc_states[idx];
> crtc_state->mode_changed = true;
>
> and I suspect the fix might be something like the attached. Totally
> untested. Ted?
>
> This whole "atomic modeset" series has been one royal fuck-up, guys.
> We've had too many of these kinds of crap issues.

It hasn't been that bad, on a scale of 1 to MD eats my raid array, I'd
say we are barely at a 5.

There have been a lot of small and seemingly easily fixed teething
problems, essentially rewriting the DRM API to provide a new userspace
API and internal interface, porting some drivers partly to the new
interface, while trying to maintain the old ABI/API on top seamlessly
was always going to be an impossible task. It was never going to
magically all just work in -next and land in your tree fully formed
smelling of lavender and elderberries. This is a massive undertaking,
and doing it over a few kernels was the only possible way it could
ever land.

I think the biggest problem we've had is the QA team at Intel got
reorganised or something right when they really needed to be doing
testing on this stuff, so what was sitting in -next never got as much
testing as it had previously, and you can see that in the types of
cases that are getting through. I think the other thing we can learn
is that when Android forks the kernel we should just say this shit is
too hard, let Google go and create a new API and a complete set of
graphics drivers and deal with it in 10 years, because that was
seriously the only other option.

So yes it's a pity other kernel developers are seeing our fallout, but
I've experienced lots of other kernel developers fall out over the
years, and generally the idea is to get this stuff fixed to a
reasonable state before you release a final kernel.

Note I'm not personally involved in the development for atomic
modesetting at all, I'm running the kernels with it where and when I
can, and I trust the developers who work on it are doing as much as
they can to make it work.

That said hopefully Daniel can find a bag of fucks to debug and write
a proper patch, instead of rage quitting the universe, and just git
reset --hard v4.0 drivers/gpu/drm/i915..

Dave.

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Thu, Jul 30, 2015 at 11:50:29AM -0400, Theodore Ts'o wrote:
> On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
> > I have 4 patches in git://people.freedesktop.org/~danvet/drm fixes-stuff
> > but I couldn't test them yet since no dp mst here and I didn't find
> > anything that would ship faster than 1-2 weeks yet. I'll try to get some
> > other people here to test it meanwhile too.
> 
> I've tried pulling in your patches from fixes-stuff, onto Linus's tree
> (without Linus's fix), and the good news is that I'm no longer
> crashing on boot.

Ok so I'm not completely clueless yet, the encoder confusion indeed
resulted in the follow-up crash. But obviously I don't understand yet
exactly what's going on if this breaks the display.

> The *bad* news is that (a) it breaks the external monitor attached to
> the docking station completely (this was working with Linus's patch),
> and (b) it's triggering a LOCKDEP failure.

The lockdep splat is all in the driver load before we do any modeset at
all, so shouldn't have changed between these patches. Are you sure it's a
regression due to mine and wasn't there before?

> So even though Linus's patch wasn't supposed to work, I think I'm
> going to back to it

Well I found some dp mst hubs meanwhile so hopefully tomorrow I can test
myself what's going wrong here.
-Daniel

