drm/i915: Assert the dbuf is enabled when disabling DC5/6

Like with cdclk, the DMC is supposed to manage dbuf enabling/disabling.
Let's make sure it has correctly restored the dbuf state to enabled
when we disable the DC states.

v2: s/skl/gen9/ in function name (Imre)

Cc: Imre Deak <imre.deak@intel.com>
Suggested-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463407180-28993-1-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Imre Deak <imre.deak@intel.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index a1741182f924..fe8faf30bda7 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -806,6 +806,15 @@ static bool gen9_dc_off_power_well_enabled(struct drm_i915_private *dev_priv,
         return (I915_READ(DC_STATE_EN) & DC_STATE_EN_UPTO_DC5_DC6_MASK) == 0;
 }
 
+static void gen9_assert_dbuf_enabled(struct drm_i915_private *dev_priv)
+{
+        u32 tmp = I915_READ(DBUF_CTL);
+
+        WARN((tmp & (DBUF_POWER_STATE | DBUF_POWER_REQUEST)) !=
+             (DBUF_POWER_STATE | DBUF_POWER_REQUEST),
+             "Unexpected DBuf power power state (0x%08x)\n", tmp);
+}
+
 static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
                                           struct i915_power_well *power_well)
 {
@@ -814,6 +823,8 @@ static void gen9_dc_off_power_well_enable(struct drm_i915_private *dev_priv,
         WARN_ON(dev_priv->cdclk_freq !=
                 dev_priv->display.get_display_clock_speed(dev_priv->dev));
 
+        gen9_assert_dbuf_enabled(dev_priv);
+
         if (IS_BROXTON(dev_priv))
                 broxton_ddi_phy_verify_state(dev_priv);
 }