drm/i915: Turn on 945 self-refresh only if single CRTC is active

Enable self-refresh on 945 when just one CRTC is activated.
Otherwise user would get display flicker with dual display.

This fixes https://bugs.freedesktop.org/show_bug.cgi?id=27667

Signed-off-by: Li Peng <peng.li@intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a8d65b7cb72a..fdeff4353725 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4483,6 +4483,7 @@ static void intel_idle_update(struct work_struct *work)
         struct drm_device *dev = dev_priv->dev;
         struct drm_crtc *crtc;
         struct intel_crtc *intel_crtc;
+        int enabled = 0;
 
         if (!i915_powersave)
                 return;
@@ -4491,21 +4492,22 @@ static void intel_idle_update(struct work_struct *work)
 
         i915_update_gfx_val(dev_priv);
 
-        if (IS_I945G(dev) || IS_I945GM(dev)) {
-                DRM_DEBUG_DRIVER("enable memory self refresh on 945\n");
-                I915_WRITE(FW_BLC_SELF, FW_BLC_SELF_EN_MASK | FW_BLC_SELF_EN);
-        }
-
         list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
                 /* Skip inactive CRTCs */
                 if (!crtc->fb)
                         continue;
 
+                enabled++;
                 intel_crtc = to_intel_crtc(crtc);
                 if (!intel_crtc->busy)
                         intel_decrease_pllclock(crtc);
         }
 
+        if ((enabled == 1) && (IS_I945G(dev) || IS_I945GM(dev))) {
+                DRM_DEBUG_DRIVER("enable memory self refresh on 945\n");
+                I915_WRITE(FW_BLC_SELF, FW_BLC_SELF_EN_MASK | FW_BLC_SELF_EN);
+        }
+
         mutex_unlock(&dev->struct_mutex);
 }