> 
>   - Ted
> 
> 
> Jul 30 11:46:49 closure kernel: [4.221951] 
> Jul 30 11:46:49 closure kernel: [4.221954] 
> ==
> Jul 30 11:46:49 closure kernel: [4.221957] [ INFO: possible circular 
> locking dependency detected ]
> Jul 30 11:46:49 closure kernel: [4.221960] 4.2.0-rc4-13906-g5f1b75cd #16 
> Not tainted
> Jul 30 11:46:49 closure kernel: [4.221963] 
> ---
> Jul 30 11:46:49 closure kernel: [4.221966] modprobe/503 is trying to 
> acquire lock:
> Jul 30 11:46:49 closure kernel: [4.221968]  (init_mutex){+.+.+.}, at: 
> [] acpi_video_get_backlight_type+0x17/0x164
> Jul 30 11:46:49 closure kernel: [4.221977] 
> Jul 30 11:46:49 closure kernel: [4.221977] but task is already holding 
> lock:
> Jul 30 11:46:49 closure kernel: [4.221979]  
> (&(&backlight_notifier)->rwsem){..}, at: [] 
> __blocking_notifier_call_chain+0x37/0x69
> Jul 30 11:46:49 closure kernel: [4.221987] 
> Jul 30 11:46:49 closure kernel: [4.221987] which lock already depends on 
> the new lock.
> Jul 30 11:46:49 closure kernel: [4.221987] 
> Jul 30 11:46:49 closure kernel: [4.221990] 
> Jul 30 11:46:49 closure kernel: [4.221990] the existing dependency chain 
> (in reverse order) is:
> Jul 30 11:46:49 closure kernel: [4.221995] 
> Jul 30 11:46:49 closure kernel: [4.221995] -> #1 
> (&(&backlight_notifier)->rwsem){..}:
> Jul 30 11:46:49 closure kernel: [4.222001][] 
> lock_acquire+0x104/0x18b
> Jul 30 11:46:49 closure kernel: [4.222007][] 
> down_write+0x46/0x8a
> Jul 30 11:46:49 closure kernel: [4.222012][] 
> blocking_notifier_chain_register+0x36/0x57
> Jul 30 11:46:49 closure kernel: [4.222017][] 
> backlight_register_notifier+0x18/0x1a
> Jul 30 11:46:49 closure kernel: [4.222022][] 
> acpi_video_get_backlight_type+0xfa/0x164
> Jul 30 11:46:49 closure kernel: [4.222028][] 
> 0xc03a1e45
> Jul 30 11:46:49 closure audispd: No plugins found, exiting
> Jul 30 11:46:49 closure kernel: [4.222032][] 
> 0xc03a28a8
> Jul 30 11:46:49 closure kernel: [4.222036][] 
> do_one_initcall+0x19a/0x1af
> Jul 30 11:46:49 closure kernel: [4.222042][] 
> do_init_module+0x60/0x1e3
> Jul 30 11:46:49 closure kernel: [4.222047][] 
> load_module+0x1c42/0x2059
> Jul 30 11:46:49 closure kernel: [4.222052][] 
> SyS_finit_module+0x85/0x92
> Jul 30 11:46:49 closure kernel: [4.222056][] 
> entry_SYSCALL_64_fastpath+0x16/0x73
> Jul 30 11:46:49 closure kernel: [4.222060] 
> Jul 30 11:46:49 closure kernel: [4.222060] -> #0 (init_mutex){+.+.+.}:
> Jul 30 11:46:49 closure kernel: [4.222065][] 
> __lock_acquire+0xc55/0xf54
> Jul 30 11:46:49 closure kernel: [4.222070][] 
> lock_acquire+0x104/0x18b
> Jul 30 11:46:49 closure kernel: [4.222074][] 
> mutex_lock_nested+0x70/0x391
> Jul 30 11:46:49 closure kernel: [4.222078][] 
> acpi_video_get_backlight_type+0x17/0x164
> Jul 30 11:46:49 closure kernel: [4.222083][] 
> acpi_video_backlight_notify+0x19/0x2f
> Jul 30 11:46:49 closure kernel: [4.222088][] 
> notifier_call_chain+0x4c/0x71
> Jul 30 11:46:49 closure kernel: [4.222092][] 
> __blocking_notifier_call_chain+0x50/0x69
> Jul 30 11:46:49 closure kernel: [4.222098][] 
> blocking_notifier_call_chain+0x14/0x16
> Jul 30 11:46:49 closure kernel: [4.222103][] 
> backlight_device_regist

[Intel-gfx] [REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Takashi Iwai]

On Thu, 30 Jul 2015 17:32:28 +0200,
Theodore Ts'o wrote:
> 
> On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
> > On Wed, Jul 29, 2015 at 10:18:16PM -0700, Linus Torvalds wrote:
> > >  drivers/gpu/drm/drm_atomic_helper.c | 8 +---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
> > > b/drivers/gpu/drm/drm_atomic_helper.c
> > > index 5b59d5ad7d1c..aac212297b49 100644
> > > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > > @@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state 
> > > *state, int conn_idx)
> > >   }
> > >  
> > >   connector_state->best_encoder = new_encoder;
> > > - idx = drm_crtc_index(connector_state->crtc);
> > > + if (connector_state->crtc) {
> > > + idx = drm_crtc_index(connector_state->crtc);
> > >  
> > > - crtc_state = state->crtc_states[idx];
> > > - crtc_state->mode_changed = true;
> > > + crtc_state = state->crtc_states[idx];
> > > + crtc_state->mode_changed = true;
> > > + }
> > 
> > This shouldn't happen since if it does we ended up stealing the encoder
> > from the connector itself (we do check for connector_state->crtc earlier)
> > and that would be a bug. I haven't figured out a precise theory but my
> > guess is on the best_encoder selection, and indeed dp mst encoder
> > selection seems to have gone belly up in 4.2 with the bisected commit.
> 
> Well, I just tested Linus's patch and it works.
> 
> BTW, is there any chance that I can suspend my laptop, and then move
> it from my docking station at home (where I have a Dell 30" display)
> to my docking station at work (where I have a Dell 24" display), and
> actually have the new monitor be detected?  For at least the past
> year, I have to reboot in order to be able to use the external
> monitor?  This used to work, but it's been a very long-standing
> regression.  I undrstand that Multi-stream DP is a evil horrible hack,
> and supporting it is painful, but this used to work, and it hasn't in
> a long time.  :-(

Relevant with this?
   https://bugs.freedesktop.org/show_bug.cgi?id=89589

I wanted to check this by myself, too, as the same bug was reported to
openSUSE bugzilla, but I had no hardware showing it.


