[REGRESSION] v3.12-rc1: i915_driver_load oopses when sysfb enabled

David Herrmann dh.herrmann at gmail.com
Sat Sep 7 07:30:03 PDT 2013

Hi Tom

On Sat, Sep 7, 2013 at 3:52 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
> Hi
> On Sat, Sep 7, 2013 at 3:45 PM, Tom Gundersen <teg at jklm.no> wrote:
>> On Sat, Sep 7, 2013 at 2:40 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
>>> It seems to be unrelated to the x86-sysfb changes. The WARN_ON
>>> triggered here obviously means that i915 remaps VMEM before removing
>>> efifb. So either i915 now calls ioremap and friends _before_ calling
>>> remove_conflicting_framebuffers(), or efifb is not unloaded correctly.
>> I redid all the tests, and I'm now not able to reproduce this with
>> efifb, only with simplefb (not sure if I made a mistake before or if
>> some config changed). I attached the two different dmesg outputs (only
>> difference is X86_SYSFB).
>>> Tom, some things off the top of my head:
>>> - Is efifb still running after i915 loaded? You can see that via:
>>>   cat /sys/class/graphics/fb0/name
>>>   (and also fb1, fb2, ... whatever is there)
>>>   If it's not running, anymore, then it's quite likely an i915 issue.
>> I only have /sys/class/graphics/fb0/name and it says inteldrmfb (this
>> is after i915 has taken over from simplefb).
>>> - Do you get a "fb: conflicting hw usage ..." in your dmesg log?
>> Yes: "fb: conflicting fb hw usage inteldrmfb vs simple - removing
>> generic driver"
> Ok, now this makes sense. simplefb lacks the ->fb_destroy() callback
> so it does not correctly react to remove_conflicting_framebuffer().
> But you can safely ignore the warning as simplefb is still unloaded.
> So it cannot be accessed anymore. It just leaks the remapping.
> I will send a patch later today which adds the fb_destroy() callback.

Attached are two patches. The first one should fix this issue, the
second one is the rebased ioremap_wc() patch from the other thread.

Does this fix the issue (and the speed-problems)?

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