Re: [PATCH] drm/msm/dp: allow voltage swing / pre emphasis of 3

Mon, 01 Apr 2024 13:15:08 -0700 


On 4/1/2024 9:25 AM, Kuogee Hsieh wrote:


On 2/3/2024 5:47 AM, Dmitry Baryshkov wrote:

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: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
Signed-off-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>

Reviewed-by: Kuogee Hsieh <quic_khs...@quicinc.com>

Tested-by: Kuogee Hsieh <quic_khs...@quicinc.com>

---
  drivers/gpu/drm/msm/dp/dp_ctrl.c |  6 +++---
  drivers/gpu/drm/msm/dp/dp_link.c | 22 +++++++++++-----------
  drivers/gpu/drm/msm/dp/dp_link.h | 14 +-------------
  3 files changed, 15 insertions(+), 27 deletions(-)


diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c 
b/drivers/gpu/drm/msm/dp/dp_ctrl.c

index 77a8d9366ed7..26241970019f 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c

@@ -1024,14 +1024,14 @@ 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);

@@ -1122,7 +1122,7 @@ 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;
          }

diff --git a/drivers/gpu/drm/msm/dp/dp_link.c 
b/drivers/gpu/drm/msm/dp/dp_link.c

index 98427d45e9a7..e7da0571ecff 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.c
+++ b/drivers/gpu/drm/msm/dp/dp_link.c

@@ -1107,6 +1107,7 @@ 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;

  @@ -1138,30 +1139,29 @@ 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",

diff --git a/drivers/gpu/drm/msm/dp/dp_link.h 
b/drivers/gpu/drm/msm/dp/dp_link.h

index 9dd4dd926530..79c3a02b8dac 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.h
+++ b/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;

---
base-commit: 41d66f96d0f15a0a2ad6fa2208f6bac1a66cbd52
change-id: 20240203-dp-swing-3-b64ffce415d9

Best regards,






















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