Takashi

[Intel-gfx] [REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Thu, Jul 30, 2015 at 5:32 PM, Theodore Ts'o  wrote:
> On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
>> On Wed, Jul 29, 2015 at 10:18:16PM -0700, Linus Torvalds wrote:
>> >  drivers/gpu/drm/drm_atomic_helper.c | 8 +---
>> >  1 file changed, 5 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
>> > b/drivers/gpu/drm/drm_atomic_helper.c
>> > index 5b59d5ad7d1c..aac212297b49 100644
>> > --- a/drivers/gpu/drm/drm_atomic_helper.c
>> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> > @@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state 
>> > *state, int conn_idx)
>> > }
>> >
>> > connector_state->best_encoder = new_encoder;
>> > -   idx = drm_crtc_index(connector_state->crtc);
>> > +   if (connector_state->crtc) {
>> > +   idx = drm_crtc_index(connector_state->crtc);
>> >
>> > -   crtc_state = state->crtc_states[idx];
>> > -   crtc_state->mode_changed = true;
>> > +   crtc_state = state->crtc_states[idx];
>> > +   crtc_state->mode_changed = true;
>> > +   }
>>
>> This shouldn't happen since if it does we ended up stealing the encoder
>> from the connector itself (we do check for connector_state->crtc earlier)
>> and that would be a bug. I haven't figured out a precise theory but my
>> guess is on the best_encoder selection, and indeed dp mst encoder
>> selection seems to have gone belly up in 4.2 with the bisected commit.
>
> Well, I just tested Linus's patch and it works.

That's sersiously surprising if you mean display and everything actually
works. Is dpms on/off and suspend and all that also still working? Can you
please changed the check into a

if (!connector_state->crtc)
return 0;

so that we don't blow up on the debug line below and then grab dmesg with
drm.debug=0x1e when this happens? Note there will be lots of noise you
might need to dig out full dmesg from logs.

> BTW, is there any chance that I can suspend my laptop, and then move
> it from my docking station at home (where I have a Dell 30" display)
> to my docking station at work (where I have a Dell 24" display), and
> actually have the new monitor be detected?  For at least the past
> year, I have to reboot in order to be able to use the external
> monitor?  This used to work, but it's been a very long-standing
> regression.  I undrstand that Multi-stream DP is a evil horrible hack,
> and supporting it is painful, but this used to work, and it hasn't in
> a long time.  :-(

Hm we seem to not reprobe mst state on resume. The quick hack below should
help (but totally untested since still no dp mst hub here).
-Daniel

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 884b4f9b81c4..c0677c83a0e9 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -775,6 +775,9 @@ static int i915_drm_resume(struct drm_device *dev)
/* Config may have changed between suspend and resume */
drm_helper_hpd_irq_event(dev);

+   dev_priv->short_hpd_port_mask = ~0;
+   queue_work(dev_priv->dp_wq, &dev_priv->dig_port_work);
+
intel_opregion_init(dev);

intel_fbdev_set_suspend(dev, FBINFO_STATE_RUNNING, false);
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Daniel Vetter]

On Wed, Jul 29, 2015 at 10:18:16PM -0700, Linus Torvalds wrote:
>  drivers/gpu/drm/drm_atomic_helper.c | 8 +---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
> b/drivers/gpu/drm/drm_atomic_helper.c
> index 5b59d5ad7d1c..aac212297b49 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state 
> *state, int conn_idx)
>   }
>  
>   connector_state->best_encoder = new_encoder;
> - idx = drm_crtc_index(connector_state->crtc);
> + if (connector_state->crtc) {
> + idx = drm_crtc_index(connector_state->crtc);
>  
> - crtc_state = state->crtc_states[idx];
> - crtc_state->mode_changed = true;
> + crtc_state = state->crtc_states[idx];
> + crtc_state->mode_changed = true;
> + }

This shouldn't happen since if it does we ended up stealing the encoder
from the connector itself (we do check for connector_state->crtc earlier)
and that would be a bug. I haven't figured out a precise theory but my
guess is on the best_encoder selection, and indeed dp mst encoder
selection seems to have gone belly up in 4.2 with the bisected commit.

