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

[Jani Nikula <jani.nikula@linux.intel.com>]

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?

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
>
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-- 
Jani Nikula, Intel Open Source Technology Center
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