Re: [Intel-gfx] [PATCH 0/4] Important MST fixes for 4.6

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, May 31, 2016 at 12:49:03PM -0400, Lyude wrote:
> Unfortunately we've never really made use of creating/destroying connectors
> on the fly like we have with MST, so 4.6 ended up showing a lot of various
> bugs with hotplugging MST displays, booting with MST displays, etc. Most of
> these bugs are very likely to panic the kernel, and a couple of them end up
> even doing out of bounds memory accesses causing all sorts of other issues.
> 
> The proper fix for these issues is Dave's connector lifetime patch series
> in 4.7-rc1[1], however backporting those patches would be too big of a fix
> to submit for stable. This patch series is a much smaller set of changes to
> workaround this issue.
> 
> As another note: the first two patches in this series are already upstream for
> 4.7-rc1, however since we have the connector ref lifetime patches in 4.7-rc1
> they don't fix any kernel panics there, only a few inconsistencies in
> i915/drm's code. They do however, fix kernel panics for 4.6 since connectors
> getting destroyed can make dev->mode_config.num_connector have a different
> value from fb_helper->connector_count.
> 
> [1]: 0552f7651bc233e5407ab06ba97a9d7c25e19580 in master

In case it's not clear: There's no way we're going to backport the
connector refcounting stuff from 4.7, way too risky. But we still need
some way to make current stable kernels happy, and the 2 small hacks (plus
2 backports) seem like an adequate solution.

Hence acked from my side for applying to all supported stable kernels.

Cheers, Daniel
> 
> Lyude (4):
>   drm/i915/fbdev: Fix num_connector references in
>     intel_fb_initial_config()
>   drm/fb_helper: Fix references to dev->mode_config.num_connector
>   drm/i915: Discard previous atomic state on resume if connectors change
>   drm/atomic: Verify connector->funcs != NULL when clearing states
> 
>  drivers/gpu/drm/drm_atomic.c         |  2 +-
>  drivers/gpu/drm/drm_fb_helper.c      |  5 ++---
>  drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
>  drivers/gpu/drm/i915/intel_fbdev.c   |  6 +++---
>  4 files changed, 18 insertions(+), 7 deletions(-)
> 
> -- 
> 2.5.5
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch