drm/hisilicon/hibmc: add dp link moduel in hibmc drivers

Add link training process functions in this moduel.

Signed-off-by: Baihan Li <[email protected]>
Signed-off-by: Yongbang Shi <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Reviewed-by: Tian Tao <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: Baihan Li

drivers/gpu/drm/hisilicon/hibmc/Makefile

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 hibmc-drm-y := hibmc_drm_drv.o hibmc_drm_de.o hibmc_drm_vdac.o hibmc_drm_i2c.o \
-	       dp/dp_aux.o
+	       dp/dp_aux.o dp/dp_link.o
 
 obj-$(CONFIG_DRM_HISI_HIBMC) += hibmc-drm.o

drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h

@@ -13,11 +13,31 @@
 #include <linux/io.h>
 #include <drm/display/drm_dp_helper.h>
 
+#define HIBMC_DP_LANE_NUM_MAX 2
+
+struct hibmc_link_status {
+	bool clock_recovered;
+	bool channel_equalized;
+};
+
+struct hibmc_link_cap {
+	u8 link_rate;
+	u8 lanes;
+};
+
+struct hibmc_dp_link {
+	struct hibmc_link_status status;
+	u8 train_set[HIBMC_DP_LANE_NUM_MAX];
+	struct hibmc_link_cap cap;
+};
+
 struct hibmc_dp_dev {
 	struct drm_dp_aux aux;
 	struct drm_device *dev;
 	void __iomem *base;
 	struct mutex lock; /* protects concurrent RW in hibmc_dp_reg_write_field() */
+	struct hibmc_dp_link link;
+	u8 dpcd[DP_RECEIVER_CAP_SIZE];
 };
 
 #define dp_field_modify(reg_value, mask, val)				\
@@ -38,5 +58,6 @@ struct hibmc_dp_dev {
 	} while (0)
 
 void hibmc_dp_aux_init(struct hibmc_dp_dev *dp);
+int hibmc_dp_link_training(struct hibmc_dp_dev *dp);
 
