Re: [PATCH] drm/i915: Don't call intel_prepare_ddi when encoder list isn't yet initialized.

Jani Nikula
2015-09-28T08:08:10Z

On Fri, 25 Sep 2015, "Vivi, Rodrigo" <rodrigo.vivi@intel.com> wrote:
> On Fri, 2015-09-25 at 13:52 +0300, Jani Nikula wrote:
>> On Wed, 23 Sep 2015, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
>> > In case something goes wrong with power well initialization we were
>> > calling
>> > intel_prepare_ddi during boot while encoder list isnt't initilized.
>>
>> Broken record, is this a regression, what is the regressing commit,
>> or
>> if this was always broken, which commit introduced the broken
>> feature?
>
> I believe it is broken since this call was introduced, but when
> everything goes as expected it isn't executed.
> Only in rare cases where power well initialization didn't go well and
> post call is called during init it will trigger this case.
> I don't believe this is something that a regular user of stables
> platforms should worrie though... but it is always good to protect to
> be on the safe side.

Rodrigo, both Daniel and I asked which commit broke things. We have to
keep asking this again and again, like a broken record. It doesn't scale
that we have to dig the logs for every patch that looks like a fix, just
to decide where to queueu the patch.

This was the one:

commit 1d2b9526a790d55b7ae870934a74937081f62de2
Author: Damien Lespiau <damien.lespiau@intel.com>
Date: Fri Mar 6 18:50:53 2015 +0000

drm/i915/skl: Restore the DDI translation tables when enabling PW1

And the patch, amended with the reference, is now pushed to
drm-intel-fixes. Thanks for the patch and review.

BR,
Jani.

