[Bug 98690] [SKL bisected] System freeze when starting X using kernel 4.9-rc1 or later

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=98690

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[i915][SKL] System freeze   |[SKL bisected] System
                   |when starting X using       |freeze when starting X
                   |kernel 4.9-rc1 or later     |using kernel 4.9-rc1 or
                   |                            |later

--- Comment #6 from Chris Wilson <chris at chris-wilson.co.uk> ---
Bisect result:

commit 339fd36238dd3494bc4617d181e7a37922c29ee9
Author: Peter Ujfalusi <peter.ujfalusi at ti.com>
Date:   Wed Aug 31 14:09:05 2016 +0300

    drm: drm_probe_helper: Fix output_poll_work scheduling

    drm_kms_helper_poll_enable_locked() should check if we have delayed event
    pending and if we have, schedule the work to run without delay.

    Currently the output_poll_work is only scheduled if any of the connectors
    have DRM_CONNECTOR_POLL_CONNECT or DRM_CONNECTOR_POLL_DISCONNECT with
    DRM_OUTPUT_POLL_PERIOD delay. It does not matter if we have delayed event
    already registered to be handled. The detection will be delayd by
    DRM_OUTPUT_POLL_PERIOD in any case.
    Furthermore if none of the connectors are marked as POLL_CONNECT or
    POLL_DISCONNECT because all connectors are either POLL_HPD or they are
    always connected: the output_poll_work will not run at all even if we
    have delayed event marked.

    When none of the connectors require polling, their initial status change
    from unknown to connected/disconnected is not going to be handled until
    the first kms application starts or if we have fb console enabled.

    Note that in general the output poll work should be enabled already
    when this happens, but at driver load usually the first probe happens
    before the output polling is enabled. This patch fixes this case.

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