[ 14/82] drm/i915: wait for a vblank to pass after tv detect

Ben Hutchings
2012-06-08T05:24:42Z

From: Daniel Vetter <daniel.vetter@ffwll.ch>

commit bf2125e2f7e931b50a6c76ba0435ba001409ccbf upstream.

Otherwise the hw will get confused and result in a black screen.

This regression has been most likely introduce in

commit 974b93315b2213b74a42a87e8a9d4fc8c0dbe90c
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sun Sep 5 00:44:20 2010 +0100

drm/i915/tv: Poll for DAC state change

That commit replace the first msleep(20) with a busy-loop, but failed
to keep the 2nd msleep around. Later on we've replaced all these
msleep(20) by proper vblanks.

For reference also see the commit in xf86-video-intel:

commit 1142be53eb8d2ee8a9b60ace5d49f0ba27332275
Author: Jesse Barnes <jbarnes@hobbes.lan>
Date: Mon Jun 9 08:52:59 2008 -0700

Fix TV programming: add vblank wait after TV_CTL writes

Fxies FDO bug #14000; we need to wait for vblank after
writing TV_CTL or following "DPMS on" calls may not actually enable the output.

v2: As suggested by Chris Wilson, add a small comment to ensure that
no one accidentally removes this vblank wait again - there really
seems to be no sane explanation for why we need it, but it is
required.

Launchpad: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/763688
Reported-and-Tested-by: Robert Lowery <rglowery@exemail.com.au>
Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/gpu/drm/i915/intel_tv.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 3346612..475f6d4 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1194,6 +1194,11 @@ intel_tv_detect_type(struct intel_tv *intel_tv,

I915_WRITE(TV_DAC, save_tv_dac & ~TVDAC_STATE_CHG_EN);
I915_WRITE(TV_CTL, save_tv_ctl);
+ POSTING_READ(TV_CTL);
+
+ /* For unknown reasons the hw barfs if we don't do this vblank wait. */
+ intel_wait_for_vblank(intel_tv->base.base.dev,
+ to_intel_crtc(intel_tv->base.base.crtc)->pipe);

/* Restore interrupt config */
if (connector->polled & DRM_CONNECTOR_POLL_HPD) {