I have 4 patches in git://people.freedesktop.org/~danvet/drm fixes-stuff
but I couldn't test them yet since no dp mst here and I didn't find
anything that would ship faster than 1-2 weeks yet. I'll try to get some
other people here to test it meanwhile too.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Thu, Jul 30, 2015 at 11:50:29AM -0400, Theodore Ts'o wrote:
> I've tried pulling in your patches from fixes-stuff, onto Linus's tree
> (without Linus's fix), and the good news is that I'm no longer
> crashing on boot.
> 
> The *bad* news is that (a) it breaks the external monitor attached to
> the docking station completely (this was working with Linus's patch),
> and (b) it's triggering a LOCKDEP failure.

Well, that's not fair.  Even with Linus's fix, there is still a
LOCKDEP failure.  And a few more i915 WARNINGS.  But at least the
external monitor works, so this is what I'm using.  Enclosed please
find a dmesg with the lockdep and i915 warnings and my .config.  The
kernel that I used can be found at:

https://git.kernel.org/cgit/linux/kernel/git/tytso/ext4.git/log/?h=i915-test-4.2.0-rc4

- Ted
-- next part --
A non-text attachment was scrubbed...
Name: dmesg.gz
Type: application/gzip
Size: 25784 bytes
Desc: not available
URL: 

-- next part --
A non-text attachment was scrubbed...
Name: config.gz
Type: application/gzip
Size: 31022 bytes
Desc: not available
URL: 

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
> I have 4 patches in git://people.freedesktop.org/~danvet/drm fixes-stuff
> but I couldn't test them yet since no dp mst here and I didn't find
> anything that would ship faster than 1-2 weeks yet. I'll try to get some
> other people here to test it meanwhile too.

I've tried pulling in your patches from fixes-stuff, onto Linus's tree
(without Linus's fix), and the good news is that I'm no longer
crashing on boot.

The *bad* news is that (a) it breaks the external monitor attached to
the docking station completely (this was working with Linus's patch),
and (b) it's triggering a LOCKDEP failure.

So even though Linus's patch wasn't supposed to work, I think I'm
going to back to it

