[PATCH xserver] modesetting: re-set the crtc's mode when link-status goes BAD

[Martin Peres]

On 11/04/17 04:47, Eric Anholt wrote:
> Martin Peres <martin.peres at linux.intel.com> writes:
>
>> Despite all the careful planing of the kernel, a link may become
>> insufficient to handle the currently-set mode. At this point, the
>> kernel should mark this particular configuration as being broken
>> and potentially prune the mode before setting the offending connector's
>> link-status to BAD and send the userspace a hotplug event. This may
>> happen right after a modeset or later on.
>>
>> Upon receiving a hot-plug event, we iterate through the connectors to
>> re-apply the currently-set mode on all the connectors that have a
>> link-status property set to BAD. This modeset may fail immediatly if
>> the kernel has already pruned the mode we are trying to set but it
>> does not matter as -modesetting has no business picking another
>> mode if the modeset did fail. To make users aware of this problem
>
> I think I'd like to replace the "This modeset" sentence with "The kernel
> may be able to get the link to work by dropping to using a lower link
> bpp (with the same display bpp).  However, the modeset may fail if the
> kernel has pruned the mode, so to make users aware..."  Does that sound
> good to you?

Yep, nice improvement. Thanks!

>
> I'll give this patch a day or two for anyone else to complain, then I'll
> push.
>
>> a warning is outputed in the logs to warn about having a
>> potentially-black display.
>>
>> This patch does not modify the current behaviour of always propagating
>> the events to the randr clients. This allows desktop environments to
>> re-probe the connectors and select a new resolution based on the new
>> (currated) mode list if a mode disapeared. This behaviour is expected in
>> order to pass the Display Port compliance tests.
>>
>> Signed-off-by: Martin Peres <martin.peres at linux.intel.com>
>
>
>
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