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Message-ID: <Z8/yQsiaPtJHKBUl@linaro.org>
Date: Tue, 11 Mar 2025 10:20:18 +0200
From: Abel Vesa <abel.vesa@...aro.org>
To: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
Rob Clark <robdclark@...il.com>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
Sean Paul <sean@...rly.run>,
Marijn Suijten <marijn.suijten@...ainline.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
laurentiu.tudor1@...l.com, johan@...nel.org
Subject: Re: [PATCH v1 2/2] drm/msm/dp: Introduce link training per-segment
for LTTPRs
On 25-03-10 22:05:52, Aleksandrs Vinarskis wrote:
> DisplayPort requires per-segment link training when LTTPR are switched
> to non-transparent mode, starting with LTTPR closest to the source.
> Only when each segment is trained individually, source can link train
> to sink.
>
> Implement per-segment link traning when LTTPR(s) are detected, to
> support external docking stations. On higher level, changes are:
>
> * Pass phy being trained down to all required helpers
> * Run CR, EQ link training per phy
> * Set voltage swing, pre-emphasis levels per phy
>
> This ensures successful link training both when connected directly to
> the monitor (single LTTPR onboard most X1E laptops) and via the docking
> station (at least two LTTPRs). This does not address/resolve underlying
> mainlink initialization issues.
>
> Signed-off-by: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
Reviewed-by: Abel Vesa <abel.vesa@...aro.org>
> ---
> drivers/gpu/drm/msm/dp/dp_ctrl.c | 136 +++++++++++++++++++---------
> drivers/gpu/drm/msm/dp/dp_ctrl.h | 2 +-
> drivers/gpu/drm/msm/dp/dp_display.c | 4 +-
> 3 files changed, 98 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index d8633a596f8d..20f07ef46ef3 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -79,6 +79,8 @@ struct msm_dp_ctrl_private {
> struct msm_dp_link *link;
> struct msm_dp_catalog *catalog;
>
> + int *lttpr_count;
> +
> struct phy *phy;
>
> unsigned int num_core_clks;
> @@ -1034,7 +1036,8 @@ static int msm_dp_ctrl_set_vx_px(struct msm_dp_ctrl_private *ctrl,
> return 0;
> }
>
> -static int msm_dp_ctrl_update_vx_px(struct msm_dp_ctrl_private *ctrl)
> +static int msm_dp_ctrl_update_phy_vx_px(struct msm_dp_ctrl_private *ctrl,
> + enum drm_dp_phy dp_phy)
> {
> struct msm_dp_link *link = ctrl->link;
> int ret = 0, lane, lane_cnt;
> @@ -1075,8 +1078,12 @@ static int msm_dp_ctrl_update_vx_px(struct msm_dp_ctrl_private *ctrl)
>
> drm_dbg_dp(ctrl->drm_dev, "sink: p|v=0x%x\n",
> voltage_swing_level | pre_emphasis_level);
> - ret = drm_dp_dpcd_write(ctrl->aux, DP_TRAINING_LANE0_SET,
> - buf, lane_cnt);
> +
> + int reg = dp_phy == DP_PHY_DPRX ?
> + DP_TRAINING_LANE0_SET :
> + DP_TRAINING_LANE0_SET_PHY_REPEATER(dp_phy);
> +
> + ret = drm_dp_dpcd_write(ctrl->aux, reg, buf, lane_cnt);
> if (ret == lane_cnt)
> ret = 0;
>
> @@ -1084,10 +1091,13 @@ static int msm_dp_ctrl_update_vx_px(struct msm_dp_ctrl_private *ctrl)
> }
>
> static bool msm_dp_ctrl_train_pattern_set(struct msm_dp_ctrl_private *ctrl,
> - u8 pattern)
> + u8 pattern, enum drm_dp_phy dp_phy)
> {
> u8 buf;
> int ret = 0;
> + int reg = dp_phy == DP_PHY_DPRX ?
