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

[Kuogee Hsieh]

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.baryshkov at linaro.org>
> Reviewed-by: Kuogee Hsieh <quic_khsieh at quicinc.com>
Tested-by: Kuogee Hsieh <quic_khsieh at 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,