Re: [PATCH v6 6/8] drm/i915/lobf: Check for sink error and disable LOBF

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Thu, 2025-03-20 at 00:45 +0530, Animesh Manna wrote:
> Disable LOBF/ALPM for any erroneous condition from sink side.
> 
> v1: Initial version.
> v2: Add centralized alpm error handling. [Jouni]
> v3: Improve debug print. [Jouni]
> 
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_alpm.c | 27
> +++++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_alpm.h |  1 +
>  drivers/gpu/drm/i915/display/intel_dp.c   |  3 +++
>  drivers/gpu/drm/i915/display/intel_psr.c  | 18 ++-------------
>  4 files changed, 33 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> b/drivers/gpu/drm/i915/display/intel_alpm.c
> index dc24772743b8..562f7269a583 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> @@ -496,4 +496,31 @@ void intel_alpm_disable(struct intel_dp
> *intel_dp)
>  	intel_de_rmw(display,
>  		     PORT_ALPM_CTL(cpu_transcoder),
>  		     PORT_ALPM_CTL_ALPM_AUX_LESS_ENABLE, 0);
> +
> +	drm_dbg_kms(display->drm, "Disabling ALPM\n");
> +}
> +
> +bool intel_alpm_get_error(struct intel_dp *intel_dp)
> +{
> +	struct intel_display *display = to_intel_display(intel_dp);
> +	struct drm_dp_aux *aux = &intel_dp->aux;
> +	u8 val;
> +	int r;
> +
> +	r = drm_dp_dpcd_readb(aux, DP_RECEIVER_ALPM_STATUS, &val);
> +	if (r != 1) {
> +		drm_err(display->drm, "Error reading ALPM
> status\n");
> +		return true;
> +	}
> +
> +	if (val & DP_ALPM_LOCK_TIMEOUT_ERROR) {
> +		drm_dbg_kms(display->drm,
> +			    "ALPM lock timeout error\n");
> +
> +		/* Clearing error */
> +		drm_dp_dpcd_writeb(aux, DP_RECEIVER_ALPM_STATUS,
> val);
> +		return true;
> +	}
> +
> +	return false;
>  }
> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.h
> b/drivers/gpu/drm/i915/display/intel_alpm.h
> index 91f51fb24f98..2f1fb82c0aac 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.h
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.h
> @@ -29,4 +29,5 @@ void intel_alpm_lobf_debugfs_add(struct
> intel_connector *connector);
>  bool intel_alpm_aux_wake_supported(struct intel_dp *intel_dp);
>  bool intel_alpm_aux_less_wake_supported(struct intel_dp *intel_dp);
>  void intel_alpm_disable(struct intel_dp *intel_dp);
> +bool intel_alpm_get_error(struct intel_dp *intel_dp);
>  #endif
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index a236b5fc7a3d..3f0fa2238afa 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5358,6 +5358,9 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)

>  	intel_psr_short_pulse(intel_dp);
>  
> +	if (intel_alpm_get_error(intel_dp))
> +		intel_alpm_disable(intel_dp);
> +

Maybe you want that error to have more permanent impact? This way LOBF
gets re-enabled?

BR,
Jouni Högander

>  	if (intel_dp_test_short_pulse(intel_dp))
>  		reprobe_needed = true;
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> b/drivers/gpu/drm/i915/display/intel_psr.c
> index 1d202f2eb356..09d440084671 100644
> --- a/drivers/gpu/drm/i915/display/intel_psr.c
> +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> @@ -3405,29 +3405,15 @@ static int
> psr_get_status_and_error_status(struct intel_dp *intel_dp,
>  
>  static void psr_alpm_check(struct intel_dp *intel_dp)
>  {
> -	struct intel_display *display = to_intel_display(intel_dp);
> -	struct drm_dp_aux *aux = &intel_dp->aux;
>  	struct intel_psr *psr = &intel_dp->psr;
> -	u8 val;
> -	int r;
>  
>  	if (!psr->sel_update_enabled)
>  		return;
>  
> -	r = drm_dp_dpcd_readb(aux, DP_RECEIVER_ALPM_STATUS, &val);
> -	if (r != 1) {
> -		drm_err(display->drm, "Error reading ALPM
> status\n");
> -		return;
> -	}
> -
> -	if (val & DP_ALPM_LOCK_TIMEOUT_ERROR) {
> +	if (intel_alpm_get_error(intel_dp)) {
>  		intel_psr_disable_locked(intel_dp);
>  		psr->sink_not_reliable = true;
> -		drm_dbg_kms(display->drm,
> -			    "ALPM lock timeout error, disabling
> PSR\n");
> -
> -		/* Clearing error */
> -		drm_dp_dpcd_writeb(aux, DP_RECEIVER_ALPM_STATUS,
> val);
> +		intel_alpm_disable(intel_dp);
>  	}
>  }
>