> + DP_TRAINING_PATTERN_SET :
> + DP_TRAINING_PATTERN_SET_PHY_REPEATER(dp_phy);
>
> drm_dbg_dp(ctrl->drm_dev, "sink: pattern=%x\n", pattern);
>
> @@ -1096,7 +1106,7 @@ static bool msm_dp_ctrl_train_pattern_set(struct msm_dp_ctrl_private *ctrl,
> if (pattern && pattern != DP_TRAINING_PATTERN_4)
> buf |= DP_LINK_SCRAMBLING_DISABLE;
>
> - ret = drm_dp_dpcd_writeb(ctrl->aux, DP_TRAINING_PATTERN_SET, buf);
> + ret = drm_dp_dpcd_writeb(ctrl->aux, reg, buf);
> return ret == 1;
> }
>
> @@ -1115,12 +1125,16 @@ static int msm_dp_ctrl_read_link_status(struct msm_dp_ctrl_private *ctrl,
> }
>
> static int msm_dp_ctrl_link_train_1(struct msm_dp_ctrl_private *ctrl,
> - int *training_step)
> + int *training_step, enum drm_dp_phy dp_phy)
> {
> + int delay_us;
> int tries, old_v_level, ret = 0;
> u8 link_status[DP_LINK_STATUS_SIZE];
> int const maximum_retries = 4;
>
> + delay_us = drm_dp_read_clock_recovery_delay(ctrl->aux,
> + ctrl->panel->dpcd, dp_phy, false);
> +
> msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
>
> *training_step = DP_TRAINING_1;
> @@ -1129,18 +1143,19 @@ static int msm_dp_ctrl_link_train_1(struct msm_dp_ctrl_private *ctrl,
> if (ret)
> return ret;
> msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_1 |
> - DP_LINK_SCRAMBLING_DISABLE);
> + DP_LINK_SCRAMBLING_DISABLE, dp_phy);
>
> - ret = msm_dp_ctrl_update_vx_px(ctrl);
> + msm_dp_link_reset_phy_params_vx_px(ctrl->link);
> + ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
> if (ret)
> return ret;
>
> tries = 0;
> old_v_level = ctrl->link->phy_params.v_level;
> for (tries = 0; tries < maximum_retries; tries++) {
> - drm_dp_link_train_clock_recovery_delay(ctrl->aux, ctrl->panel->dpcd);
> + fsleep(delay_us);
>
> - ret = msm_dp_ctrl_read_link_status(ctrl, link_status);
> + ret = drm_dp_dpcd_read_phy_link_status(ctrl->aux, dp_phy, link_status);
> if (ret)
> return ret;
>
> @@ -1161,7 +1176,7 @@ static int msm_dp_ctrl_link_train_1(struct msm_dp_ctrl_private *ctrl,
> }
>
> msm_dp_link_adjust_levels(ctrl->link, link_status);
> - ret = msm_dp_ctrl_update_vx_px(ctrl);
> + ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
> if (ret)
> return ret;
> }
> @@ -1213,21 +1228,31 @@ static int msm_dp_ctrl_link_lane_down_shift(struct msm_dp_ctrl_private *ctrl)
> return 0;
> }
>
> -static void msm_dp_ctrl_clear_training_pattern(struct msm_dp_ctrl_private *ctrl)
> +static void msm_dp_ctrl_clear_training_pattern(struct msm_dp_ctrl_private *ctrl,
> + enum drm_dp_phy dp_phy)
> {
> - msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_DISABLE);
> - drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);
> + int delay_us;
> +
> + msm_dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_DISABLE, dp_phy);
> +
> + delay_us = drm_dp_read_channel_eq_delay(ctrl->aux,
> + ctrl->panel->dpcd, dp_phy, false);
> + fsleep(delay_us);
> }
>
> static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl,
> - int *training_step)
> + int *training_step, enum drm_dp_phy dp_phy)
> {
> + int delay_us;
> int tries = 0, ret = 0;
> u8 pattern;
> u32 state_ctrl_bit;
> int const maximum_retries = 5;
> u8 link_status[DP_LINK_STATUS_SIZE];
>
> + delay_us = drm_dp_read_channel_eq_delay(ctrl->aux,
> + ctrl->panel->dpcd, dp_phy, false);
> +
> msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
>
> *training_step = DP_TRAINING_2;
> @@ -1247,12 +1272,12 @@ static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl,
> if (ret)
> return ret;
>
> - msm_dp_ctrl_train_pattern_set(ctrl, pattern);
> + msm_dp_ctrl_train_pattern_set(ctrl, pattern, dp_phy);
>
> for (tries = 0; tries <= maximum_retries; tries++) {
> - drm_dp_link_train_channel_eq_delay(ctrl->aux, ctrl->panel->dpcd);
> + fsleep(delay_us);
>
> - ret = msm_dp_ctrl_read_link_status(ctrl, link_status);
> + ret = drm_dp_dpcd_read_phy_link_status(ctrl->aux, dp_phy, link_status);
> if (ret)
> return ret;
>
> @@ -1262,7 +1287,7 @@ static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl,
> }
>
> msm_dp_link_adjust_levels(ctrl->link, link_status);
> - ret = msm_dp_ctrl_update_vx_px(ctrl);
> + ret = msm_dp_ctrl_update_phy_vx_px(ctrl, dp_phy);
> if (ret)
> return ret;
>
> @@ -1271,10 +1296,32 @@ static int msm_dp_ctrl_link_train_2(struct msm_dp_ctrl_private *ctrl,
> return -ETIMEDOUT;
> }
>
> +static int msm_dp_ctrl_link_train_1_2(struct msm_dp_ctrl_private *ctrl,
> + int *training_step, enum drm_dp_phy dp_phy)
> +{
> + int ret;
> +
> + ret = msm_dp_ctrl_link_train_1(ctrl, training_step, dp_phy);
> + if (ret) {
> + DRM_ERROR("link training #1 on phy %d failed. ret=%d\n", dp_phy, ret);
> + return ret;
> + }
> + drm_dbg_dp(ctrl->drm_dev, "link training #1 on phy %d successful\n", dp_phy);
> +
> + ret = msm_dp_ctrl_link_train_2(ctrl, training_step, dp_phy);
> + if (ret) {
> + DRM_ERROR("link training #2 on phy %d failed. ret=%d\n", dp_phy, ret);
> + return ret;
> + }
> + drm_dbg_dp(ctrl->drm_dev, "link training #2 on phy %d successful\n", dp_phy);
> +
> + return 0;
> +}
> +
> static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl,
> int *training_step)
> {
> - int ret = 0;
> + int ret = 0, i;
> const u8 *dpcd = ctrl->panel->dpcd;
> u8 encoding[] = { 0, DP_SET_ANSI_8B10B };
> u8 assr;
> @@ -1286,8 +1333,6 @@ static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl,
> link_info.rate = ctrl->link->link_params.rate;
> link_info.capabilities = DP_LINK_CAP_ENHANCED_FRAMING;
>
> - msm_dp_link_reset_phy_params_vx_px(ctrl->link);
> -
> msm_dp_aux_link_configure(ctrl->aux, &link_info);
>
> if (drm_dp_max_downspread(dpcd))
> @@ -1302,23 +1347,29 @@ static int msm_dp_ctrl_link_train(struct msm_dp_ctrl_private *ctrl,
> &assr, 1);
> }
>
> - ret = msm_dp_ctrl_link_train_1(ctrl, training_step);
> + for (i = *ctrl->lttpr_count - 1; i >= 0; i--) {
> + enum drm_dp_phy dp_phy = DP_PHY_LTTPR(i);
> +
> + ret = msm_dp_ctrl_link_train_1_2(ctrl, training_step, dp_phy);
> + msm_dp_ctrl_clear_training_pattern(ctrl, dp_phy);
> +
> + if (ret)
> + break;
> + }
> +
> if (ret) {
> - DRM_ERROR("link training #1 failed. ret=%d\n", ret);
> + DRM_ERROR("link training of LTTPR(s) failed. ret=%d\n", ret);
> goto end;
> }
>
> - /* print success info as this is a result of user initiated action */
> - drm_dbg_dp(ctrl->drm_dev, "link training #1 successful\n");
> -
> - ret = msm_dp_ctrl_link_train_2(ctrl, training_step);
> + ret = msm_dp_ctrl_link_train_1_2(ctrl, training_step, DP_PHY_DPRX);
> if (ret) {
> - DRM_ERROR("link training #2 failed. ret=%d\n", ret);
> + DRM_ERROR("link training on sink failed. ret=%d\n", ret);
> goto end;
> }
>
> /* print success info as this is a result of user initiated action */
> - drm_dbg_dp(ctrl->drm_dev, "link training #2 successful\n");
> + drm_dbg_dp(ctrl->drm_dev, "link training on sink successful\n");
>
> end:
> msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
> @@ -1636,7 +1687,7 @@ static int msm_dp_ctrl_link_maintenance(struct msm_dp_ctrl_private *ctrl)
> if (ret)
> goto end;
>
> - msm_dp_ctrl_clear_training_pattern(ctrl);
> + msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
>
> msm_dp_catalog_ctrl_state_ctrl(ctrl->catalog, DP_STATE_CTRL_SEND_VIDEO);
>
> @@ -1660,7 +1711,7 @@ static bool msm_dp_ctrl_send_phy_test_pattern(struct msm_dp_ctrl_private *ctrl)
> return false;
> }
> msm_dp_catalog_ctrl_send_phy_pattern(ctrl->catalog, pattern_requested);
> - msm_dp_ctrl_update_vx_px(ctrl);
> + msm_dp_ctrl_update_phy_vx_px(ctrl, DP_PHY_DPRX);
