linux-kernel - Re: i865, drm_modeset_lock_all: BUG: unable to handle kernel NULL pointer dereference at 00000104

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Message-ID: <alpine.LRH.2.20.1608231433350.17020@math.ut.ee>
Date:   Tue, 23 Aug 2016 14:35:03 +0300 (EEST)
From:   Meelis Roos <mroos@...ux.ee>
To:     Chris Wilson <chris@...is-wilson.co.uk>
cc:     Linux Kernel list <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Subject: Re: i865, drm_modeset_lock_all: BUG: unable to handle kernel NULL
 pointer dereference at 00000104

> Looks like an incorrect call to drm_encoder_cleanup() from the error
> path. If we hit the error path we have never called drm_encoder_init.
> Please try:
> 
> diff --git a/drivers/gpu/drm/i915/intel_dvo.c b/drivers/gpu/drm/i915/intel_dvo.c
> index 47bdf9dad0d3..b9e5a63a7c9e 100644
> --- a/drivers/gpu/drm/i915/intel_dvo.c
> +++ b/drivers/gpu/drm/i915/intel_dvo.c
> @@ -554,7 +554,6 @@ void intel_dvo_init(struct drm_device *dev)
>  		return;
>  	}
>  
> -	drm_encoder_cleanup(&intel_encoder->base);
>  	kfree(intel_dvo);
>  	kfree(intel_connector);
>  }

It works - the BUG is gone.

Now I get just 
[drm:__intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* pipe A underrun

[   10.499523] agpgart-intel 0000:00:00.0: Intel 865 Chipset
[   10.499623] agpgart-intel 0000:00:00.0: detected gtt size: 131072K total, 131072K mappable
[   10.499928] agpgart-intel 0000:00:00.0: detected 16384K stolen memory
[   10.500939] [drm] Memory usable by graphics device = 128M
[   10.501029] [drm] Replacing VGA console driver
[   10.502804] Console: switching to colour dummy device 80x25
[   10.504746] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[   10.504760] [drm] Driver supports precise vblank timestamp query.
[   11.210224] vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
[   11.237197] [drm] RC6 disabled, disabling runtime PM support
[   11.237407] [drm] initialized overlay support
[   11.362560] [drm:__intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* pipe A underrun
[   11.418776] i915 0000:00:02.0: No connectors reported connected with modes
[   11.418792] [drm] Cannot find any crtc or sizes - going 1024x768
[   11.421148] fbcon: inteldrmfb (fb0) is primary device
[   11.448292] Console: switching to colour frame buffer device 128x48
[   11.458643] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device


-- 
Meelis Roos (mroos@...ux.ee)