Re: [PATCH v2 17/21] drm/i915/dp: Add debugfs entries to set a target link rate/lane count

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, May 20, 2024 at 09:58:15PM +0300, Imre Deak wrote:
> Add connector debugfs entries to set a target link rate/lane count to be
> used by a link training afterwards. After setting a target link
> rate/lane count reset the link training parameters and for a non-auto
> target disable reducing the link parameters via the fallback logic.  The
> former one can be used after testing link training failure scenarios
> - via debugfs entries added later - to reset the reduced link parameters
> after the test.
> 
> v2:
> - Add the entries from intel_dp_link_training.c (Jani)
> - Rename the entries to i915_dp_set_link_rate/lane_count.
> 
> Cc: Jani Nikula <jani.nikula@intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  |   2 +
>  .../drm/i915/display/intel_display_types.h    |   2 +
>  drivers/gpu/drm/i915/display/intel_dp.c       |  63 ++++-
>  drivers/gpu/drm/i915/display/intel_dp.h       |   2 +
>  .../drm/i915/display/intel_dp_link_training.c | 230 ++++++++++++++++++
>  .../drm/i915/display/intel_dp_link_training.h |   4 +
>  6 files changed, 294 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index 35f9f86ef70f4..f83ffa2534925 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -23,6 +23,7 @@
>  #include "intel_display_types.h"
>  #include "intel_dmc.h"
>  #include "intel_dp.h"
> +#include "intel_dp_link_training.h"
>  #include "intel_dp_mst.h"
>  #include "intel_drrs.h"
>  #include "intel_fbc.h"
> @@ -1515,6 +1516,7 @@ void intel_connector_debugfs_add(struct intel_connector *connector)
>  	intel_drrs_connector_debugfs_add(connector);
>  	intel_pps_connector_debugfs_add(connector);
>  	intel_psr_connector_debugfs_add(connector);
> +	intel_dp_link_training_debugfs_add(connector);
>  
>  	if (connector_type == DRM_MODE_CONNECTOR_DisplayPort ||
>  	    connector_type == DRM_MODE_CONNECTOR_HDMIA ||
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index eb0cac3e27acf..e1c41cece249d 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1765,6 +1765,8 @@ struct intel_dp {
>  		int max_lane_count;
>  		/* Max rate for the current link */
>  		int max_rate;
> +		int requested_lane_count;
> +		int requested_rate;

"requested" is perhaps a bit weak. Maybe "force" or "override"
although perhaps those might give the impression that it ignores
the sink limits or something?

