From: baihan li <libaihan@huawei.com>

Add link training process functions in this moduel.

Signed-off-by: baihan li <libaihan@huawei.com>
Signed-off-by: yongbang shi <shiyongbang@huawei.com>
---
Changelog:
v2 -> v3:
  - using switchcase in dp_link_reduce_lane, suggested by Dmitry Baryshkov.
  - deleting dp_link_pattern2dpcd function and using macros directly, suggested by Dmitry Baryshkov.
  - deleting EFAULT error codes, suggested by Dmitry Baryshkov.
v1 -> v2:
  - using drm_dp_* functions implement dp link training process, suggested by Jani Nikula.
  - fix build errors reported by kernel test robot <lkp@intel.com>
    Closes: https://lore.kernel.org/oe-kbuild-all/202410031735.8iRZZR6T-lkp@intel.com/
  v1:https://lore.kernel.org/all/20240930100610.782363-1-shiyongbang@huawei.com/
---
 drivers/gpu/drm/hisilicon/hibmc/Makefile     |   2 +-
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c | 346 +++++++++++++++++++
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h |  25 ++
 drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h  |   8 +
 4 files changed, 380 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
 create mode 100644 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h

diff --git a/drivers/gpu/drm/hisilicon/hibmc/Makefile b/drivers/gpu/drm/hisilicon/hibmc/Makefile
index 8770ec6dfffd..94d77da88bbf 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/Makefile
+++ b/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
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
new file mode 100644
index 000000000000..7146de020c93
--- /dev/null
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
@@ -0,0 +1,346 @@
+// 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"
+#include "dp_link.h"
+#include "dp_aux.h"
+
+const u8 link_rate_map[] = {DP_LINK_BW_1_62, DP_LINK_BW_2_7,
+			    DP_LINK_BW_5_4, DP_LINK_BW_8_1};
+
+static int hibmc_dp_link_training_configure(struct dp_dev *dp)
+{
+	u8 buf[2];
+	int ret;
+
+	/* DP 2 lane */
+	dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_LANE_DATA_EN,
+			   dp->link.cap.lanes == DP_LANE_NUM_2 ? 0x3 : 0x1);
+	dp_reg_write_field(dp->base + DP_DPTX_GCTL0, DP_CFG_PHY_LANE_NUM,
+			   dp->link.cap.lanes == DP_LANE_NUM_2 ? 0x1 : 0);
+
+	/* enhanced frame */
+	dp_reg_write_field(dp->base + DP_VIDEO_CTRL, DP_CFG_STREAM_FRAME_MODE, 0x1);
+
+	/* set rate and lane count */
+	buf[0] = hibmc_dp_get_link_rate(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] = 0x10;
+	buf[1] = 0x1;
+	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 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;
+		dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_SCRAMBLE_EN, 0x1);
+	} else {
+		dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_SCRAMBLE_EN, 0);
+	}
+
+	switch (pattern) {
+	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:
+		val = 0;
+	}
+
+	dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, 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 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 dp_dev *dp, u8 lane_status[DP_LINK_STATUS_SIZE])
+{
+	u8 pre_emph[DP_LANE_NUM_MAX] = {0};
+	u8 voltage[DP_LANE_NUM_MAX] = {0};
+	bool changed = false;
+	u8 train_set;
+	u8 lane;
+
+	for (lane = 0; lane < dp->link.cap.lanes; lane++) {
+		voltage[lane] = drm_dp_get_adjust_request_voltage(lane_status, lane);
+		pre_emph[lane] = drm_dp_get_adjust_request_pre_emphasis(lane_status, lane);
+	}
+
+	for (lane = 0; lane < dp->link.cap.lanes; lane++) {
