drm/i915: check PPS regs for sanity when using eDP

If these regs don't have valid values, the panel won't come up, and may
even cause a system hang.  So do a basic sanity check when an eDP panel
is detected.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44305
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 110552ff302c..6346b29ee934 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -2462,6 +2462,13 @@ intel_dp_init(struct drm_device *dev, int output_reg)
                 pp_off = I915_READ(PCH_PP_OFF_DELAYS);
                 pp_div = I915_READ(PCH_PP_DIVISOR);
 
+                if (!pp_on || !pp_off || !pp_div) {
+                        DRM_INFO("bad panel power sequencing delays, disabling panel\n");
+                        intel_dp_encoder_destroy(&intel_dp->base.base);
+                        intel_dp_destroy(&intel_connector->base);
+                        return;
+                }
+
                 /* Pull timing values out of registers */
                 cur.t1_t3 = (pp_on & PANEL_POWER_UP_DELAY_MASK) >>
                         PANEL_POWER_UP_DELAY_SHIFT;