- Ted


Jul 30 11:46:49 closure kernel: [4.221951] 
Jul 30 11:46:49 closure kernel: [4.221954] 
==
Jul 30 11:46:49 closure kernel: [4.221957] [ INFO: possible circular 
locking dependency detected ]
Jul 30 11:46:49 closure kernel: [4.221960] 4.2.0-rc4-13906-g5f1b75cd #16 
Not tainted
Jul 30 11:46:49 closure kernel: [4.221963] 
---
Jul 30 11:46:49 closure kernel: [4.221966] modprobe/503 is trying to 
acquire lock:
Jul 30 11:46:49 closure kernel: [4.221968]  (init_mutex){+.+.+.}, at: 
[] acpi_video_get_backlight_type+0x17/0x164
Jul 30 11:46:49 closure kernel: [4.221977] 
Jul 30 11:46:49 closure kernel: [4.221977] but task is already holding lock:
Jul 30 11:46:49 closure kernel: [4.221979]  
(&(&backlight_notifier)->rwsem){..}, at: [] 
__blocking_notifier_call_chain+0x37/0x69
Jul 30 11:46:49 closure kernel: [4.221987] 
Jul 30 11:46:49 closure kernel: [4.221987] which lock already depends on 
the new lock.
Jul 30 11:46:49 closure kernel: [4.221987] 
Jul 30 11:46:49 closure kernel: [4.221990] 
Jul 30 11:46:49 closure kernel: [4.221990] the existing dependency chain 
(in reverse order) is:
Jul 30 11:46:49 closure kernel: [4.221995] 
Jul 30 11:46:49 closure kernel: [4.221995] -> #1 
(&(&backlight_notifier)->rwsem){..}:
Jul 30 11:46:49 closure kernel: [4.222001][] 
lock_acquire+0x104/0x18b
Jul 30 11:46:49 closure kernel: [4.222007][] 
down_write+0x46/0x8a
Jul 30 11:46:49 closure kernel: [4.222012][] 
blocking_notifier_chain_register+0x36/0x57
Jul 30 11:46:49 closure kernel: [4.222017][] 
backlight_register_notifier+0x18/0x1a
Jul 30 11:46:49 closure kernel: [4.222022][] 
acpi_video_get_backlight_type+0xfa/0x164
Jul 30 11:46:49 closure kernel: [4.222028][] 
0xc03a1e45
Jul 30 11:46:49 closure audispd: No plugins found, exiting
Jul 30 11:46:49 closure kernel: [4.222032][] 
0xc03a28a8
Jul 30 11:46:49 closure kernel: [4.222036][] 
do_one_initcall+0x19a/0x1af
Jul 30 11:46:49 closure kernel: [4.222042][] 
do_init_module+0x60/0x1e3
Jul 30 11:46:49 closure kernel: [4.222047][] 
load_module+0x1c42/0x2059
Jul 30 11:46:49 closure kernel: [4.222052][] 
SyS_finit_module+0x85/0x92
Jul 30 11:46:49 closure kernel: [4.222056][] 
entry_SYSCALL_64_fastpath+0x16/0x73
Jul 30 11:46:49 closure kernel: [4.222060] 
Jul 30 11:46:49 closure kernel: [4.222060] -> #0 (init_mutex){+.+.+.}:
Jul 30 11:46:49 closure kernel: [4.222065][] 
__lock_acquire+0xc55/0xf54
Jul 30 11:46:49 closure kernel: [4.222070][] 
lock_acquire+0x104/0x18b
Jul 30 11:46:49 closure kernel: [4.222074][] 
mutex_lock_nested+0x70/0x391
Jul 30 11:46:49 closure kernel: [4.222078][] 
acpi_video_get_backlight_type+0x17/0x164
Jul 30 11:46:49 closure kernel: [4.222083][] 
acpi_video_backlight_notify+0x19/0x2f
Jul 30 11:46:49 closure kernel: [4.222088][] 
notifier_call_chain+0x4c/0x71
Jul 30 11:46:49 closure kernel: [4.222092][] 
__blocking_notifier_call_chain+0x50/0x69
Jul 30 11:46:49 closure kernel: [4.222098][] 
blocking_notifier_call_chain+0x14/0x16
Jul 30 11:46:49 closure kernel: [4.222103][] 
backlight_device_register+0x1df/0x1f1
Jul 30 11:46:49 closure kernel: [4.222108][] 
intel_backlight_register+0xf0/0x157 [i915]
Jul 30 11:46:49 closure kernel: [4.222146][] 
intel_modeset_gem_init+0x158/0x164 [i915]
Jul 30 11:46:49 closure kernel: [4.222176][] 
i915_driver_load+0xf1c/0x1139 [i915]
Jul 30 11:46:49 closure kernel: [4.05][] 
drm_dev_register+0x84/0xfd [drm]
Jul 30 11:46:49 closure kernel: [4.17][] 
drm_get_pci_dev+0x102/0x1bc [drm]
Jul 30 11:46:49 closure kernel: [4.28][] 
i915_pci_probe+0x4f/0x51 [i915]
Jul 30 11:46:49 closure kernel: [4.47][] 
pci_device_probe+0x74/0xd6
Jul 30 11:46:49 closure kernel: [4.53][] 
driver_probe_device+

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Thu, Jul 30, 2015 at 04:40:02PM +0200, Daniel Vetter wrote:
> On Wed, Jul 29, 2015 at 10:18:16PM -0700, Linus Torvalds wrote:
> >  drivers/gpu/drm/drm_atomic_helper.c | 8 +---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
> > b/drivers/gpu/drm/drm_atomic_helper.c
> > index 5b59d5ad7d1c..aac212297b49 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state 
> > *state, int conn_idx)
> > }
> >  
> > connector_state->best_encoder = new_encoder;
> > -   idx = drm_crtc_index(connector_state->crtc);
> > +   if (connector_state->crtc) {
> > +   idx = drm_crtc_index(connector_state->crtc);
> >  
> > -   crtc_state = state->crtc_states[idx];
> > -   crtc_state->mode_changed = true;
> > +   crtc_state = state->crtc_states[idx];
> > +   crtc_state->mode_changed = true;
> > +   }
> 
> This shouldn't happen since if it does we ended up stealing the encoder
> from the connector itself (we do check for connector_state->crtc earlier)
> and that would be a bug. I haven't figured out a precise theory but my
> guess is on the best_encoder selection, and indeed dp mst encoder
> selection seems to have gone belly up in 4.2 with the bisected commit.

Well, I just tested Linus's patch and it works.