>  		bool retrain_disabled;
>  		/* Sequential link training failures after a passing LT */
>  		int seq_train_failures;
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index c8d940a2ef7af..cf4a768fccd15 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -345,7 +345,7 @@ int intel_dp_max_common_rate(struct intel_dp *intel_dp)
>  	return intel_dp_common_rate(intel_dp, intel_dp->num_common_rates - 1);
>  }
>  
> -static int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
> +int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port)
>  {
>  	int vbt_max_lanes = intel_bios_dp_max_lane_count(dig_port->base.devdata);
>  	int max_lanes = dig_port->max_lanes;
> @@ -371,19 +371,39 @@ int intel_dp_max_common_lane_count(struct intel_dp *intel_dp)
>  	return min3(source_max, sink_max, lane_max);
>  }
>  
> +static int requested_lane_count(struct intel_dp *intel_dp)
> +{
> +	return clamp(intel_dp->link.requested_lane_count, 1, intel_dp_max_common_lane_count(intel_dp));
> +}
> +
>  int intel_dp_max_lane_count(struct intel_dp *intel_dp)
>  {
> -	switch (intel_dp->link.max_lane_count) {
> +	int lane_count;
> +
> +	if (intel_dp->link.requested_lane_count)
> +		lane_count = requested_lane_count(intel_dp);
> +	else
> +		lane_count = intel_dp->link.max_lane_count;
> +
> +	switch (lane_count) {
>  	case 1:
>  	case 2:
>  	case 4:
> -		return intel_dp->link.max_lane_count;
> +		return lane_count;
>  	default:
> -		MISSING_CASE(intel_dp->link.max_lane_count);
> +		MISSING_CASE(lane_count);
>  		return 1;
>  	}
>  }
>  
> +static int intel_dp_min_lane_count(struct intel_dp *intel_dp)
> +{
> +	if (intel_dp->link.requested_lane_count)
> +		return requested_lane_count(intel_dp);
> +
> +	return 1;
> +}
> +
>  /*
>   * The required data bandwidth for a mode with given pixel clock and bpp. This
>   * is the required net bandwidth independent of the data bandwidth efficiency.
> @@ -1306,16 +1326,38 @@ static void intel_dp_print_rates(struct intel_dp *intel_dp)
>  	drm_dbg_kms(&i915->drm, "common rates: %s\n", str);
>  }
>  
> +static int requested_rate(struct intel_dp *intel_dp)
> +{
> +	int len = intel_dp_common_len_rate_limit(intel_dp, intel_dp->link.requested_rate);
> +
> +	if (len == 0)
> +		return intel_dp_common_rate(intel_dp, 0);
> +
> +	return intel_dp_common_rate(intel_dp, len - 1);
> +}
> +
>  int
>  intel_dp_max_link_rate(struct intel_dp *intel_dp)
>  {
>  	int len;
>  
> +	if (intel_dp->link.requested_rate)
> +		return requested_rate(intel_dp);
> +
>  	len = intel_dp_common_len_rate_limit(intel_dp, intel_dp->link.max_rate);
>  
>  	return intel_dp_common_rate(intel_dp, len - 1);
>  }
>  
> +static int
> +intel_dp_min_link_rate(struct intel_dp *intel_dp)
> +{
> +	if (intel_dp->link.requested_rate)
> +		return requested_rate(intel_dp);
> +
> +	return intel_dp_common_rate(intel_dp, 0);
> +}
> +
>  int intel_dp_rate_select(struct intel_dp *intel_dp, int rate)
>  {
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> @@ -2285,13 +2327,14 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
>  			       bool dsc,
>  			       struct link_config_limits *limits)
>  {
> -	limits->min_rate = intel_dp_common_rate(intel_dp, 0);
> +	limits->min_rate = intel_dp_min_link_rate(intel_dp);
>  	limits->max_rate = intel_dp_max_link_rate(intel_dp);
>  
>  	/* FIXME 128b/132b SST support missing */
>  	limits->max_rate = min(limits->max_rate, 810000);
> +	limits->min_rate = min(limits->min_rate, limits->max_rate);
>  
> -	limits->min_lane_count = 1;
> +	limits->min_lane_count = intel_dp_min_lane_count(intel_dp);
>  	limits->max_lane_count = intel_dp_max_lane_count(intel_dp);
>  
>  	limits->pipe.min_bpp = intel_dp_min_bpp(crtc_state->output_format);
