[Intel-gfx] [PATCH 4/7] drm/i915: Factor out a helper to disable the DPCD training pattern

[Ville Syrjälä]

On Tue, Sep 22, 2020 at 03:51:03PM +0300, Imre Deak wrote:
> To prepare for a follow-up LTTPR change factor out a helper to disable
> the training pattern in DPCD. We'll need to do this for each LTTPR
> (without programming the port to output the idle pattern) when training
> in LTTPR non-transparent mode.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  .../drm/i915/display/intel_dp_link_training.c | 28 +++++++++++--------
>  1 file changed, 16 insertions(+), 12 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 0c3809891bd2..6994a32244dc 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -102,30 +102,34 @@ void intel_dp_get_adjust_train(struct intel_dp *intel_dp,
>  		intel_dp->train_set[lane] = v | p;
>  }
>  
> +static bool intel_dp_disable_dpcd_training_pattern(struct intel_dp *intel_dp)
> +{
> +	u8 val = DP_TRAINING_PATTERN_DISABLE;
> +
> +	return drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET, &val, 1) == 1;
> +}


> +
>  static bool
>  intel_dp_set_link_train(struct intel_dp *intel_dp,
>  			u8 dp_train_pat)
>  {
>  	u8 buf[sizeof(intel_dp->train_set) + 1];
> -	int ret, len;
> +	int len;
>  
>  	intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
>  
> -	buf[0] = dp_train_pat;
>  	if ((dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) ==
> -	    DP_TRAINING_PATTERN_DISABLE) {
> +	    DP_TRAINING_PATTERN_DISABLE)
>  		/* don't write DP_TRAINING_LANEx_SET on disable */

As mentioned in the other patch I think we're doing things in the wrong
order here. I suspect it'll be cleaner to just stop doing
intel_dp_set_link_train(DISABLE) entirely and just have a dedicated
function for disabling link training. We can then trivially do a
followup to swap the order of operations to match the spec.

> -		len = 1;
> -	} else {
> -		/* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
> -		memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
> -		len = intel_dp->lane_count + 1;
> -	}
> +		return intel_dp_disable_dpcd_training_pattern(intel_dp);
>  
> -	ret = drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
> -				buf, len);
> +	buf[0] = dp_train_pat;
> +	/* DP_TRAINING_LANEx_SET follow DP_TRAINING_PATTERN_SET */
> +	memcpy(buf + 1, intel_dp->train_set, intel_dp->lane_count);
> +	len = intel_dp->lane_count + 1;
>  
> -	return ret == len;
> +	return drm_dp_dpcd_write(&intel_dp->aux, DP_TRAINING_PATTERN_SET,
> +				 buf, len) == len;
>  }
>  
>  static bool
> -- 
> 2.17.1
> 
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-- 
Ville Syrjälä
Intel