 #endif

drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c

@@ -0,0 +1,332 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright (c) 2024 Hisilicon Limited.
+
+#include <linux/delay.h>
+#include <drm/drm_device.h>
+#include <drm/drm_print.h>
+#include "dp_comm.h"
+#include "dp_reg.h"
+
+#define HIBMC_EQ_MAX_RETRY 5
+
+static int hibmc_dp_link_training_configure(struct hibmc_dp_dev *dp)
+{
+	u8 buf[2];
+	int ret;
+
+	/* DP 2 lane */
+	hibmc_dp_reg_write_field(dp, HIBMC_DP_PHYIF_CTRL0, HIBMC_DP_CFG_LANE_DATA_EN,
+				 dp->link.cap.lanes == 0x2 ? 0x3 : 0x1);
+	hibmc_dp_reg_write_field(dp, HIBMC_DP_DPTX_GCTL0, HIBMC_DP_CFG_PHY_LANE_NUM,
+				 dp->link.cap.lanes == 0x2 ? 0x1 : 0);
+
+	/* enhanced frame */
+	hibmc_dp_reg_write_field(dp, HIBMC_DP_VIDEO_CTRL, HIBMC_DP_CFG_STREAM_FRAME_MODE, 0x1);
+
+	/* set rate and lane count */
+	buf[0] = dp->link.cap.link_rate;
+	buf[1] = DP_LANE_COUNT_ENHANCED_FRAME_EN | dp->link.cap.lanes;
+	ret = drm_dp_dpcd_write(&dp->aux, DP_LINK_BW_SET, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		drm_dbg_dp(dp->dev, "dp aux write link rate and lanes failed, ret: %d\n", ret);
+		return ret >= 0 ? -EIO : ret;
+	}
+
+	/* set 8b/10b and downspread */
+	buf[0] = DP_SPREAD_AMP_0_5;
+	buf[1] = DP_SET_ANSI_8B10B;
+	ret = drm_dp_dpcd_write(&dp->aux, DP_DOWNSPREAD_CTRL, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		drm_dbg_dp(dp->dev, "dp aux write 8b/10b and downspread failed, ret: %d\n", ret);
+		return ret >= 0 ? -EIO : ret;
+	}
+
+	ret = drm_dp_read_dpcd_caps(&dp->aux, dp->dpcd);
+	if (ret)
+		drm_err(dp->dev, "dp aux read dpcd failed, ret: %d\n", ret);
+
+	return ret;
+}
+
+static int hibmc_dp_link_set_pattern(struct hibmc_dp_dev *dp, int pattern)
+{
+	int ret;
+	u8 val;
+	u8 buf;
+
+	buf = (u8)pattern;
+	if (pattern != DP_TRAINING_PATTERN_DISABLE && pattern != DP_TRAINING_PATTERN_4) {
+		buf |= DP_LINK_SCRAMBLING_DISABLE;
+		hibmc_dp_reg_write_field(dp, HIBMC_DP_PHYIF_CTRL0, HIBMC_DP_CFG_SCRAMBLE_EN, 0x1);
+	} else {
+		hibmc_dp_reg_write_field(dp, HIBMC_DP_PHYIF_CTRL0, HIBMC_DP_CFG_SCRAMBLE_EN, 0);
+	}
+
+	switch (pattern) {
+	case DP_TRAINING_PATTERN_DISABLE:
+		val = 0;
+		break;
+	case DP_TRAINING_PATTERN_1:
+		val = 1;
+		break;
+	case DP_TRAINING_PATTERN_2:
+		val = 2;
+		break;
+	case DP_TRAINING_PATTERN_3:
+		val = 3;
+		break;
+	case DP_TRAINING_PATTERN_4:
+		val = 4;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	hibmc_dp_reg_write_field(dp, HIBMC_DP_PHYIF_CTRL0, HIBMC_DP_CFG_PAT_SEL, val);
+
+	ret = drm_dp_dpcd_write(&dp->aux, DP_TRAINING_PATTERN_SET, &buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
+		drm_dbg_dp(dp->dev, "dp aux write training pattern set failed\n");
+		return ret >= 0 ? -EIO : ret;
+	}
+
+	return 0;
+}
+
+static int hibmc_dp_link_training_cr_pre(struct hibmc_dp_dev *dp)
+{
+	u8 *train_set = dp->link.train_set;
+	int ret;
+	u8 i;
+
+	ret = hibmc_dp_link_training_configure(dp);
+	if (ret)
+		return ret;
+
+	ret = hibmc_dp_link_set_pattern(dp, DP_TRAINING_PATTERN_1);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < dp->link.cap.lanes; i++)
+		train_set[i] = DP_TRAIN_VOLTAGE_SWING_LEVEL_2;
+
+	ret = drm_dp_dpcd_write(&dp->aux, DP_TRAINING_LANE0_SET, train_set, dp->link.cap.lanes);
+	if (ret != dp->link.cap.lanes) {
+		drm_dbg_dp(dp->dev, "dp aux write training lane set failed\n");
+		return ret >= 0 ? -EIO : ret;
+	}
+
+	return 0;
+}
+
+static bool hibmc_dp_link_get_adjust_train(struct hibmc_dp_dev *dp,
+					   u8 lane_status[DP_LINK_STATUS_SIZE])
+{
+	u8 train_set[HIBMC_DP_LANE_NUM_MAX] = {0};
+	u8 lane;
+
+	for (lane = 0; lane < dp->link.cap.lanes; lane++)
+		train_set[lane] = drm_dp_get_adjust_request_voltage(lane_status, lane) |
+				  drm_dp_get_adjust_request_pre_emphasis(lane_status, lane);
+
+	if (memcmp(dp->link.train_set, train_set, HIBMC_DP_LANE_NUM_MAX)) {
+		memcpy(dp->link.train_set, train_set, HIBMC_DP_LANE_NUM_MAX);
+		return true;
+	}
+
+	return false;
+}
+
+static inline int hibmc_dp_link_reduce_rate(struct hibmc_dp_dev *dp)
+{
+	switch (dp->link.cap.link_rate) {
+	case DP_LINK_BW_2_7:
+		dp->link.cap.link_rate = DP_LINK_BW_1_62;
+		return 0;
+	case DP_LINK_BW_5_4:
+		dp->link.cap.link_rate = DP_LINK_BW_2_7;
+		return 0;
+	case DP_LINK_BW_8_1:
+		dp->link.cap.link_rate = DP_LINK_BW_5_4;
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static inline int hibmc_dp_link_reduce_lane(struct hibmc_dp_dev *dp)
+{
+	switch (dp->link.cap.lanes) {
