drm/msm/dp: allow voltage swing / pre emphasis of 3

Both dp_link_adjust_levels() and dp_ctrl_update_vx_px() limit swing and
pre-emphasis to 2, while the real maximum value for the sum of the
voltage swing and pre-emphasis is 3. Fix the DP code to remove this
limitation.

Fixes: c943b494 ("drm/msm/dp: add displayPort driver support")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/577006/
Link: https://lore.kernel.org/r/20240203-dp-swing-3-v1-1-6545e1706196@linaro.org

drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -1052,14 +1052,14 @@ static int dp_ctrl_update_vx_px(struct dp_ctrl_private *ctrl)
 	if (ret)
 		return ret;
 
-	if (voltage_swing_level >= DP_TRAIN_VOLTAGE_SWING_MAX) {
+	if (voltage_swing_level >= DP_TRAIN_LEVEL_MAX) {
 		drm_dbg_dp(ctrl->drm_dev,
 				"max. voltage swing level reached %d\n",
 				voltage_swing_level);
 		max_level_reached |= DP_TRAIN_MAX_SWING_REACHED;
 	}
 
-	if (pre_emphasis_level >= DP_TRAIN_PRE_EMPHASIS_MAX) {
+	if (pre_emphasis_level >= DP_TRAIN_LEVEL_MAX) {
 		drm_dbg_dp(ctrl->drm_dev,
 				"max. pre-emphasis level reached %d\n",
 				pre_emphasis_level);
@@ -1150,7 +1150,7 @@ static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
 		}
 
 		if (ctrl->link->phy_params.v_level >=
-			DP_TRAIN_VOLTAGE_SWING_MAX) {
+			DP_TRAIN_LEVEL_MAX) {
 			DRM_ERROR_RATELIMITED("max v_level reached\n");
 			return -EAGAIN;
 		}

drivers/gpu/drm/msm/dp/dp_link.c

@@ -1109,6 +1109,7 @@ int dp_link_get_colorimetry_config(struct dp_link *dp_link)
 int dp_link_adjust_levels(struct dp_link *dp_link, u8 *link_status)
 {
 	int i;
+	u8 max_p_level;
 	int v_max = 0, p_max = 0;
 	struct dp_link_private *link;
 
@@ -1140,30 +1141,29 @@ int dp_link_adjust_levels(struct dp_link *dp_link, u8 *link_status)
 	 * Adjust the voltage swing and pre-emphasis level combination to within
 	 * the allowable range.
 	 */
-	if (dp_link->phy_params.v_level > DP_TRAIN_VOLTAGE_SWING_MAX) {
+	if (dp_link->phy_params.v_level > DP_TRAIN_LEVEL_MAX) {
 		drm_dbg_dp(link->drm_dev,
 			"Requested vSwingLevel=%d, change to %d\n",
 			dp_link->phy_params.v_level,
-			DP_TRAIN_VOLTAGE_SWING_MAX);
-		dp_link->phy_params.v_level = DP_TRAIN_VOLTAGE_SWING_MAX;
+			DP_TRAIN_LEVEL_MAX);
+		dp_link->phy_params.v_level = DP_TRAIN_LEVEL_MAX;
 	}
 
-	if (dp_link->phy_params.p_level > DP_TRAIN_PRE_EMPHASIS_MAX) {
+	if (dp_link->phy_params.p_level > DP_TRAIN_LEVEL_MAX) {
 		drm_dbg_dp(link->drm_dev,
 			"Requested preEmphasisLevel=%d, change to %d\n",
 			dp_link->phy_params.p_level,
-			DP_TRAIN_PRE_EMPHASIS_MAX);
-		dp_link->phy_params.p_level = DP_TRAIN_PRE_EMPHASIS_MAX;
+			DP_TRAIN_LEVEL_MAX);
+		dp_link->phy_params.p_level = DP_TRAIN_LEVEL_MAX;
 	}
 
-	if ((dp_link->phy_params.p_level > DP_TRAIN_PRE_EMPHASIS_LVL_1)
-		&& (dp_link->phy_params.v_level ==
-			DP_TRAIN_VOLTAGE_SWING_LVL_2)) {
+	max_p_level = DP_TRAIN_LEVEL_MAX - dp_link->phy_params.v_level;
+	if (dp_link->phy_params.p_level > max_p_level) {
 		drm_dbg_dp(link->drm_dev,
 			"Requested preEmphasisLevel=%d, change to %d\n",
 			dp_link->phy_params.p_level,
-			DP_TRAIN_PRE_EMPHASIS_LVL_1);
-		dp_link->phy_params.p_level = DP_TRAIN_PRE_EMPHASIS_LVL_1;
+			max_p_level);
+		dp_link->phy_params.p_level = max_p_level;
 	}
 
 	drm_dbg_dp(link->drm_dev, "adjusted: v_level=%d, p_level=%d\n",

drivers/gpu/drm/msm/dp/dp_link.h

@@ -19,19 +19,7 @@ struct dp_link_info {
 	unsigned long capabilities;
 };
 
-enum dp_link_voltage_level {
-	DP_TRAIN_VOLTAGE_SWING_LVL_0	= 0,
-	DP_TRAIN_VOLTAGE_SWING_LVL_1	= 1,
-	DP_TRAIN_VOLTAGE_SWING_LVL_2	= 2,
-	DP_TRAIN_VOLTAGE_SWING_MAX	= DP_TRAIN_VOLTAGE_SWING_LVL_2,
-};
-
-enum dp_link_preemaphasis_level {
-	DP_TRAIN_PRE_EMPHASIS_LVL_0	= 0,
-	DP_TRAIN_PRE_EMPHASIS_LVL_1	= 1,
-	DP_TRAIN_PRE_EMPHASIS_LVL_2	= 2,
-	DP_TRAIN_PRE_EMPHASIS_MAX	= DP_TRAIN_PRE_EMPHASIS_LVL_2,
-};
+#define DP_TRAIN_LEVEL_MAX	3
 
 struct dp_link_test_video {
 	u32 test_video_pattern;