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

[Manna, Animesh]

> -----Original Message-----
> From: Hogander, Jouni <jouni.hogander at intel.com>
> Sent: Monday, March 24, 2025 1:23 PM
> To: intel-xe at lists.freedesktop.org; Manna, Animesh
> <animesh.manna at intel.com>; intel-gfx at lists.freedesktop.org
> Cc: Nikula, Jani <jani.nikula at intel.com>; B, Jeevan <jeevan.b at intel.com>
> Subject: Re: [PATCH v6 6/8] drm/i915/lobf: Check for sink error and disable
> LOBF
> 
> 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 at 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?

I felt sink can recover, can be sometime cable issue and permanently disabling may be not right.. 
But I don’t have any strong opinion either way.. We can have error-counter and multiple error can lead to disabling permanently by setting the flag lobf_disable_debug. Still not very clear to me.
Any suggestion will be helpful.

Regards,
Animesh
> 
> 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);
> >  	}
> >  }
> >