+		train_set = voltage[lane] | pre_emph[lane];
+		if (dp->link.train_set[lane] != train_set) {
+			changed = true;
+			dp->link.train_set[lane] = train_set;
+		}
+	}
+
+	return changed;
+}
+
+u8 hibmc_dp_get_link_rate(u8 index)
+{
+	return link_rate_map[index];
+}
+
+static int hibmc_dp_link_reduce_rate(struct dp_dev *dp)
+{
+	if (dp->link.cap.link_rate > 0) {
+		dp->link.cap.link_rate--;
+		return 0;
+	}
+
+	drm_err(dp->dev, "dp link training reduce rate failed, already lowest rate\n");
+
+	return -ELNRNG;
+}
+
+static int hibmc_dp_link_reduce_lane(struct dp_dev *dp)
+{
+	switch (dp->link.cap.lanes) {
+	case DP_LANE_NUM_2:
+		dp->link.cap.lanes--;
+		break;
+	case DP_LANE_NUM_1:
+		drm_err(dp->dev, "dp link training reduce lane failed, already reach minimum\n");
+		return -ELNRNG;
+	}
+
+	return 0;
+}
+
+static int hibmc_dp_link_training_cr(struct dp_dev *dp)
+{
+	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
+	bool level_changed;
+	u32 voltage_tries;
+	u32 cr_tries;
+	u32 max_cr;
+	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)
+	 */
+	max_cr = dp->link.cap.rx_dpcd_revision >= DP_DPCD_REV_14 ? 10 : 80;
+
+	voltage_tries = 1;
+	for (cr_tries = 0; cr_tries < max_cr; 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_info(dp->dev, "dp link training cr done\n");
+			dp->link.status.clock_recovered = true;
+			return 0;
+		}
+
+		if (voltage_tries == 5) {
+			drm_info(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 %u timers failed\n", max_cr);
+	dp->link.status.clock_recovered = false;
+
+	return 0;
+}
+
+static int hibmc_dp_link_training_channel_eq(struct dp_dev *dp)
+{
+	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
+	u8 eq_tries;
+	int tps;
+	int ret;
+
+	if (dp->link.cap.is_tps4)
+		tps = DP_TRAINING_PATTERN_4;
+	else if (dp->link.cap.is_tps3)
+		tps = DP_TRAINING_PATTERN_3;
+	else
+		tps = DP_TRAINING_PATTERN_2;
+
+	ret = hibmc_dp_link_set_pattern(dp, tps);
+	if (ret)
+		return ret;
+
+	for (eq_tries = 0; eq_tries < 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_info(dp->dev, "clock recovery check failed\n");
+			drm_info(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_info(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 == 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 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 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 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;
+}
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h
new file mode 100644
index 000000000000..b4958d122083
--- /dev/null
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (c) 2024 Hisilicon Limited. */
+
+#ifndef DP_LINK_H
+#define DP_LINK_H
+
+#include "dp_comm.h"
+
+#define DP_LANE_NUM_MAX		2
+#define DP_LANE_STATUS_SIZE	1
+#define DP_LANE_NUM_1		0x1
+#define DP_LANE_NUM_2		0x2
+
+enum dp_pattern_e {
+	DP_PATTERN_NO = 0,
+	DP_PATTERN_TPS1,
+	DP_PATTERN_TPS2,
+	DP_PATTERN_TPS3,
+	DP_PATTERN_TPS4,
+};
+
+int hibmc_dp_link_training(struct dp_dev *dp);
+u8 hibmc_dp_get_link_rate(u8 index);
+
+#endif
diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
index 83cf0cc06ae2..1032f6cde761 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
+++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
@@ -12,16 +12,24 @@
 #define DP_AUX_RD_DATA0			0x64
 #define DP_AUX_REQ			0x74
 #define DP_AUX_STATUS			0x78
+#define DP_PHYIF_CTRL0			0xa0
+#define DP_VIDEO_CTRL			0x100
 #define DP_DPTX_RST_CTRL		0x700
+#define DP_DPTX_GCTL0			0x708
 