> @@ -2307,8 +2350,10 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
>  		 * configuration, and typically on older panels these
>  		 * values correspond to the native resolution of the panel.
>  		 */
> -		limits->min_lane_count = limits->max_lane_count;
> -		limits->min_rate = limits->max_rate;
> +		if (intel_dp->link.requested_lane_count == 0)
> +			limits->min_lane_count = limits->max_lane_count;
> +		if (intel_dp->link.requested_rate == 0)
> +			limits->min_rate = limits->max_rate;

Aren't the min and max the same anyway if the debugfs override is in
use?

>  	}
>  
>  	intel_dp_adjust_compliance_config(intel_dp, crtc_state, limits);
> @@ -2946,7 +2991,7 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  	intel_dp->lane_count = lane_count;
>  }
>  
> -static void intel_dp_reset_link_params(struct intel_dp *intel_dp)
> +void intel_dp_reset_link_params(struct intel_dp *intel_dp)
>  {
>  	intel_dp->link.max_lane_count = intel_dp_max_common_lane_count(intel_dp);
>  	intel_dp->link.max_rate = intel_dp_max_common_rate(intel_dp);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index 3fa53ac601d58..79914e5080251 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -99,6 +99,7 @@ void intel_edp_backlight_off(const struct drm_connector_state *conn_state);
>  void intel_edp_fixup_vbt_bpp(struct intel_encoder *encoder, int pipe_bpp);
>  void intel_dp_mst_suspend(struct drm_i915_private *dev_priv);
>  void intel_dp_mst_resume(struct drm_i915_private *dev_priv);
> +int intel_dp_max_source_lane_count(struct intel_digital_port *dig_port);
>  int intel_dp_max_link_rate(struct intel_dp *intel_dp);
>  int intel_dp_max_lane_count(struct intel_dp *intel_dp);
>  int intel_dp_config_required_rate(const struct intel_crtc_state *crtc_state);
> @@ -108,6 +109,7 @@ int intel_dp_max_common_lane_count(struct intel_dp *intel_dp);
>  int intel_dp_common_rate(struct intel_dp *intel_dp, int index);
>  int intel_dp_rate_index(const int *rates, int len, int rate);
>  void intel_dp_update_sink_caps(struct intel_dp *intel_dp);
> +void intel_dp_reset_link_params(struct intel_dp *intel_dp);
>  
>  void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
>  			   u8 *link_bw, u8 *rate_select);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index 9a59a28ca36d2..a6021e17cc1ef 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -1115,6 +1115,9 @@ static int reduce_link_rate(struct intel_dp *intel_dp, int current_rate)
>  	int rate_index;
>  	int new_rate;
>  
> +	if (intel_dp->link.requested_rate)
> +		return -1;
> +
>  	rate_index = intel_dp_rate_index(intel_dp->common_rates,
>  					 intel_dp->num_common_rates,
>  					 current_rate);
> @@ -1133,6 +1136,9 @@ static int reduce_link_rate(struct intel_dp *intel_dp, int current_rate)
>  
>  static int reduce_lane_count(struct intel_dp *intel_dp, int current_lane_count)
>  {
> +	if (intel_dp->link.requested_lane_count)
> +		return -1;
> +
>  	if (current_lane_count > 1)
>  		return current_lane_count >> 1;
>  
> @@ -1543,3 +1549,227 @@ void intel_dp_128b132b_sdp_crc16(struct intel_dp *intel_dp,
>  
>  	lt_dbg(intel_dp, DP_PHY_DPRX, "DP2.0 SDP CRC16 for 128b/132b enabled\n");
>  }
> +
> +static struct intel_dp *intel_connector_to_intel_dp(struct intel_connector *connector)
> +{
> +	if (connector->mst_port)
> +		return connector->mst_port;
> +	else
> +		return enc_to_intel_dp(intel_attached_encoder(connector));
> +}
> +
> +static int i915_dp_set_link_rate_show(struct seq_file *m, void *data)
> +{
> +	struct intel_connector *connector = to_intel_connector(m->private);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_dp *intel_dp;
> +	int ret;
> +	int i;
> +
> +	ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);