> msm_dp_link_send_test_response(ctrl->link);
>
> pattern_sent = msm_dp_catalog_ctrl_read_phy_pattern(ctrl->catalog);
> @@ -1902,7 +1953,7 @@ int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl)
> }
>
> /* stop link training before start re training */
> - msm_dp_ctrl_clear_training_pattern(ctrl);
> + msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
> }
>
> rc = msm_dp_ctrl_reinitialize_mainlink(ctrl);
> @@ -1926,7 +1977,7 @@ int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl)
> * link training failed
> * end txing train pattern here
> */
> - msm_dp_ctrl_clear_training_pattern(ctrl);
> + msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
>
> msm_dp_ctrl_deinitialize_mainlink(ctrl);
> rc = -ECONNRESET;
> @@ -1997,7 +2048,7 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, bool force_link_train
> msm_dp_ctrl_link_retrain(ctrl);
>
> /* stop txing train pattern to end link training */
> - msm_dp_ctrl_clear_training_pattern(ctrl);
> + msm_dp_ctrl_clear_training_pattern(ctrl, DP_PHY_DPRX);
>
> /*
> * Set up transfer unit values and set controller state to send
> @@ -2207,7 +2258,7 @@ static int msm_dp_ctrl_clk_init(struct msm_dp_ctrl *msm_dp_ctrl)
>
> struct msm_dp_ctrl *msm_dp_ctrl_get(struct device *dev, struct msm_dp_link *link,
> struct msm_dp_panel *panel, struct drm_dp_aux *aux,
> - struct msm_dp_catalog *catalog,
> + struct msm_dp_catalog *catalog, int *lttpr_count,
> struct phy *phy)
> {
> struct msm_dp_ctrl_private *ctrl;
> @@ -2242,12 +2293,13 @@ struct msm_dp_ctrl *msm_dp_ctrl_get(struct device *dev, struct msm_dp_link *link
> init_completion(&ctrl->video_comp);
>
> /* in parameters */
> - ctrl->panel = panel;
> - ctrl->aux = aux;
> - ctrl->link = link;
> - ctrl->catalog = catalog;
> - ctrl->dev = dev;
> - ctrl->phy = phy;
> + ctrl->panel = panel;
> + ctrl->aux = aux;
> + ctrl->link = link;
> + ctrl->catalog = catalog;
> + ctrl->dev = dev;
> + ctrl->phy = phy;
> + ctrl->lttpr_count = lttpr_count;
>
> ret = msm_dp_ctrl_clk_init(&ctrl->msm_dp_ctrl);
> if (ret) {
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> index b7abfedbf574..3fb45b138b31 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.h
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h
> @@ -27,7 +27,7 @@ irqreturn_t msm_dp_ctrl_isr(struct msm_dp_ctrl *msm_dp_ctrl);
> void msm_dp_ctrl_handle_sink_request(struct msm_dp_ctrl *msm_dp_ctrl);
> struct msm_dp_ctrl *msm_dp_ctrl_get(struct device *dev, struct msm_dp_link *link,
> struct msm_dp_panel *panel, struct drm_dp_aux *aux,
> - struct msm_dp_catalog *catalog,
> + struct msm_dp_catalog *catalog, int *lttpr_count,
> struct phy *phy);
>
> void msm_dp_ctrl_reset_irq_ctrl(struct msm_dp_ctrl *msm_dp_ctrl, bool enable);
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 2edbc6adfde5..5fcc5951797b 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -108,6 +108,7 @@ struct msm_dp_display_private {
> struct msm_dp_event event_list[DP_EVENT_Q_MAX];
> spinlock_t event_lock;
>
> + int lttpr_count;
> u8 lttpr_common_caps[DP_LTTPR_COMMON_CAP_SIZE];
>
> bool wide_bus_supported;
> @@ -397,7 +398,7 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
> if (rc)
> goto end;
>
> - msm_dp_display_lttpr_init(dp, dpcd);
> + dp->lttpr_count = msm_dp_display_lttpr_init(dp, dpcd);
>
> rc = msm_dp_panel_read_sink_caps(dp->panel, dp->lttpr_common_caps, connector);
> if (rc)
> @@ -798,6 +799,7 @@ static int msm_dp_init_sub_modules(struct msm_dp_display_private *dp)
>
> dp->ctrl = msm_dp_ctrl_get(dev, dp->link, dp->panel, dp->aux,
> dp->catalog,
> + &dp->lttpr_count,
> phy);
> if (IS_ERR(dp->ctrl)) {
> rc = PTR_ERR(dp->ctrl);
> --
> 2.45.2
>
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