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SubjectRe: [PATCH 2/7] drm/msm/dp: reduce link rate if failed at link training 1
Quoting Kuogee Hsieh (2021-07-06 10:20:15)
> Reduce link rate and re start link training if link training 1
> failed due to loss of clock recovery done to fix Link Layer
> CTS case 4.3.1.7. Also only update voltage and pre-emphasis
> swing level after link training started to fix Link Layer CTS
> case 4.3.1.6.
>
> Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
> ---
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 86 ++++++++++++++++++++++++++--------------
> 1 file changed, 56 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 27fb0f0..6f8443d 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -83,13 +83,6 @@ struct dp_ctrl_private {
> struct completion video_comp;
> };
>
> -struct dp_cr_status {
> - u8 lane_0_1;
> - u8 lane_2_3;
> -};
> -
> -#define DP_LANE0_1_CR_DONE 0x11
> -
> static int dp_aux_link_configure(struct drm_dp_aux *aux,
> struct dp_link_info *link)
> {
> @@ -1080,7 +1073,7 @@ static int dp_ctrl_read_link_status(struct dp_ctrl_private *ctrl,
> }
>
> static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
> - struct dp_cr_status *cr, int *training_step)
> + u8 *cr, int *training_step)
> {
> int tries, old_v_level, ret = 0;
> u8 link_status[DP_LINK_STATUS_SIZE];
> @@ -1109,8 +1102,8 @@ static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
> if (ret)
> return ret;
>
> - cr->lane_0_1 = link_status[0];
> - cr->lane_2_3 = link_status[1];
> + cr[0] = link_status[0];
> + cr[1] = link_status[1];
>
> if (drm_dp_clock_recovery_ok(link_status,
> ctrl->link->link_params.num_lanes)) {
> @@ -1188,7 +1181,7 @@ static void dp_ctrl_clear_training_pattern(struct dp_ctrl_private *ctrl)
> }
>
> static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
> - struct dp_cr_status *cr, int *training_step)
> + u8 *cr, int *training_step)
> {
> int tries = 0, ret = 0;
> char pattern;
> @@ -1204,10 +1197,6 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
> else
> pattern = DP_TRAINING_PATTERN_2;
>
> - ret = dp_ctrl_update_vx_px(ctrl);
> - if (ret)
> - return ret;
> -
> ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, pattern);
> if (ret)
> return ret;
> @@ -1220,8 +1209,8 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
> ret = dp_ctrl_read_link_status(ctrl, link_status);
> if (ret)
> return ret;
> - cr->lane_0_1 = link_status[0];
> - cr->lane_2_3 = link_status[1];
> + cr[0] = link_status[0];
> + cr[1] = link_status[1];
>
> if (drm_dp_channel_eq_ok(link_status,
> ctrl->link->link_params.num_lanes)) {
> @@ -1241,7 +1230,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
> static int dp_ctrl_reinitialize_mainlink(struct dp_ctrl_private *ctrl);
>
> static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
> - struct dp_cr_status *cr, int *training_step)
> + u8 *cr, int *training_step)
> {
> int ret = 0;
> u8 encoding = DP_SET_ANSI_8B10B;
> @@ -1282,7 +1271,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
> }
>
> static int dp_ctrl_setup_main_link(struct dp_ctrl_private *ctrl,
> - struct dp_cr_status *cr, int *training_step)
> + u8 *cr, int *training_step)
> {
> int ret = 0;
>
> @@ -1496,14 +1485,14 @@ static int dp_ctrl_deinitialize_mainlink(struct dp_ctrl_private *ctrl)
> static int dp_ctrl_link_maintenance(struct dp_ctrl_private *ctrl)
> {
> int ret = 0;
> - struct dp_cr_status cr;
> + u8 cr_status[2];
> int training_step = DP_TRAINING_NONE;
>
> dp_ctrl_push_idle(&ctrl->dp_ctrl);
>
> ctrl->dp_ctrl.pixel_rate = ctrl->panel->dp_mode.drm_mode.clock;
>
> - ret = dp_ctrl_setup_main_link(ctrl, &cr, &training_step);
> + ret = dp_ctrl_setup_main_link(ctrl, cr_status, &training_step);
> if (ret)
> goto end;

Do we need to extract the link status information from deep in these
functions? Why not read it again when we need to?