What is this lock protecting exactly?

> +	if (ret)
> +		return ret;
> +
> +	intel_dp = intel_connector_to_intel_dp(connector);
> +
> +	seq_printf(m, "%sauto%s",
> +		   intel_dp->link.requested_rate == 0 ? "[" : "",
> +		   intel_dp->link.requested_rate == 0 ? "]" : "");
> +
> +	for (i = 0; i < intel_dp->num_source_rates; i++)
> +		seq_printf(m, " %s%d%s%s",
> +			   intel_dp->source_rates[i] == intel_dp->link.requested_rate ? "[" : "",
> +			   intel_dp->source_rates[i],
> +			   intel_dp->link_trained &&
> +				intel_dp->source_rates[i] == intel_dp->link_rate ? "*" : "",
> +			   intel_dp->source_rates[i] == intel_dp->link.requested_rate ? "]" : "");
> +
> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +	seq_putc(m, '\n');
> +
> +	return 0;
> +}
> +
> +static int parse_link_rate(struct intel_dp *intel_dp, const char __user *ubuf, size_t len)
> +{
> +	char *kbuf;
> +	const char *p;
> +	int rate;
> +	int ret = 0;
> +
> +	kbuf = memdup_user_nul(ubuf, len);
> +	if (IS_ERR(kbuf))
> +		return PTR_ERR(kbuf);
> +
> +	p = strim(kbuf);
> +
> +	if (!strcmp(p, "auto")) {
> +		rate = 0;
> +	} else {
> +		ret = kstrtoint(p, 0, &rate);
> +		if (ret < 0)
> +			goto out_free;
> +
> +		if (intel_dp_rate_index(intel_dp->source_rates,
> +					intel_dp->num_source_rates,
> +					rate) < 0)
> +			ret = -EINVAL;
> +	}
> +
> +out_free:
> +	kfree(kbuf);
> +
> +	return ret < 0 ? ret : rate;
> +}
> +
> +static ssize_t i915_dp_set_link_rate_write(struct file *file,
> +					   const char __user *ubuf,
> +					   size_t len, loff_t *offp)
> +{
> +	struct seq_file *m = file->private_data;
> +	struct intel_connector *connector = to_intel_connector(m->private);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_dp *intel_dp = intel_connector_to_intel_dp(connector);
> +	int rate;
> +	int ret;
> +
> +	ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
> +	if (ret)
> +		return ret;
> +
> +	intel_dp = intel_connector_to_intel_dp(connector);
> +
> +	rate = parse_link_rate(intel_dp, ubuf, len);
> +	if (rate < 0) {
> +		drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +		return rate;
> +	}
> +
> +	intel_dp_reset_link_params(intel_dp);
> +	intel_dp->link.requested_rate = rate;
> +
> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +	*offp += len;
> +
> +	return len;
> +}
> +DEFINE_SHOW_STORE_ATTRIBUTE(i915_dp_set_link_rate);
> +
> +static int i915_dp_set_lane_count_show(struct seq_file *m, void *data)
> +{
> +	struct intel_connector *connector = to_intel_connector(m->private);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_dp *intel_dp;
> +	int ret;
> +	int i;
> +
> +	ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
> +	if (ret)
> +		return ret;
> +
> +	intel_dp = intel_connector_to_intel_dp(connector);
> +
> +	seq_printf(m, "%sauto%s",
> +		   intel_dp->link.requested_lane_count == 0 ? "[" : "",
> +		   intel_dp->link.requested_lane_count == 0 ? "]" : "");
> +
> +	for (i = 1; i <= 4; i <<= 1)
> +		seq_printf(m, " %s%d%s%s",
> +			   i == intel_dp->link.requested_lane_count ? "[" : "",
> +			   i,
> +			   intel_dp->link_trained &&
> +				i == intel_dp->lane_count ? "*" : "",
> +			   i == intel_dp->link.requested_lane_count ? "]" : "");
> +
> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +	seq_putc(m, '\n');
> +
> +	return 0;
> +}
> +
> +static int parse_lane_count(const char __user *ubuf, size_t len)
> +{
> +	char *kbuf;
> +	const char *p;
> +	int lane_count;
> +	int ret = 0;
> +
> +	kbuf = memdup_user_nul(ubuf, len);
> +	if (IS_ERR(kbuf))
> +		return PTR_ERR(kbuf);
> +
> +	p = strim(kbuf);
> +
> +	if (!strcmp(p, "auto")) {
> +		lane_count = 0;
> +	} else {
> +		ret = kstrtoint(p, 0, &lane_count);
> +		if (ret < 0)
> +			goto out_free;
> +
> +		switch (lane_count) {
> +		case 1:
> +		case 2:
> +		case 4:
> +			break;
> +		default:
> +			ret = -EINVAL;
> +		}
> +	}
> +
> +out_free:
> +	kfree(kbuf);
> +
> +	return ret < 0 ? ret : lane_count;
> +}
> +
> +static ssize_t i915_dp_set_lane_count_write(struct file *file,
> +					    const char __user *ubuf,
> +					    size_t len, loff_t *offp)
> +{
> +	struct seq_file *m = file->private_data;
> +	struct intel_connector *connector = to_intel_connector(m->private);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_dp *intel_dp;
> +	int lane_count;
> +	int ret;
> +
> +	lane_count = parse_lane_count(ubuf, len);
> +	if (lane_count < 0)
> +		return lane_count;
> +
> +	ret = drm_modeset_lock_single_interruptible(&i915->drm.mode_config.connection_mutex);
> +	if (ret)
> +		return ret;
> +
> +	intel_dp = intel_connector_to_intel_dp(connector);
> +
> +	intel_dp_reset_link_params(intel_dp);
> +	intel_dp->link.requested_lane_count = lane_count;
> +
> +	drm_modeset_unlock(&i915->drm.mode_config.connection_mutex);
> +
> +	*offp += len;
> +
> +	return len;
> +}
> +DEFINE_SHOW_STORE_ATTRIBUTE(i915_dp_set_lane_count);
> +
> +void intel_dp_link_training_debugfs_add(struct intel_connector *connector)
> +{
> +	struct dentry *root = connector->base.debugfs_entry;
> +
> +	if (connector->base.connector_type != DRM_MODE_CONNECTOR_DisplayPort &&
> +	    connector->base.connector_type != DRM_MODE_CONNECTOR_eDP)
> +		return;
> +
> +	debugfs_create_file("i915_dp_set_link_rate", 0644, root,
> +			    connector, &i915_dp_set_link_rate_fops);
> +
> +	debugfs_create_file("i915_dp_set_lane_count", 0644, root,
> +			    connector, &i915_dp_set_lane_count_fops);
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.h b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> index f658230960333..42e7fc6cb171a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.h
> @@ -9,6 +9,7 @@
>  #include <drm/display/drm_dp_helper.h>
>  
>  struct intel_atomic_state;
> +struct intel_connector;
>  struct intel_crtc_state;
>  struct intel_dp;
>  
> @@ -44,4 +45,7 @@ static inline u8 intel_dp_training_pattern_symbol(u8 pattern)
>  
>  void intel_dp_128b132b_sdp_crc16(struct intel_dp *intel_dp,
>  				 const struct intel_crtc_state *crtc_state);
> +
> +void intel_dp_link_training_debugfs_add(struct intel_connector *connector);
> +
>  #endif /* __INTEL_DP_LINK_TRAINING_H__ */
> -- 
> 2.43.3

-- 
Ville Syrjälä
Intel