BTW, is there any chance that I can suspend my laptop, and then move
it from my docking station at home (where I have a Dell 30" display)
to my docking station at work (where I have a Dell 24" display), and
actually have the new monitor be detected?  For at least the past
year, I have to reboot in order to be able to use the external
monitor?  This used to work, but it's been a very long-standing
regression.  I undrstand that Multi-stream DP is a evil horrible hack,
and supporting it is painful, but this used to work, and it hasn't in
a long time.  :-(

- Ted

[Intel-gfx] [REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Linus Torvalds]

On Thu, Jul 30, 2015 at 8:57 AM, Takashi Iwai  wrote:
> On Thu, 30 Jul 2015 17:32:28 +0200,
> Theodore Ts'o wrote:
>>
>> BTW, is there any chance that I can suspend my laptop, and then move
>> it from my docking station at home (where I have a Dell 30" display)
>> to my docking station at work (where I have a Dell 24" display), and
>> actually have the new monitor be detected?  For at least the past
>> year, I have to reboot in order to be able to use the external
>> monitor?  This used to work, but it's been a very long-standing
>> regression.  I undrstand that Multi-stream DP is a evil horrible hack,
>> and supporting it is painful, but this used to work, and it hasn't in
>> a long time.  :-(
>
> Relevant with this?
>https://bugs.freedesktop.org/show_bug.cgi?id=89589
>
> I wanted to check this by myself, too, as the same bug was reported to
> openSUSE bugzilla, but I had no hardware showing it.

Hmm. That commit e7d6f7d70829 looks like it should still revert fairly
cleanly (just move the call to intel_dp_mst_resume() to before the
intel_modeset_setup_hw_state() call and locking).

Ted, worth checking out, even if that presumably ends up
re-introducing some WARN_ON's..

Linus

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Linus Torvalds]

On Wed, Jul 29, 2015 at 6:39 PM, Theodore Ts'o  wrote:
>
> It's here:  https://goo.gl/photos/xHjn2Z97JQEw6k2C9

You didn't catch enough of the code line to decode the code, but it's
early enough in drm_crtc_index() (just five bytes in) that it's almost
certainly the very first dereference, so it's almost guaranteed to be
that

   crtc->dev

access as part of list_for_each_entry(), with crtc being NULL. And
yes, "->dev" is the very first field, so the offset is zero too (while
the "->mode_config" list access would not be at offset zero).

And it looks like it is called from drm_atomic_helper_check_modeset():
the reason it has a question mark in the backtrace is because the
fault happens before the stack frame has even been set up.

There are multiple calls to "drm_crtc_index()" from that function, I
can't tell which one it is. Looking at the code generation I get, I
think it's because update_connector_routing() gets inlined, and that
one does several calls. Most of them look like this:

if (connector->state->crtc) {
idx = drm_crtc_index(connector->state->crtc);

ie they check that the crtc is non-NULL, but that last one does not:

connector_state->best_encoder = new_encoder;
idx = drm_crtc_index(connector_state->crtc);

crtc_state = state->crtc_states[idx];
crtc_state->mode_changed = true;

and I suspect the fix might be something like the attached. Totally
untested. Ted?

This whole "atomic modeset" series has been one royal fuck-up, guys.
We've had too many of these kinds of crap issues.

   Linus
-- next part --
 drivers/gpu/drm/drm_atomic_helper.c | 8 +---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
b/drivers/gpu/drm/drm_atomic_helper.c
index 5b59d5ad7d1c..aac212297b49 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -230,10 +230,12 @@ update_connector_routing(struct drm_atomic_state *state, 
int conn_idx)
}

connector_state->best_encoder = new_encoder;
-   idx = drm_crtc_index(connector_state->crtc);
+   if (connector_state->crtc) {
+   idx = drm_crtc_index(connector_state->crtc);

-   crtc_state = state->crtc_states[idx];
-   crtc_state->mode_changed = true;
+   crtc_state = state->crtc_states[idx];
+   crtc_state->mode_changed = true;
+   }

DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] using [ENCODER:%d:%s] on 
[CRTC:%d]\n",
 connector->base.id,

[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Richard Harman]

(long time lurker, first time poster)

This (because the dock has a DP MST hub built in) reminds me of this
crash w/ my W540 - which I think are pretty similar hardware:

https://bugzilla.redhat.com/show_bug.cgi?id=1180747

Not enough of a coder to really troubleshoot, but I've got a dock, a MST
hub, and I'm willing to compile & test patches.  I've mostly left the HW
... disused because I was disgusted that my W530 could drive four
displays at once, and the W540 appears incapable due to the Intel chip
only supporting 3 CRTCs.

How can I help?

