[Bug 66516] [845g regression] No output on LVDS

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=66516

--- Comment #3 from Chris Wilson <chris at chris-wilson.co.uk> ---
b5ea2d5681522f1b8ef886b5ac039903bf1d39fe is the first bad commit
commit b5ea2d5681522f1b8ef886b5ac039903bf1d39fe
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Jun 27 17:52:15 2013 +0200

    drm/i915: fix hpd interrupt register locking

    Our interrupt handler (in hardirq context) could race with the timer
    (in softirq context), hence we need to hold the spinlock around the
    call to ->hdp_irq_setup in intel_hpd_irq_handler, too.

    But as an optimization (and more so to clarify things) we don't need
    to do the irqsave/restore dance in the hardirq context.

    Note also that on ilk+ the race isn't just against the hotplug
    reenable timer, but also against the fifo underrun reporting. That one
    also modifies the SDEIMR register (again protected by the same
    dev_priv->irq_lock).

    To lock things down again sprinkle a assert_spin_locked. But exclude
    the functions touching SDEIMR for now, I want to extract them all into
    a new helper function (like we do already for pipestate, display
    interrupts and all the various gt interrupts).

    v2: Add the missing 't' Egbert spotted in a comment.

    v3: Actually fix the right misspelled comment (Paulo).

    Cc: Egbert Eich <eich at suse.de>
    Reviewed-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

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