[PATCH v1 1/2] drm/i915: Ensure no conflicts with BIOS when updating Dbuf

[Stanislav Lisovskiy]

TGL BIOS seems to enable both DBuf slices ocasionally, depending
how many displays are connected, while i915 according to BSpec
was powering on S1 DBuf slice, until a modeset was done.

This was causing a brief flash during the boot as we were
disabling slice, previously used by BIOS with that.

To prevent this, now we are ensuring tht we are enabling
_at least_ one slice, but if there are more, let's not
power them off.

Fixes: ff2cd8635e41 ("drm/i915: Correctly map DBUF slices to pipes")
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_power.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
index 53056def5414..b9a9cbad8a03 100644
--- a/drivers/gpu/drm/i915/display/intel_display_power.c
+++ b/drivers/gpu/drm/i915/display/intel_display_power.c
@@ -4470,11 +4470,13 @@ void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 
 static void icl_dbuf_enable(struct drm_i915_private *dev_priv)
 {
+	skl_ddb_get_hw_state(dev_priv);
 	/*
-	 * Just power up 1 slice, we will
+	 * Just power up at least 1 slice, we will
 	 * figure out later which slices we have and what we need.
 	 */
-	icl_dbuf_slices_update(dev_priv, BIT(DBUF_S1));
+	icl_dbuf_slices_update(dev_priv, dev_priv->enabled_dbuf_slices_mask |
+			       BIT(DBUF_S1));
 }
 
 static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
-- 
2.24.1.485.gad05a3d8e5