drm/i915: change CRTC assertion on LCPLL disable
drm/i915: change CRTC assertion on LCPLL disable

Currently, PC8 is enabled at modeset_global_resources, which is called
after intel_modeset_update_state. Due to this, there's a small race
condition on the case where we start enabling PC8, then do a modeset
while PC8 is still being enabled. The racing condition triggers a WARN
because intel_modeset_update_state will mark the CRTC as enabled, then
the thread that's still enabling PC8 might look at the data structure
and think that PC8 is being enabled while a pipe is enabled. Despite
the WARN, this is not really a bug since we'll wait for the
PC8-enabling thread to finish when we call modeset_global_resources.

The spec says the CRTC cannot be enabled when we disable LCPLL, so we
had a check for crtc->base.enabled. If we change to crtc->active we
will still prevent disabling LCPLL while the CRTC is enabled, and we
will also prevent the WARN above.

This is a replacement for the previous patch named
    "drm/i915: get/put PC8 when we get/put a CRTC"

Testcase: igt/pm_pc8/modeset-lpsp-stress-no-wait
Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>
(cherry picked from commit 798183c54799fbe1e5a5bfabb3a8c0505ffd2149
from -next due to Dave's report.)
Reported-by: Dave Jones <d5ec0d24602845f6f4b6a35ef729998d1fba5507@redhat.com>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs