drm/i915/dp: Be paranoid in case we disable a DP before it is attached
drm/i915/dp: Be paranoid in case we disable a DP before it is attached

Given that the hardware may be left in a random condition by the BIOS,
it is conceivable that we then attempt to clear the DP_PIPEB_SELECT bit
without us ever enabling/attaching the DP encoder to a pipe. Thus
causing a NULL deference when we attempt to wait for a vblank on that
crtc.

Reported-and-tested-by: Bryan Christ <0de214a1c972a2850a437170edbd66b953184b35@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36314
Signed-off-by: Chris Wilson <711c73f64afdce07b7e38039a96d2224209e9a6c@chris-wilson.co.uk>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36456
Reported-and-tested-by: Bo Wang <c75a52acff06576e6e930ae592884d4f93017f65@intel.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@kernel.org
Signed-off-by: Keith Packard <fd7f967895e9f35e58ec8a62a847a54d7fa7275f@keithp.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas