Re: [PATCH] drm/i915: Stop calling intel_prepare_ddi during power well initialization.

Imre Deak
2015-09-23T17:48:34Z

On ke, 2015-09-23 at 17:34 +0000, Vivi, Rodrigo wrote:
> here goes one trace...
> To be honest I'm confused as well: looking to the code that initializing boolean should be protecting this case...
> And if I remove this first one it will end up on that other at post enable...

It is the one in skl_power_well_post_enable(), since that doesn't check
for the flag.

>
> But apparently this only happens when something didn't go well with power well initialization...
>
> so, besides the initialization and resume from s3 this path here happens on every wake up from DC5/DC6?
>
> [ 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]
>
>
> ________________________________________
> From: Daniel Vetter [daniel.vetter@ffwll.ch] on behalf of Daniel Vetter [daniel@ffwll.ch]
> Sent: Wednesday, September 23, 2015 8:58 AM
> To: Vivi, Rodrigo
> Cc: intel-gfx@lists.freedesktop.org; Shah, Suketu J
> Subject: Re: [Intel-gfx] [PATCH] drm/i915: Stop calling intel_prepare_ddi during power well initialization.
>
> On Tue, Sep 22, 2015 at 08:03:59AM -0700, Rodrigo Vivi wrote:
> > The comment removed along with the calls explains why they shouldn't be here:
> >
> > /* DDI buffer programming unnecessary during driver-load/resume
> > * as it's already done during modeset initialization then.
> > * It's also invalid here as encoder list is still uninitialized.
> > */
> >
> > And the protection is not working well causing issues during the boot where
> > power well initialization doesn't go as expected.
> >
> > So this call during modeset initialization where the encoder list is yet
> > unitilized causes a NULL dereference breaking i915.
> >
> > While we don't find the right protection and we don't understand why this is
> > actually needed I believe it is safe to just remove these calls.
> >
> > Cc: Suketu Shah <suketu.j.shah@intel.com>
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
>
> But if we shut down the power well the hw will forget these values. Where
> are they programmed now? Which commit broke this, how does this blow up?
> Please add more details, atm I have no idea what to do with this patch but
> be confused about it ...
> -Daniel
>
> > ---
> > drivers/gpu/drm/i915/intel_runtime_pm.c | 8 --------
> > 1 file changed, 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > index 85c35fd..f7027ea 100644
> > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > @@ -246,7 +246,6 @@ 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);
> > gen8_irq_power_well_post_enable(dev_priv, 1 << PIPE_A);
> > }
> > }
> > @@ -632,13 +631,6 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
> > power_well->data == SKL_DISP_PW_2) {
> > if (SKL_ENABLE_DC6(dev)) {
> > skl_disable_dc6(dev_priv);
> > - /*
> > - * DDI buffer programming unnecessary during driver-load/resume
> > - * as it's already done during modeset initialization then.
> > - * It's also invalid here as encoder list is still uninitialized.
> > - */
> > - if (!dev_priv->power_domains.initializing)
> > - intel_prepare_ddi(dev);
> > } else {
> > gen9_disable_dc5(dev_priv);
> > }
> > --
> > 2.4.3
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx