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

Imre Deak
2024-05-23T16:15:53Z

On Thu, May 23, 2024 at 06:25:08PM +0300, Ville Syrjälä wrote:
> 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?

It determines the rate/lane count within the valid common range. Can
rename it to force.

>
> > 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?

Yes, thanks for spotting that, this eDP override can stay as-is.

> > }
> >
> > 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?

The connector state, for instace from getting removed after a disconnect
event and the link caps in intel_dp.

>
> > + 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