+	case 0x2:
+		dp->link.cap.lanes--;
+		break;
+	case 0x1:
+		drm_err(dp->dev, "dp link training reduce lane failed, already reach minimum\n");
+		return -EIO;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int hibmc_dp_link_training_cr(struct hibmc_dp_dev *dp)
+{
+	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
+	bool level_changed;
+	u32 voltage_tries;
+	u32 cr_tries;
+	int ret;
+
+	/*
+	 * DP 1.4 spec define 10 for maxtries value, for pre DP 1.4 version set a limit of 80
+	 * (4 voltage levels x 4 preemphasis levels x 5 identical voltage retries)
+	 */
+
+	voltage_tries = 1;
+	for (cr_tries = 0; cr_tries < 80; cr_tries++) {
+		drm_dp_link_train_clock_recovery_delay(&dp->aux, dp->dpcd);
+
+		ret = drm_dp_dpcd_read_link_status(&dp->aux, lane_status);
+		if (ret != DP_LINK_STATUS_SIZE) {
+			drm_err(dp->dev, "Get lane status failed\n");
+			return ret;
+		}
+
+		if (drm_dp_clock_recovery_ok(lane_status, dp->link.cap.lanes)) {
+			drm_dbg_dp(dp->dev, "dp link training cr done\n");
+			dp->link.status.clock_recovered = true;
+			return 0;
+		}
+
+		if (voltage_tries == 5) {
+			drm_dbg_dp(dp->dev, "same voltage tries 5 times\n");
+			dp->link.status.clock_recovered = false;
+			return 0;
+		}
+
+		level_changed = hibmc_dp_link_get_adjust_train(dp, lane_status);
+		ret = drm_dp_dpcd_write(&dp->aux, DP_TRAINING_LANE0_SET, dp->link.train_set,
+					dp->link.cap.lanes);
+		if (ret != dp->link.cap.lanes) {
+			drm_dbg_dp(dp->dev, "Update link training failed\n");
+			return ret >= 0 ? -EIO : ret;
+		}
+
+		voltage_tries = level_changed ? 1 : voltage_tries + 1;
+	}
+
+	drm_err(dp->dev, "dp link training clock recovery 80 times failed\n");
+	dp->link.status.clock_recovered = false;
+
+	return 0;
+}
+
+static int hibmc_dp_link_training_channel_eq(struct hibmc_dp_dev *dp)
+{
+	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
+	u8 eq_tries;
+	int ret;
+
+	ret = hibmc_dp_link_set_pattern(dp, DP_TRAINING_PATTERN_2);
+	if (ret)
+		return ret;
+
+	for (eq_tries = 0; eq_tries < HIBMC_EQ_MAX_RETRY; eq_tries++) {
+		drm_dp_link_train_channel_eq_delay(&dp->aux, dp->dpcd);
+
+		ret = drm_dp_dpcd_read_link_status(&dp->aux, lane_status);
+		if (ret != DP_LINK_STATUS_SIZE) {
+			drm_err(dp->dev, "get lane status failed\n");
+			break;
+		}
+
+		if (!drm_dp_clock_recovery_ok(lane_status, dp->link.cap.lanes)) {
+			drm_dbg_dp(dp->dev, "clock recovery check failed\n");
+			drm_dbg_dp(dp->dev, "cannot continue channel equalization\n");
+			dp->link.status.clock_recovered = false;
+			break;
+		}
+
+		if (drm_dp_channel_eq_ok(lane_status, dp->link.cap.lanes)) {
+			dp->link.status.channel_equalized = true;
+			drm_dbg_dp(dp->dev, "dp link training eq done\n");
+			break;
+		}
+
+		hibmc_dp_link_get_adjust_train(dp, lane_status);
+		ret = drm_dp_dpcd_write(&dp->aux, DP_TRAINING_LANE0_SET,
+					dp->link.train_set, dp->link.cap.lanes);
+		if (ret != dp->link.cap.lanes) {
+			drm_dbg_dp(dp->dev, "Update link training failed\n");
+			ret = (ret >= 0) ? -EIO : ret;
+			break;
+		}
+	}
+
+	if (eq_tries == HIBMC_EQ_MAX_RETRY)
+		drm_err(dp->dev, "channel equalization failed %u times\n", eq_tries);
+
+	hibmc_dp_link_set_pattern(dp, DP_TRAINING_PATTERN_DISABLE);
+
+	return ret < 0 ? ret : 0;
+}
+
+static int hibmc_dp_link_downgrade_training_cr(struct hibmc_dp_dev *dp)
+{
+	if (hibmc_dp_link_reduce_rate(dp))
+		return hibmc_dp_link_reduce_lane(dp);
+
+	return 0;
+}
+
+static int hibmc_dp_link_downgrade_training_eq(struct hibmc_dp_dev *dp)
+{
+	if ((dp->link.status.clock_recovered && !dp->link.status.channel_equalized)) {
+		if (!hibmc_dp_link_reduce_lane(dp))
+			return 0;
+	}
+
+	return hibmc_dp_link_reduce_rate(dp);
+}
+
+int hibmc_dp_link_training(struct hibmc_dp_dev *dp)
+{
+	struct hibmc_dp_link *link = &dp->link;
+	int ret;
+
+	while (true) {
+		ret = hibmc_dp_link_training_cr_pre(dp);
+		if (ret)
+			goto err;
+
+		ret = hibmc_dp_link_training_cr(dp);
+		if (ret)
+			goto err;
+
+		if (!link->status.clock_recovered) {
+			ret = hibmc_dp_link_downgrade_training_cr(dp);
+			if (ret)
+				goto err;
+			continue;
+		}
+
+		ret = hibmc_dp_link_training_channel_eq(dp);
+		if (ret)
+			goto err;
+
+		if (!link->status.channel_equalized) {
+			ret = hibmc_dp_link_downgrade_training_eq(dp);
+			if (ret)
+				goto err;
+			continue;
+		}
+
+		return 0;
+	}
+
+err:
+	hibmc_dp_link_set_pattern(dp, DP_TRAINING_PATTERN_DISABLE);
+
+	return ret;
+}