i915: ensure that VGA plane is disabled

commit 0fde901f1ddd2ce0e380a6444f1fb7ca555859e9 upstream.

Some broken systems (like HP nc6120) in some cases, usually after LID
close/open, enable VGA plane, making display unusable (black screen on LVDS,
some strange mode on VGA output). We used to disable VGA plane only once at
startup. Now we also check, if VGA plane is still disabled while changing
mode, and fix that if something changed it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=57434
Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6294a41c513d64ce2965fdb19ddc087ddafd567b..4d3c7c6901be2163e603e257d51ac308b2f4a4b5 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8248,6 +8248,23 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
         * the crtc fixup. */
 }
 
+static void i915_redisable_vga(struct drm_device *dev)
+{
+       struct drm_i915_private *dev_priv = dev->dev_private;
+       u32 vga_reg;
+
+       if (HAS_PCH_SPLIT(dev))
+               vga_reg = CPU_VGACNTRL;
+       else
+               vga_reg = VGACNTRL;
+
+       if (I915_READ(vga_reg) != VGA_DISP_DISABLE) {
+               DRM_DEBUG_KMS("Something enabled VGA plane, disabling it\n");
+               I915_WRITE(vga_reg, VGA_DISP_DISABLE);
+               POSTING_READ(vga_reg);
+       }
+}
+
 /* Scan out the current hw modeset state, sanitizes it and maps it into the drm
  * and i915 state tracking structures. */
 void intel_modeset_setup_hw_state(struct drm_device *dev,
@@ -8328,6 +8345,8 @@ void intel_modeset_setup_hw_state(struct drm_device *dev,
                        intel_set_mode(&crtc->base, &crtc->base.mode,
                                       crtc->base.x, crtc->base.y, crtc->base.fb);
                }
+
+               i915_redisable_vga(dev);
        } else {
                intel_modeset_update_staged_output_state(dev);
        }