[Intel-gfx] [PATCH] drm/i915: Skip fbdev core suspend/resume when fbdev emulation is disabled.

[Chris Wilson]

On Tue, Jun 28, 2016 at 09:51:34AM -0700, Bob Paauwe wrote:
> On Tue, 28 Jun 2016 16:47:28 +0100
> Chris Wilson <chris at chris-wilson.co.uk> wrote:
> 
> > On Tue, Jun 28, 2016 at 08:42:01AM -0700, Bob Paauwe wrote:
> > > When fbdev emulation is disabled it is not a good idea to call into
> > > the core fb_set_suspend() function as this will cause suspend and
> > > resume to fail. Also ifbdev->fb is null so the defeference farther
> > > down will oops. Nothing in that path is needed in this case so bail
> > > early when ifbdev->fb is null.  
> > 
> > This function does not exist when fbdev emulation is disabled. I suspect
> > you mean something else, so please give the evidence of the problem this
> > patch is addressing.
> > -Chris
> > 
> 
> Sorry, I probably should have been more explicit. This happens when you
> set "drm_kms_helper.fbdev_emulation=0" on the command line. In that
> case the function is called and will crash during a S3 suspend and
> probably during hibernation as well. 
> 
> You're right, it isn't applicable when the kernel config
> CONFIG_DRM_FBDEV_EMULATION is off.

Simply put, the bug is in drm_fb_helper_init().

Lots of drivers to review for their handling of errors from fbdev.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre