video: exynos_dp: add bit-masking for LINK_TRAINING_CTL register

This patch adds bit-masking for LINK_TRAINING_CTL register, when
pre-emphasis level is set. The bit 3 and bit 2 of LINK_TRAINING_CTL
register are used for pre-emphasis level setting, so other bits
should be masked.
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/exynos/exynos_dp_reg.c

@@ -895,7 +895,9 @@ void exynos_dp_set_lane0_pre_emphasis(struct exynos_dp_device *dp, u32 level)
 {
 	u32 reg;
 
-	reg = level << PRE_EMPHASIS_SET_SHIFT;
+	reg = readl(dp->reg_base + EXYNOS_DP_LN0_LINK_TRAINING_CTL);
+	reg &= ~PRE_EMPHASIS_SET_MASK;
+	reg |= level << PRE_EMPHASIS_SET_SHIFT;
 	writel(reg, dp->reg_base + EXYNOS_DP_LN0_LINK_TRAINING_CTL);
 }
 
@@ -903,7 +905,9 @@ void exynos_dp_set_lane1_pre_emphasis(struct exynos_dp_device *dp, u32 level)
 {
 	u32 reg;
 
-	reg = level << PRE_EMPHASIS_SET_SHIFT;
+	reg = readl(dp->reg_base + EXYNOS_DP_LN1_LINK_TRAINING_CTL);
+	reg &= ~PRE_EMPHASIS_SET_MASK;
+	reg |= level << PRE_EMPHASIS_SET_SHIFT;
 	writel(reg, dp->reg_base + EXYNOS_DP_LN1_LINK_TRAINING_CTL);
 }
 
@@ -911,7 +915,9 @@ void exynos_dp_set_lane2_pre_emphasis(struct exynos_dp_device *dp, u32 level)
 {
 	u32 reg;
 
-	reg = level << PRE_EMPHASIS_SET_SHIFT;
+	reg = readl(dp->reg_base + EXYNOS_DP_LN2_LINK_TRAINING_CTL);
+	reg &= ~PRE_EMPHASIS_SET_MASK;
+	reg |= level << PRE_EMPHASIS_SET_SHIFT;
 	writel(reg, dp->reg_base + EXYNOS_DP_LN2_LINK_TRAINING_CTL);
 }
 
@@ -919,7 +925,9 @@ void exynos_dp_set_lane3_pre_emphasis(struct exynos_dp_device *dp, u32 level)
 {
 	u32 reg;
 
-	reg = level << PRE_EMPHASIS_SET_SHIFT;
+	reg = readl(dp->reg_base + EXYNOS_DP_LN3_LINK_TRAINING_CTL);
+	reg &= ~PRE_EMPHASIS_SET_MASK;
+	reg |= level << PRE_EMPHASIS_SET_SHIFT;
 	writel(reg, dp->reg_base + EXYNOS_DP_LN3_LINK_TRAINING_CTL);
 }
 

drivers/video/exynos/exynos_dp_reg.h

@@ -285,6 +285,7 @@
 #define SW_TRAINING_PATTERN_SET_NORMAL		(0x0 << 0)
 
 /* EXYNOS_DP_LN0_LINK_TRAINING_CTL */
+#define PRE_EMPHASIS_SET_MASK			(0x3 << 3)
 #define PRE_EMPHASIS_SET_SHIFT			(3)
 
 /* EXYNOS_DP_DEBUG_CTL */