On 07/29/15 21:39, Theodore Ts'o wrote:
> On Wed, Jul 29, 2015 at 08:49:37PM -0400, Theodore Ts'o wrote:
>> Unfortunately the failure causes a series of recursive faults and I
>> haven't been able to capture the stack trace, but on 4.2-rcX kernels,
>> I can reliably cause the system to crash if my T540p is booted with
>> the docking station attached.
>>
>> It will also crash if I boot the system first, and then insert the
>> laptop into the dockstation.
>>
>> Unfortunately, I can't get a stack trace because there are a huge
>> number of recursive/double faults, and the system dies so quickly that
>> nothing ends up in the log files.  If you really need a stack dump I
>> can try to rig something, but modern Laptops don't have serial
>> consoles any more, alas, so it's bit of a pain.
> The bad news is that I tried to use kdump to capture a crashdump and
> hopefully get more information, and kdump utterly wedged on the panic.
> The good news is because it wedged the system, I was able to get the
> console stackdump before it scrolled off due to a whole series of
> recursive oops messages.
>
> It's here:  https://goo.gl/photos/xHjn2Z97JQEw6k2C9
>
> Hopefully tihs is useful.  It's not obvious how to revert this change,
> since there were a large number of changes to i915 after this.  If
> someone could help me with a revert, I'd be happy to test it.
>
> Thanks,
>
>   - Ted
>   
>
>
>> I was able to bisect it down to this commit, however: 8c7b5ccb72987:
>> "drm/i915: Use atomic helpers for computing changed flags:"
>>
>> Is there any chance Intel could add a Lenovo Dockstation with a
>> Multistream DP output to part of your test hardware?  Unfortunately it
>> seems pretty common that I see regressions with my particular
>> hardware.  Maybe there aren't enough people using Thinkpads any more?  :-(
>>
>>- Ted
>>
>>
>> P.S.  The git bisect log
>>
>> git bisect start
>> # bad: [421d125c06c4be4c5005cb69840206bd09b71dd6] builddeb: sign the modules 
>> after splitting out the debuginfo files
>> git bisect bad 421d125c06c4be4c5005cb69840206bd09b71dd6
>> # good: [b953c0d234bc72e8489d3bf51a276c5c4ec85345] Linux 4.1
>> git bisect good b953c0d234bc72e8489d3bf51a276c5c4ec85345
>> # good: [aeaa2122af4e53f3bfd28e8f294557bb95af43fc] drm/i915/skl: Add the 
>> INIT power domain to the MISC I/O power well
>> git bisect good aeaa2122af4e53f3bfd28e8f294557bb95af43fc
>> # bad: [4d70f38a760ad2879d2ebd84001c92980180f630] drm/i915/bios: remove a 
>> redundant NULL pointer check
>> git bisect bad 4d70f38a760ad2879d2ebd84001c92980180f630
>> # bad: [27a1b688d9f1fa2abd14bfe6a8729a19fb3b1b25] drm/i915/bxt: Enable 
>> WaEnableYV12BugFixInHalfSliceChicken7 for Broxton
>> git bisect bad 27a1b688d9f1fa2abd14bfe6a8729a19fb3b1b25
>> # good: [4be0731786de10d0e9ae1d159504c83c6b052647] drm/i915: Add crtc states 
>> before calling compute_config()
>> git bisect good 4be0731786de10d0e9ae1d159504c83c6b052647
>> # good: [d5432a9d19b61ba6a2b3d88f3026e0ca60eb57a1] drm/i915: Stage new 
>> modeset state straight into atomic state
>> git bisect good d5432a9d19b61ba6a2b3d88f3026e0ca60eb57a1
>> # bad: [a821fc46bc7bb6d4cf9a5f8d2787fd70231c2c10] drm/i915: Swap atomic 
>> state in legacy modeset
>> git bisect bad a821fc46bc7bb6d4cf9a5f8d2787fd70231c2c10
>> # bad: [8c7b5ccb729870e606321b3703e2c2e698c49a95] drm/i915: Use atomic 
>> helpers for computing changed flags
>> git bisect bad 8c7b5ccb729870e606321b3703e2c2e698c49a95
>> # good: [0f63cca2afdc38877e86acfa9821020f6e2213fd] drm/i915: Update crtc 
>> state active flag based on DPMS
>> git bisect good 0f63cca2afdc38877e86acfa9821020f6e2213fd
>> # good: [840bfe953384a134c8639f2964d9b74bfa671e16] drm/atomic: Make 
>> mode_fixup() optional for check_modeset()
>> git bisect good 840bfe953384a134c8639f2964d9b74bfa671e16
>> # first bad commit: [8c7b5ccb729870e606321b3703e2c2e698c49a95] drm/i915: Use 
>> atomic helpers for computing changed flags
>>
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[REGRESSION] Re: i915 driver crashes on T540p if docking station attached