>
>>
>> BR,
>> Jani.
>>
>>
>> >
>> > [ 9.618747] i915 0000:00:02.0: Invalid ROM contents
>> > [ 9.631446] [drm] failed to find VBIOS tables
>> > [ 9.720036] BUG: unable to handle kernel NULL pointer
>> > dereference at 00000000
>> > 00000058
>> > [ 9.721986] IP: [<ffffffffa014eb72>]
>> > ddi_get_encoder_port+0x82/0x190 [i915]
>> > [ 9.723736] PGD 0
>> > [ 9.724286] Oops: 0000 [#1] PREEMPT SMP
>> > [ 9.725386] Modules linked in: intel_powerclamp snd_hda_intel(+)
>> > coretemp crc
>> > 32c_intel snd_hda_codec snd_hda_core serio_raw snd_pcm snd_timer
>> > i915(+) parport
>> > _pc parport pinctrl_sunrisepoint pinctrl_intel nfsd nfs_acl
>> > [ 9.730635] CPU: 0 PID: 497 Comm: systemd-udevd Not tainted
>> > 4.3.0-rc2-eywa-10
>> > 967-g72de2cfd-dirty #2
>> > [ 9.732785] Hardware name: Intel Corporation Cannonlake Client
>> > platform/Skyla
>> > ke DT DDR4 RVP8, BIOS CNLSE2R1.R00.X021.B00.1508040310 08/04/2015
>> > [ 9.735785] task: ffff88008a704700 ti: ffff88016a1ac000 task.ti:
>> > ffff88016a1a
>> > c000
>> > [ 9.737584] RIP: 0010:[<ffffffffa014eb72>] [<ffffffffa014eb72>]
>> > ddi_get_enco
>> > der_port+0x82/0x190 [i915]
>> > [ 9.739934] RSP: 0000:ffff88016a1af710 EFLAGS: 00010296
>> > [ 9.741184] RAX: 000000000000004e RBX: ffff88008a9edc98 RCX:
>> > 0000000000000001
>> > [ 9.742934] RDX: 000000000000004e RSI: ffffffff81fc1e82 RDI:
>> > 00000000ffffffff
>> > [ 9.744634] RBP: ffff88016a1af730 R08: 0000000000000000 R09:
>> > 0000000000000578
>> > [ 9.746333] R10: 0000000000001065 R11: 0000000000000578 R12:
>> > fffffffffffffff8
>> > [ 9.748033] R13: ffff88016a1af7a8 R14: ffff88016a1af794 R15:
>> > 0000000000000000
>> > [ 9.749733] FS: 00007eff2e1e07c0(0000)
>> > GS:ffff88016fc00000(0000) knlGS:00000
>> > 00000000000
>> > [ 9.751683] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> > [ 9.753083] CR2: 0000000000000058 CR3: 000000016922b000 CR4:
>> > 00000000003406f0
>> > [ 9.754782] Stack:
>> > [ 9.755332] ffff88008a9edc98 ffff88008a9ed800 ffffffffa01d07b0
>> > 00000000fffb9
>> > 09e
>> > [ 9.757232] ffff88016a1af7d8 ffffffffa0154ea7 0000000000000246
>> > ffff88016a370
>> > 080
>> > [ 9.759182] ffff88016a370080 ffff88008a9ed800 0000000000000246
>> > ffff88008a9ed
>> > c98
>> > [ 9.761132] Call Trace:
>> > [ 9.761782] [<ffffffffa0154ea7>] intel_prepare_ddi+0x67/0x860
>> > [i915]
>> > [ 9.763332] [<ffffffff81a56996>] ?
>> > _raw_spin_unlock_irqrestore+0x26/0x40
>> > [ 9.765031] [<ffffffffa00fad01>] ? gen9_read32+0x141/0x360
>> > [i915]
>> > [ 9.766531] [<ffffffffa00b43e1>] skl_set_power_well+0x431/0xa80
>> > [i915]
>> > [ 9.768181] [<ffffffffa00b4a63>]
>> > skl_power_well_enable+0x13/0x20 [i915]
>> > [ 9.769781] [<ffffffffa00b2188>]
>> > intel_power_well_enable+0x28/0x50 [i915]
>> > [ 9.771481] [<ffffffffa00b4d52>]
>> > intel_display_power_get+0x92/0xc0 [i915]
>> > [ 9.773180] [<ffffffffa00b4fcb>]
>> > intel_display_set_init_power+0x3b/0x40 [i91
>> > 5]
>> > [ 9.774980] [<ffffffffa00b5170>]
>> > intel_power_domains_init_hw+0x120/0x520 [i9
>> > 15]
>> > [ 9.776780] [<ffffffffa0194c61>] i915_driver_load+0xb21/0xf40
>> > [i915]
>> >
>> > So let's protect this case.
>> >
>> > My first attempt was to remove the intel_prepare_ddi, but Daniel
>> > had pointed out
>> > this is really needed to restore those registers values. And Imre
>> > pointed out
>> > that this case was without the flag protection and this was
>> > actually where things
>> > were going bad. So I've just checked and this indeed solves my
>> > issue.
>> >
>> > Cc: Imre Deak <imre.deak@intel.com>
>> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> > ---
>> > drivers/gpu/drm/i915/intel_runtime_pm.c | 3 ++-
>> > 1 file changed, 2 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c
>> > b/drivers/gpu/drm/i915/intel_runtime_pm.c
>> > index 85c35fd..d194492 100644
>> > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
>> > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
>> > @@ -246,7 +246,8 @@ static void skl_power_well_post_enable(struct
>> > drm_i915_private *dev_priv,
>> > }
>> >
>> > if (power_well->data == SKL_DISP_PW_1) {
>> > - intel_prepare_ddi(dev);
>> > + if (!dev_priv->power_domains.initializing)
>> > + intel_prepare_ddi(dev);
>> > gen8_irq_power_well_post_enable(dev_priv, 1 <<
>> > PIPE_A);
>> > }
>> > }
>> > --
>> > 2.4.3
>> >
>> > _______________________________________________
>> > Intel-gfx mailing list
>> > Intel-gfx@lists.freedesktop.org
>> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>

--
Jani Nikula, Intel Open Source Technology Center