 #define DP_CFG_AUX_SYNC_LEN_SEL			BIT(1)
 #define DP_CFG_AUX_TIMER_TIMEOUT		BIT(2)
+#define DP_CFG_STREAM_FRAME_MODE		BIT(6)
 #define DP_CFG_AUX_MIN_PULSE_NUM		GENMASK(13, 9)
+#define DP_CFG_LANE_DATA_EN			GENMASK(11, 8)
+#define DP_CFG_PHY_LANE_NUM			GENMASK(2, 1)
 #define DP_CFG_AUX_REQ				BIT(0)
 #define DP_CFG_AUX_RST_N			BIT(4)
 #define DP_CFG_AUX_TIMEOUT			BIT(0)
 #define DP_CFG_AUX_READY_DATA_BYTE		GENMASK(16, 12)
 #define DP_CFG_AUX				GENMASK(24, 17)
 #define DP_CFG_AUX_STATUS			GENMASK(11, 4)
+#define DP_CFG_SCRAMBLE_EN			BIT(0)
+#define DP_CFG_PAT_SEL				GENMASK(7, 4)
 
 #endif
-- 
2.33.0

Hi Yongbang,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v6.12-rc6 next-20241101]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yongbang-Shi/drm-hisilicon-hibmc-add-dp-aux-in-hibmc/20241101-185648
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20241101105028.2177274-3-shiyongbang%40huawei.com
patch subject: [PATCH V3 drm-dp 2/4] drm/hisilicon/hibmc: add dp link moduel in hibmc
config: csky-randconfig-r121-20241103 (https://download.01.org/0day-ci/archive/20241104/202411041559.WIfxRN6n-lkp@intel.com/config)
compiler: csky-linux-gcc (GCC) 14.1.0
reproduce: (https://download.01.org/0day-ci/archive/20241104/202411041559.WIfxRN6n-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411041559.WIfxRN6n-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c:12:10: sparse: sparse: symbol 'link_rate_map' was not declared. Should it be static?

vim +/link_rate_map +12 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c

    11	
  > 12	const u8 link_rate_map[] = {DP_LINK_BW_1_62, DP_LINK_BW_2_7,
    13				    DP_LINK_BW_5_4, DP_LINK_BW_8_1};
    14	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

On Fri, Nov 01, 2024 at 06:50:26PM +0800, Yongbang Shi wrote:
> From: baihan li <libaihan@huawei.com>
> 
> Add link training process functions in this moduel.
> 
> Signed-off-by: baihan li <libaihan@huawei.com>
> Signed-off-by: yongbang shi <shiyongbang@huawei.com>
> ---
> Changelog:
> v2 -> v3:
>   - using switchcase in dp_link_reduce_lane, suggested by Dmitry Baryshkov.
>   - deleting dp_link_pattern2dpcd function and using macros directly, suggested by Dmitry Baryshkov.
>   - deleting EFAULT error codes, suggested by Dmitry Baryshkov.
> v1 -> v2:
>   - using drm_dp_* functions implement dp link training process, suggested by Jani Nikula.
>   - fix build errors reported by kernel test robot <lkp@intel.com>
>     Closes: https://lore.kernel.org/oe-kbuild-all/202410031735.8iRZZR6T-lkp@intel.com/
>   v1:https://lore.kernel.org/all/20240930100610.782363-1-shiyongbang@huawei.com/
> ---
>  drivers/gpu/drm/hisilicon/hibmc/Makefile     |   2 +-
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c | 346 +++++++++++++++++++
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h |  25 ++
>  drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h  |   8 +
>  4 files changed, 380 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
>  create mode 100644 drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h
> 
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/Makefile b/drivers/gpu/drm/hisilicon/hibmc/Makefile
> index 8770ec6dfffd..94d77da88bbf 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/Makefile
> +++ b/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
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
> new file mode 100644
> index 000000000000..7146de020c93
> --- /dev/null
> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c
> @@ -0,0 +1,346 @@
> +// 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"
> +#include "dp_link.h"
> +#include "dp_aux.h"
> +
> +const u8 link_rate_map[] = {DP_LINK_BW_1_62, DP_LINK_BW_2_7,
> +			    DP_LINK_BW_5_4, DP_LINK_BW_8_1};

hibmc_dp_link_rate_map[]

