drm/i915: Prevent double dpms on

Arguably this is a bug in drm-core in that we should not be called twice
in succession with DPMS_ON, however this is still occuring and we see
FDI link training failures on the second call leading to the occassional
blank display. For the time being ignore the repeated call.

Original patch by Dave Airlie <airlied@redhat.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index cf8d5e5a286e410a18239fb680ccf0edf80ca821..40cc5da264a9bdf5520909ba39ca2cb21c1ca5ca 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2370,6 +2370,9 @@ static void intel_crtc_dpms(struct drm_crtc *crtc, int mode)
        int pipe = intel_crtc->pipe;
        bool enabled;
 
+       if (intel_crtc->dpms_mode == mode)
+               return;
+
        intel_crtc->dpms_mode = mode;
        intel_crtc->cursor_on = mode == DRM_MODE_DPMS_ON;
 
@@ -5164,7 +5167,7 @@ static void intel_crtc_init(struct drm_device *dev, int pipe)
        dev_priv->pipe_to_crtc_mapping[intel_crtc->pipe] = &intel_crtc->base;
 
        intel_crtc->cursor_addr = 0;
-       intel_crtc->dpms_mode = DRM_MODE_DPMS_OFF;
+       intel_crtc->dpms_mode = -1;
        drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
 
        intel_crtc->busy = false;