From 9e532c331c378b6ba7a0886b8410bcb523663b28 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sun, 17 Apr 2011 06:38:35 +0100 Subject: drm/i915/dp: Be paranoid in case we disable a DP before it is attached commit 31acbcc408f412d1ba73765b846c38642be553c3 upstream. 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 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36314 Signed-off-by: Chris Wilson Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36456 Reported-and-tested-by: Bo Wang Signed-off-by: Keith Packard Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/i915/intel_dp.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'drivers/gpu/drm') diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 51cb4e36997..8f3a02bc1cf 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -1455,7 +1455,8 @@ intel_dp_link_down(struct intel_dp *intel_dp) if (!HAS_PCH_CPT(dev) && I915_READ(intel_dp->output_reg) & DP_PIPEB_SELECT) { - struct intel_crtc *intel_crtc = to_intel_crtc(intel_dp->base.base.crtc); + struct drm_crtc *crtc = intel_dp->base.base.crtc; + /* Hardware workaround: leaving our transcoder select * set to transcoder B while it's off will prevent the * corresponding HDMI output on transcoder A. @@ -1470,7 +1471,19 @@ intel_dp_link_down(struct intel_dp *intel_dp) /* Changes to enable or select take place the vblank * after being written. */ - intel_wait_for_vblank(dev, intel_crtc->pipe); + if (crtc == NULL) { + /* We can arrive here never having been attached + * to a CRTC, for instance, due to inheriting + * random state from the BIOS. + * + * If the pipe is not running, play safe and + * wait for the clocks to stabilise before + * continuing. + */ + POSTING_READ(intel_dp->output_reg); + msleep(50); + } else + intel_wait_for_vblank(dev, to_intel_crtc(crtc)->pipe); } I915_WRITE(intel_dp->output_reg, DP & ~DP_PORT_EN); -- cgit v1.2.3