Re: [PATCH 2/7] drm/msm/dp: reduce link rate if failed at link training 1

From: khsieh
Date: Fri Jul 09 2021 - 13:46:48 EST

On 2021-07-08 00:33, Stephen Boyd wrote:
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@xxxxxxxxxxxxxx>
---
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()?
ok,

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()?
no understand how it work, can you elaborate it more?

+
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 */
--
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