Re: [PATCH v5 5/6] drm/i915/dp: Queue a link check after link training is complete

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 04 Mar 2025, Imre Deak <imre.deak@intel.com> wrote:
> After link training - both in case of a passing and failing LT result -
> a work is scheduled to check the link state. This check should take
> place after the link training is completed by disabling the link
> training pattern and setting intel_dp::link_trained=true. Atm, the work
> is scheduled before these steps, which may result in checking the link
> state too early (and thus not retraining the link as expected).
>
> Fix the above by scheduling the link check work after link training is
> complete.
>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  .../gpu/drm/i915/display/intel_dp_link_training.c   | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> 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 3906c11acc968..c1be073b9fc48 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -1110,6 +1110,7 @@ intel_dp_128b132b_intra_hop(struct intel_dp *intel_dp,
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp,
>  			      const struct intel_crtc_state *crtc_state)
>  {
> +	struct intel_display *display = to_intel_display(intel_dp);
>  	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
>  
>  	intel_dp->link_trained = true;

Side note, it's a bit misleading that we set this even if link training
failed... but we probably depend on it.

> @@ -1124,6 +1125,13 @@ void intel_dp_stop_link_train(struct intel_dp *intel_dp,
>  	}
>  
>  	intel_hpd_unblock(encoder);
> +
> +	if (!display->hotplug.ignore_long_hpd &&

We already poke at this directly elsewhere in the file, but I'm not a
fan of doing so. We should have a function and use that. The fact that
we can do anything doesn't mean we should.

I guess that's for another patch, another time.

> +	    intel_dp->link.seq_train_failures < 2) {

It's not great that the magic 2 is duplicated. It was fine in one place.

Regardless,

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


> +		int delay_ms = intel_dp->link.seq_train_failures ? 0 : 2000;
> +
> +		intel_encoder_link_check_queue_work(encoder, delay_ms);
> +	}
>  }
>  
>  static bool
> @@ -1628,7 +1636,6 @@ void intel_dp_start_link_train(struct intel_atomic_state *state,
>  		lt_dbg(intel_dp, DP_PHY_DPRX, "Forcing link training failure\n");
>  	} else if (passed) {
>  		intel_dp->link.seq_train_failures = 0;
> -		intel_encoder_link_check_queue_work(encoder, 2000);
>  		return;
>  	}
>  
> @@ -1651,10 +1658,8 @@ void intel_dp_start_link_train(struct intel_atomic_state *state,
>  		return;
>  	}
>  
> -	if (intel_dp->link.seq_train_failures < 2) {
> -		intel_encoder_link_check_queue_work(encoder, 0);
> +	if (intel_dp->link.seq_train_failures < 2)
>  		return;
> -	}
>  
>  	if (intel_dp_schedule_fallback_link_training(state, intel_dp, crtc_state))



>  		return;

-- 
Jani Nikula, Intel