> +
> +static int hibmc_dp_link_training_configure(struct dp_dev *dp)
> +{
> +	u8 buf[2];
> +	int ret;
> +
> +	/* DP 2 lane */
> +	dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_LANE_DATA_EN,
> +			   dp->link.cap.lanes == DP_LANE_NUM_2 ? 0x3 : 0x1);
> +	dp_reg_write_field(dp->base + DP_DPTX_GCTL0, DP_CFG_PHY_LANE_NUM,
> +			   dp->link.cap.lanes == DP_LANE_NUM_2 ? 0x1 : 0);
> +
> +	/* enhanced frame */
> +	dp_reg_write_field(dp->base + DP_VIDEO_CTRL, DP_CFG_STREAM_FRAME_MODE, 0x1);
> +
> +	/* set rate and lane count */
> +	buf[0] = hibmc_dp_get_link_rate(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] = 0x10;
> +	buf[1] = 0x1;
> +	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 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;
> +		dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_SCRAMBLE_EN, 0x1);
> +	} else {
> +		dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, DP_CFG_SCRAMBLE_EN, 0);
> +	}
> +
> +	switch (pattern) {
> +	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:
> +		val = 0;

return -EINVAL?

> +	}
> +
> +	dp_reg_write_field(dp->base + DP_PHYIF_CTRL0, 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 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 dp_dev *dp, u8 lane_status[DP_LINK_STATUS_SIZE])
> +{
> +	u8 pre_emph[DP_LANE_NUM_MAX] = {0};
> +	u8 voltage[DP_LANE_NUM_MAX] = {0};
> +	bool changed = false;
> +	u8 train_set;
> +	u8 lane;
> +
> +	for (lane = 0; lane < dp->link.cap.lanes; lane++) {
> +		voltage[lane] = drm_dp_get_adjust_request_voltage(lane_status, lane);
> +		pre_emph[lane] = drm_dp_get_adjust_request_pre_emphasis(lane_status, lane);

train_set[lane] = drm_dp_get_adjust_request_voltage() |
                  drm_dp_get_adjust_request_pre_emphasis();

> +	}
> +
> +	for (lane = 0; lane < dp->link.cap.lanes; lane++) {
> +		train_set = voltage[lane] | pre_emph[lane];
> +		if (dp->link.train_set[lane] != train_set) {
> +			changed = true;
> +			dp->link.train_set[lane] = train_set;
> +		}
> +	}

	if (memcmp(dp->link.train_set, train_set)) {
		memcpy(dp->link.train_set, train_set);
		return true;
	}

	return false;

> +
> +	return changed;
> +}
> +
> +u8 hibmc_dp_get_link_rate(u8 index)
> +{
> +	return link_rate_map[index];
> +}
> +
> +static int hibmc_dp_link_reduce_rate(struct dp_dev *dp)
> +{
> +	if (dp->link.cap.link_rate > 0) {
> +		dp->link.cap.link_rate--;
> +		return 0;
> +	}
> +
> +	drm_err(dp->dev, "dp link training reduce rate failed, already lowest rate\n");
> +
> +	return -ELNRNG;

