From 8577c319b6511fbc391f3775225fecd8b979bc26 Mon Sep 17 00:00:00 2001
From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date: Fri, 9 Nov 2018 16:09:23 +0200
Subject: drm/i915/icl: Drop spurious register read from icl_dbuf_slices_update
Git-commit: 8577c319b6511fbc391f3775225fecd8b979bc26
Patch-mainline: v5.0-rc1
References: bsc#1113956

Register DBUF_CTL_S2 is read and it's value is not used. As
there is no explanation why we should prime the hardware with
read, remove it as spurious.

Fixes: aa9664ffe863 ("drm/i915/icl: Enable 2nd DBuf slice only when needed")
Cc: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181109140924.2663-1-mika.kuoppala@linux.intel.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index f945db6ea420..770de2632530 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -3236,8 +3236,7 @@ static u8 intel_dbuf_max_slices(struct drm_i915_private *dev_priv)
 void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 			    u8 req_slices)
 {
-	u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
-	u32 val;
+	const u8 hw_enabled_slices = dev_priv->wm.skl_hw.ddb.enabled_slices;
 	bool ret;
 
 	if (req_slices > intel_dbuf_max_slices(dev_priv)) {
@@ -3248,7 +3247,6 @@ void icl_dbuf_slices_update(struct drm_i915_private *dev_priv,
 	if (req_slices == hw_enabled_slices || req_slices == 0)
 		return;
 
-	val = I915_READ(DBUF_CTL_S2);
 	if (req_slices > hw_enabled_slices)
 		ret = intel_dbuf_slice_set(dev_priv, DBUF_CTL_S2, true);
 	else
-- 
2.20.1