drm/i915: wait for IPS_ENABLE when enabling IPS
authorPaulo Zanoni <paulo.r.zanoni@intel.com>
Thu, 19 Sep 2013 20:03:06 +0000 (17:03 -0300)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Thu, 10 Oct 2013 10:47:11 +0000 (12:47 +0200)
commit5ade2c2f5813733f23bbb2f21e8ba5c3f8474a2b
tree634cd7d8f67829cde94970318d270501c4684eab
parent076e29f225bb7a5d97fa95b78b8dca61599b4198
drm/i915: wait for IPS_ENABLE when enabling IPS

At the end of haswell_crtc_enable we have an intel_wait_for_vblank
with a big comment, and the message suggests it's a workaround for
something we don't really understand. So I removed that wait and
started getting HW state readout error messages saying that the IPS
state is not what we expected.

I investigated and concluded that after you write IPS_ENABLE to
IPS_CTL, the bit will only actually become 1 on the next vblank. So
add code to wait for the IPS_ENABLE bit. We don't really need this
wait right now due to the wait I already mentioned, but at least this
one has a reason to be there, while the other one is just to
workaround some problem: we may remove it in the future.

The wait also acts as a POSTING_READ which we missed.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/intel_display.c