Link number out of range? Just -EIO or -EINVAL

> +}
> +
> +static int hibmc_dp_link_reduce_lane(struct dp_dev *dp)
> +{
> +	switch (dp->link.cap.lanes) {
> +	case DP_LANE_NUM_2:
> +		dp->link.cap.lanes--;
> +		break;
> +	case DP_LANE_NUM_1:
> +		drm_err(dp->dev, "dp link training reduce lane failed, already reach minimum\n");
> +		return -ELNRNG;
> +	}
> +
> +	return 0;
> +}
> +
> +static int hibmc_dp_link_training_cr(struct dp_dev *dp)
> +{
> +	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
> +	bool level_changed;
> +	u32 voltage_tries;
> +	u32 cr_tries;
> +	u32 max_cr;
> +	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)
> +	 */
> +	max_cr = dp->link.cap.rx_dpcd_revision >= DP_DPCD_REV_14 ? 10 : 80;
> +
> +	voltage_tries = 1;
> +	for (cr_tries = 0; cr_tries < max_cr; 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_info(dp->dev, "dp link training cr done\n");
> +			dp->link.status.clock_recovered = true;
> +			return 0;
> +		}
> +
> +		if (voltage_tries == 5) {
> +			drm_info(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 %u timers failed\n", max_cr);
> +	dp->link.status.clock_recovered = false;
> +
> +	return 0;
> +}
> +
> +static int hibmc_dp_link_training_channel_eq(struct dp_dev *dp)
> +{
> +	u8 lane_status[DP_LINK_STATUS_SIZE] = {0};
> +	u8 eq_tries;
> +	int tps;
> +	int ret;
> +
> +	if (dp->link.cap.is_tps4)
> +		tps = DP_TRAINING_PATTERN_4;
> +	else if (dp->link.cap.is_tps3)
> +		tps = DP_TRAINING_PATTERN_3;
> +	else
> +		tps = DP_TRAINING_PATTERN_2;
> +
> +	ret = hibmc_dp_link_set_pattern(dp, tps);
> +	if (ret)
> +		return ret;
> +
> +	for (eq_tries = 0; eq_tries < 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_info(dp->dev, "clock recovery check failed\n");
> +			drm_info(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_info(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 == 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 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 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 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;
> +}
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h
> new file mode 100644
> index 000000000000..b4958d122083
> --- /dev/null
> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.h
> @@ -0,0 +1,25 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/* Copyright (c) 2024 Hisilicon Limited. */
> +
> +#ifndef DP_LINK_H
> +#define DP_LINK_H
> +
> +#include "dp_comm.h"
> +
> +#define DP_LANE_NUM_MAX		2
> +#define DP_LANE_STATUS_SIZE	1

unused

> +#define DP_LANE_NUM_1		0x1
> +#define DP_LANE_NUM_2		0x2

Are you sure that you need to define 1 and 2? It's not like cap.lanes
requires a define to be understood.

> +
> +enum dp_pattern_e {
> +	DP_PATTERN_NO = 0,
> +	DP_PATTERN_TPS1,
> +	DP_PATTERN_TPS2,
> +	DP_PATTERN_TPS3,
> +	DP_PATTERN_TPS4,
> +};

Unused

> +
> +int hibmc_dp_link_training(struct dp_dev *dp);
> +u8 hibmc_dp_get_link_rate(u8 index);
> +
> +#endif
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
> index 83cf0cc06ae2..1032f6cde761 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
> +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_reg.h
> @@ -12,16 +12,24 @@
>  #define DP_AUX_RD_DATA0			0x64
>  #define DP_AUX_REQ			0x74
>  #define DP_AUX_STATUS			0x78
> +#define DP_PHYIF_CTRL0			0xa0
> +#define DP_VIDEO_CTRL			0x100
>  #define DP_DPTX_RST_CTRL		0x700
> +#define DP_DPTX_GCTL0			0x708
>  
>  #define DP_CFG_AUX_SYNC_LEN_SEL			BIT(1)
>  #define DP_CFG_AUX_TIMER_TIMEOUT		BIT(2)
> +#define DP_CFG_STREAM_FRAME_MODE		BIT(6)
>  #define DP_CFG_AUX_MIN_PULSE_NUM		GENMASK(13, 9)
> +#define DP_CFG_LANE_DATA_EN			GENMASK(11, 8)
> +#define DP_CFG_PHY_LANE_NUM			GENMASK(2, 1)
>  #define DP_CFG_AUX_REQ				BIT(0)
>  #define DP_CFG_AUX_RST_N			BIT(4)
>  #define DP_CFG_AUX_TIMEOUT			BIT(0)
>  #define DP_CFG_AUX_READY_DATA_BYTE		GENMASK(16, 12)
>  #define DP_CFG_AUX				GENMASK(24, 17)
>  #define DP_CFG_AUX_STATUS			GENMASK(11, 4)
> +#define DP_CFG_SCRAMBLE_EN			BIT(0)
> +#define DP_CFG_PAT_SEL				GENMASK(7, 4)
>  
>  #endif
> -- 
> 2.33.0
> 

-- 
With best wishes
Dmitry