[Theodore Ts'o]

On Wed, Jul 29, 2015 at 08:49:37PM -0400, Theodore Ts'o wrote:
> 
> Unfortunately the failure causes a series of recursive faults and I
> haven't been able to capture the stack trace, but on 4.2-rcX kernels,
> I can reliably cause the system to crash if my T540p is booted with
> the docking station attached.
> 
> It will also crash if I boot the system first, and then insert the
> laptop into the dockstation.
> 
> Unfortunately, I can't get a stack trace because there are a huge
> number of recursive/double faults, and the system dies so quickly that
> nothing ends up in the log files.  If you really need a stack dump I
> can try to rig something, but modern Laptops don't have serial
> consoles any more, alas, so it's bit of a pain.

The bad news is that I tried to use kdump to capture a crashdump and
hopefully get more information, and kdump utterly wedged on the panic.
The good news is because it wedged the system, I was able to get the
console stackdump before it scrolled off due to a whole series of
recursive oops messages.

It's here:  https://goo.gl/photos/xHjn2Z97JQEw6k2C9

Hopefully tihs is useful.  It's not obvious how to revert this change,
since there were a large number of changes to i915 after this.  If
someone could help me with a revert, I'd be happy to test it.

Thanks,

- Ted



> 
> I was able to bisect it down to this commit, however: 8c7b5ccb72987:
> "drm/i915: Use atomic helpers for computing changed flags:"
> 
> Is there any chance Intel could add a Lenovo Dockstation with a
> Multistream DP output to part of your test hardware?  Unfortunately it
> seems pretty common that I see regressions with my particular
> hardware.  Maybe there aren't enough people using Thinkpads any more?  :-(
> 
> - Ted
> 
> 
> P.S.  The git bisect log
> 
> git bisect start
> # bad: [421d125c06c4be4c5005cb69840206bd09b71dd6] builddeb: sign the modules 
> after splitting out the debuginfo files
> git bisect bad 421d125c06c4be4c5005cb69840206bd09b71dd6
> # good: [b953c0d234bc72e8489d3bf51a276c5c4ec85345] Linux 4.1
> git bisect good b953c0d234bc72e8489d3bf51a276c5c4ec85345
> # good: [aeaa2122af4e53f3bfd28e8f294557bb95af43fc] drm/i915/skl: Add the INIT 
> power domain to the MISC I/O power well
> git bisect good aeaa2122af4e53f3bfd28e8f294557bb95af43fc
> # bad: [4d70f38a760ad2879d2ebd84001c92980180f630] drm/i915/bios: remove a 
> redundant NULL pointer check
> git bisect bad 4d70f38a760ad2879d2ebd84001c92980180f630
> # bad: [27a1b688d9f1fa2abd14bfe6a8729a19fb3b1b25] drm/i915/bxt: Enable 
> WaEnableYV12BugFixInHalfSliceChicken7 for Broxton
> git bisect bad 27a1b688d9f1fa2abd14bfe6a8729a19fb3b1b25
> # good: [4be0731786de10d0e9ae1d159504c83c6b052647] drm/i915: Add crtc states 
> before calling compute_config()
> git bisect good 4be0731786de10d0e9ae1d159504c83c6b052647
> # good: [d5432a9d19b61ba6a2b3d88f3026e0ca60eb57a1] drm/i915: Stage new 
> modeset state straight into atomic state
> git bisect good d5432a9d19b61ba6a2b3d88f3026e0ca60eb57a1
> # bad: [a821fc46bc7bb6d4cf9a5f8d2787fd70231c2c10] drm/i915: Swap atomic state 
> in legacy modeset
> git bisect bad a821fc46bc7bb6d4cf9a5f8d2787fd70231c2c10
> # bad: [8c7b5ccb729870e606321b3703e2c2e698c49a95] drm/i915: Use atomic 
> helpers for computing changed flags
> git bisect bad 8c7b5ccb729870e606321b3703e2c2e698c49a95
> # good: [0f63cca2afdc38877e86acfa9821020f6e2213fd] drm/i915: Update crtc 
> state active flag based on DPMS
> git bisect good 0f63cca2afdc38877e86acfa9821020f6e2213fd
> # good: [840bfe953384a134c8639f2964d9b74bfa671e16] drm/atomic: Make 
> mode_fixup() optional for check_modeset()
> git bisect good 840bfe953384a134c8639f2964d9b74bfa671e16
> # first bad commit: [8c7b5ccb729870e606321b3703e2c2e698c49a95] drm/i915: Use 
> atomic helpers for computing changed flags
>