>
> @@ -1634,6 +1623,41 @@ void dp_ctrl_handle_sink_request(struct dp_ctrl *dp_ctrl)
> }
> }
>
> +static bool dp_ctrl_any_lane_cr_done(struct dp_ctrl_private *ctrl,
> + u8 *cr_status)
> +
> +{
> + int i;
> + u8 status;
> + int lane = ctrl->link->link_params.num_lanes;
> +
> + for (i = 0; i < lane; i++) {
> + status = cr_status[i / 2];
> + status >>= ((i % 2) * 4);
> + if (status & DP_LANE_CR_DONE)
> + return true;
> + }
> +
> + return false;
> +}
> +
> +static bool dp_ctrl_any_lane_cr_lose(struct dp_ctrl_private *ctrl,
> + u8 *cr_status)
> +{
> + int i;
> + u8 status;
> + int lane = ctrl->link->link_params.num_lanes;
> +
> + for (i = 0; i < lane; i++) {
> + status = cr_status[i / 2];
> + status >>= ((i % 2) * 4);
> + if (!(status & DP_LANE_CR_DONE))
> + return true;
> + }
> +
> + return false;
> +}

Why not use !drm_dp_clock_recovery_ok() for dp_ctrl_any_lane_cr_lose()?
And then move dp_ctrl_any_lane_cr_done() next to
drm_dp_clock_recovery_ok() and call it drm_dp_clock_recovery_any_ok()?

> +
> int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> {
> int rc = 0;
> @@ -1641,7 +1665,7 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> u32 rate = 0;
> int link_train_max_retries = 5;
> u32 const phy_cts_pixel_clk_khz = 148500;
> - struct dp_cr_status cr;
> + u8 cr_status[2];
> unsigned int training_step;
>
> if (!dp_ctrl)
> @@ -1681,19 +1705,18 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> }
>
> training_step = DP_TRAINING_NONE;
> - rc = dp_ctrl_setup_main_link(ctrl, &cr, &training_step);
> + rc = dp_ctrl_setup_main_link(ctrl, cr_status, &training_step);
> if (rc == 0) {
> /* training completed successfully */
> break;
> } else if (training_step == DP_TRAINING_1) {
> /* link train_1 failed */
> - if (!dp_catalog_link_is_connected(ctrl->catalog)) {
> + if (!dp_catalog_link_is_connected(ctrl->catalog))
> break;
> - }
>
> rc = dp_ctrl_link_rate_down_shift(ctrl);
> if (rc < 0) { /* already in RBR = 1.6G */
> - if (cr.lane_0_1 & DP_LANE0_1_CR_DONE) {
> + if (dp_ctrl_any_lane_cr_done(ctrl, cr_status)) {
> /*
> * some lanes are ready,
> * reduce lane number
> @@ -1709,12 +1732,15 @@ int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
> }
> }
> } else if (training_step == DP_TRAINING_2) {
> - /* link train_2 failed, lower lane rate */
> - if (!dp_catalog_link_is_connected(ctrl->catalog)) {
> + /* link train_2 failed */
> + if (!dp_catalog_link_is_connected(ctrl->catalog))
> break;
> - }
>
> - rc = dp_ctrl_link_lane_down_shift(ctrl);
> + if (dp_ctrl_any_lane_cr_lose(ctrl, cr_status))
> + rc = dp_ctrl_link_rate_down_shift(ctrl);
> + else
> + rc = dp_ctrl_link_lane_down_shift(ctrl);
> +
> if (rc < 0) {
> /* end with failure */
> break; /* lane == 1 already */
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>

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