Re: [PATCH 1/5] drm/i915/dp: Add helpers to reset link params

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

On Mon, May 18, 2026 at 02:24:22PM +0300, Imre Deak wrote:
> Add helpers to defer and handle link params resets instead of
> open-coding the same. Rename intel_dp_reset_link_params() to
> intel_dp_reset_link_params_force() to align its name with the new
> deferred reset helpers.
> 
> When deferring a reset, return whether a new reset was queued, used by a
> follow-up change.
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/display/g4x_dp.c         |  2 +-
>  drivers/gpu/drm/i915/display/intel_ddi.c      |  2 +-
>  drivers/gpu/drm/i915/display/intel_dp.c       | 41 +++++++++++++++----
>  drivers/gpu/drm/i915/display/intel_dp.h       |  3 +-
>  .../drm/i915/display/intel_dp_link_training.c |  4 +-
>  5 files changed, 38 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/g4x_dp.c b/drivers/gpu/drm/i915/display/g4x_dp.c
> index 5ff1cdf4581a5..c20a97e21419b 100644
> --- a/drivers/gpu/drm/i915/display/g4x_dp.c
> +++ b/drivers/gpu/drm/i915/display/g4x_dp.c
> @@ -1265,7 +1265,7 @@ static void intel_dp_encoder_reset(struct drm_encoder *encoder)
>  
>  	intel_dp->DP = intel_de_read(display, intel_dp->output_reg);
>  
> -	intel_dp->reset_link_params = true;
> +	intel_dp_reset_link_params_defer(intel_dp);
>  	intel_dp_invalidate_source_oui(intel_dp);
>  
>  	if (display->platform.valleyview || display->platform.cherryview)
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 86520848892e0..77819aaeccb76 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -4664,7 +4664,7 @@ static void intel_ddi_encoder_reset(struct drm_encoder *encoder)
>  	struct intel_dp *intel_dp = enc_to_intel_dp(to_intel_encoder(encoder));
>  	struct intel_digital_port *dig_port = enc_to_dig_port(to_intel_encoder(encoder));
>  
> -	intel_dp->reset_link_params = true;
> +	intel_dp_reset_link_params_defer(intel_dp);
>  	intel_dp_invalidate_source_oui(intel_dp);
>  
>  	intel_pps_encoder_reset(intel_dp);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 1920d2f026665..13163dd085e91 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -3710,7 +3710,11 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  	intel_dp->lane_count = lane_count;
>  }
>  
> -void intel_dp_reset_link_params(struct intel_dp *intel_dp)
> +/*
> + * Reset link params now, preserving any deferred connector
> + * detect-time reset request.
> + */
> +void intel_dp_reset_link_params_force(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);
> @@ -3720,6 +3724,28 @@ void intel_dp_reset_link_params(struct intel_dp *intel_dp)
>  	intel_dp->link.seq_train_failures = 0;
>  }
>  
> +/*
> + * Reset link params during the next connector detect.
> + * Return %true if a new reset was queued.
> + */
> +bool intel_dp_reset_link_params_defer(struct intel_dp *intel_dp)

I find the intel_dp_reset_link_params_defer() vs.
intel_dp_reset_link_params_force() naming rather confusing.

Can't immediately think of a really good name for
intel_dp_reset_link_params_defer() so maybe it's better to not
have a function for it at all (ie. just drop this patch)? Then
you at least see that it's just setting the flag. AFAICS you
only have a single place (in the last patch) that uses this
return value for anything, so could just do the check+set
dance there on the spot.

> +{
> +	bool reset_was_pending = intel_dp->reset_link_params;
> +
> +	intel_dp->reset_link_params = true;
> +
> +	return !reset_was_pending;
> +}
> +
> +static void intel_dp_handle_deferred_link_params_reset(struct intel_dp *intel_dp)
> +{
> +	if (!intel_dp->reset_link_params)
> +		return;
> +
> +	intel_dp->reset_link_params = false;
> +	intel_dp_reset_link_params_force(intel_dp);
> +}
> +
>  /* Enable backlight PWM and backlight PP control. */
>  void intel_edp_backlight_on(const struct intel_crtc_state *crtc_state,
>  			    const struct drm_connector_state *conn_state)
> @@ -4066,7 +4092,7 @@ void intel_dp_sync_state(struct intel_encoder *encoder,
>  	intel_dp_tunnel_resume(intel_dp, crtc_state, dpcd_updated);
>  
>  	if (crtc_state) {
> -		intel_dp_reset_link_params(intel_dp);
> +		intel_dp_reset_link_params_force(intel_dp);
>  		intel_dp_set_link_params(intel_dp, crtc_state->port_clock, crtc_state->lane_count);
>  		intel_dp->link.active = true;
>  	}
> @@ -6487,10 +6513,7 @@ intel_dp_detect(struct drm_connector *_connector,
>  
>  	intel_dp_detect_sdp_caps(intel_dp);
>  
> -	if (intel_dp->reset_link_params) {
> -		intel_dp_reset_link_params(intel_dp);
> -		intel_dp->reset_link_params = false;
> -	}
> +	intel_dp_handle_deferred_link_params_reset(intel_dp);
>  
>  	intel_dp_mst_configure(intel_dp);
>  
> @@ -6944,7 +6967,7 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port, bool long_hpd)
>  
>  		intel_dp_read_dprx_caps(intel_dp, dpcd);
>  
> -		intel_dp->reset_link_params = true;
> +		intel_dp_reset_link_params_defer(intel_dp);
>  		intel_dp_invalidate_source_oui(intel_dp);
>  
>  		return IRQ_NONE;
> @@ -7252,7 +7275,7 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
>  		     encoder->base.name))
>  		return false;
>  
> -	intel_dp->reset_link_params = true;
> +	intel_dp_reset_link_params_defer(intel_dp);
>  
>  	/* Preserve the current hw state. */
>  	intel_dp->DP = intel_de_read(display, intel_dp->output_reg);
> @@ -7317,7 +7340,7 @@ intel_dp_init_connector(struct intel_digital_port *dig_port,
>  
>  	intel_dp_set_source_rates(intel_dp);
>  	intel_dp_set_common_rates(intel_dp);
> -	intel_dp_reset_link_params(intel_dp);
> +	intel_dp_reset_link_params_force(intel_dp);
>  
>  	/* init MST on ports that can support it */
>  	intel_dp_mst_encoder_init(dig_port, connector->base.base.id);
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
> index f41480d247142..7c24d3dbb6983 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.h
> +++ b/drivers/gpu/drm/i915/display/intel_dp.h
> @@ -114,7 +114,8 @@ int intel_dp_rate_index(const int *rates, int len, int rate);
>  int intel_dp_link_config_index(struct intel_dp *intel_dp, int link_rate, int lane_count);
>  void intel_dp_link_config_get(struct intel_dp *intel_dp, int idx, int *link_rate, int *lane_count);
>  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_reset_link_params_force(struct intel_dp *intel_dp);
> +bool intel_dp_reset_link_params_defer(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 a26094223f780..b7075060e7bd3 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -1935,7 +1935,7 @@ static ssize_t i915_dp_force_link_rate_write(struct file *file,
>  	if (err)
>  		return err;
>  
> -	intel_dp_reset_link_params(intel_dp);
> +	intel_dp_reset_link_params_force(intel_dp);
>  	intel_dp->link.force_rate = rate;
>  
>  	drm_modeset_unlock(&display->drm->mode_config.connection_mutex);
> @@ -2037,7 +2037,7 @@ static ssize_t i915_dp_force_lane_count_write(struct file *file,
>  	if (err)
>  		return err;
>  
> -	intel_dp_reset_link_params(intel_dp);
> +	intel_dp_reset_link_params_force(intel_dp);
>  	intel_dp->link.force_lane_count = lane_count;
>  
>  	drm_modeset_unlock(&display->drm->mode_config.connection_mutex);
> -- 
> 2.49.1

-- 
Ville Syrjälä
Intel