[PATCH 5.14 290/432] drm/msm/dp: reduce link rate if failed at link training 1

Greg Kroah-Hartman
2021-09-16T17:40:59Z

From: Kuogee Hsieh <khsieh@codeaurora.org>

[ Upstream commit 4b85d405cfe938ae7ad61656484ae88dee289e3b ]

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.

Changes in V2:
-- replaced cr_status with link_status[DP_LINK_STATUS_SIZE]
-- replaced dp_ctrl_any_lane_cr_done() with dp_ctrl_colco_recovery_any_ok()
-- replaced dp_ctrl_any_ane_cr_lose() with !drm_dp_clock_recovery_ok()

Changes in V3:
-- return failed if lane_count <= 1

Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1628196295-7382-3-git-send-email-khsieh@codeaurora.org
[remove unused cr_status variable]
Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/msm/dp/dp_ctrl.c | 78 ++++++++++++++++++--------------
1 file changed, 44 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index eaddfd739885..30d20e3beb29 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -81,13 +81,6 @@ 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)
{
@@ -1078,7 +1071,7 @@ 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)
+ int *training_step)
{
int tries, old_v_level, ret = 0;
u8 link_status[DP_LINK_STATUS_SIZE];
@@ -1107,9 +1100,6 @@ 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];
-
if (drm_dp_clock_recovery_ok(link_status,
ctrl->link->link_params.num_lanes)) {
return 0;
@@ -1186,7 +1176,7 @@ 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)
+ int *training_step)
{
int tries = 0, ret = 0;
char pattern;
@@ -1202,10 +1192,6 @@ 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;
@@ -1218,8 +1204,6 @@ 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];

if (drm_dp_channel_eq_ok(link_status,
ctrl->link->link_params.num_lanes)) {
@@ -1239,7 +1223,7 @@ 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)
+ int *training_step)
{
int ret = 0;
u8 encoding = DP_SET_ANSI_8B10B;
@@ -1255,7 +1239,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
drm_dp_dpcd_write(ctrl->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
&encoding, 1);

- ret = dp_ctrl_link_train_1(ctrl, cr, training_step);
+ ret = dp_ctrl_link_train_1(ctrl, training_step);
if (ret) {
DRM_ERROR("link training #1 failed. ret=%d\n", ret);
goto end;
@@ -1264,7 +1248,7 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
/* print success info as this is a result of user initiated action */
DRM_DEBUG_DP("link training #1 successful\n");

- ret = dp_ctrl_link_train_2(ctrl, cr, training_step);
+ ret = dp_ctrl_link_train_2(ctrl, training_step);
if (ret) {
DRM_ERROR("link training #2 failed. ret=%d\n", ret);
goto end;
@@ -1280,7 +1264,7 @@ 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)
+ int *training_step)
{
int ret = 0;

@@ -1295,7 +1279,7 @@ static int dp_ctrl_setup_main_link(struct dp_ctrl_private *ctrl,
* a link training pattern, we have to first do soft reset.
*/

- ret = dp_ctrl_link_train(ctrl, cr, training_step);
+ ret = dp_ctrl_link_train(ctrl, training_step);

return ret;
}
@@ -1492,14 +1476,13 @@ 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;
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, &training_step);
if (ret)
goto end;

@@ -1630,6 +1613,25 @@ void dp_ctrl_handle_sink_request(struct dp_ctrl *dp_ctrl)
}
}

+static bool dp_ctrl_clock_recovery_any_ok(
+ const u8 link_status[DP_LINK_STATUS_SIZE],
+ int lane_count)
+{
+ int reduced_cnt;
+
+ if (lane_count <= 1)
+ return false;
+
+ /*
+ * only interested in the lane number after reduced
+ * lane_count = 4, then only interested in 2 lanes
+ * lane_count = 2, then only interested in 1 lane
+ */
+ reduced_cnt = lane_count >> 1;
+
+ return drm_dp_clock_recovery_ok(link_status, reduced_cnt);
+}
+
int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
{
int rc = 0;
@@ -1637,7 +1639,7 @@ 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 link_status[DP_LINK_STATUS_SIZE];
unsigned int training_step;

if (!dp_ctrl)
@@ -1677,19 +1679,21 @@ 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, &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;
- }
+
+ dp_ctrl_read_link_status(ctrl, link_status);

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_clock_recovery_any_ok(link_status,
+ ctrl->link->link_params.num_lanes)) {
/*
* some lanes are ready,
* reduce lane number
@@ -1705,12 +1709,18 @@ 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);
+ dp_ctrl_read_link_status(ctrl, link_status);
+
+ if (!drm_dp_clock_recovery_ok(link_status,
+ ctrl->link->link_params.num_lanes))
+ 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 */
--
2.30.2