[Intel-gfx] [PATCH 1/7] drm/i915: Fix DP link training pattern mask

[Ville Syrjälä]

On Tue, Sep 22, 2020 at 03:51:00PM +0300, Imre Deak wrote:
> An LTTPR can be trained with training pattern 4 even if the DPCD
> revision is < 1.4, but drm_dp_training_pattern_mask() would change
> pattern 4 to pattern 3 on those DPCD revisions.
> 
> Since intel_dp_training_pattern() makes already sure that the proper
> training pattern is used, all that needs to be masked out is the
> scrambling disable flag, which is or'd to the mask later based on the
> training pattern.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c              |  3 +--
>  drivers/gpu/drm/i915/display/intel_dp.c               | 10 +++++-----
>  drivers/gpu/drm/i915/display/intel_dp_link_training.c |  2 +-
>  3 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 4d06178cd76c..946a3b6f2d10 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -4158,13 +4158,12 @@ static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
>  				     u8 dp_train_pat)
>  {
>  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> -	u8 train_pat_mask = drm_dp_training_pattern_mask(intel_dp->dpcd);
>  	u32 temp;
>  
>  	temp = intel_de_read(dev_priv, intel_dp->regs.dp_tp_ctl);
>  
>  	temp &= ~DP_TP_CTL_LINK_TRAIN_MASK;
> -	switch (dp_train_pat & train_pat_mask) {
> +	switch (dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) {

Maybe introduce a helper to do the masking for us?

Anyways
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

>  	case DP_TRAINING_PATTERN_DISABLE:
>  		temp |= DP_TP_CTL_LINK_TRAIN_NORMAL;
>  		break;
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index bf1e9cf1c0f3..2a4a9c0e7427 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -3778,7 +3778,7 @@ cpt_set_link_train(struct intel_dp *intel_dp,
>  
>  	*DP &= ~DP_LINK_TRAIN_MASK_CPT;
>  
> -	switch (dp_train_pat & DP_TRAINING_PATTERN_MASK) {
> +	switch (dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) {
>  	case DP_TRAINING_PATTERN_DISABLE:
>  		*DP |= DP_LINK_TRAIN_OFF_CPT;
>  		break;
> @@ -3808,7 +3808,7 @@ g4x_set_link_train(struct intel_dp *intel_dp,
>  
>  	*DP &= ~DP_LINK_TRAIN_MASK;
>  
> -	switch (dp_train_pat & DP_TRAINING_PATTERN_MASK) {
> +	switch (dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) {
>  	case DP_TRAINING_PATTERN_DISABLE:
>  		*DP |= DP_LINK_TRAIN_OFF;
>  		break;
> @@ -4498,12 +4498,12 @@ intel_dp_program_link_training_pattern(struct intel_dp *intel_dp,
>  				       u8 dp_train_pat)
>  {
>  	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> -	u8 train_pat_mask = drm_dp_training_pattern_mask(intel_dp->dpcd);
>  
> -	if (dp_train_pat & train_pat_mask)
> +	if ((dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) !=
> +	    DP_TRAINING_PATTERN_DISABLE)
>  		drm_dbg_kms(&dev_priv->drm,
>  			    "Using DP training pattern TPS%d\n",
> -			    dp_train_pat & train_pat_mask);
> +			    dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE);
>  
>  	intel_dp->set_link_train(intel_dp, dp_train_pat);
>  }
> 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 f2c8b56be9ea..f8b53c5b5777 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -96,7 +96,7 @@ intel_dp_set_link_train(struct intel_dp *intel_dp,
>  	intel_dp_program_link_training_pattern(intel_dp, dp_train_pat);
>  
>  	buf[0] = dp_train_pat;
> -	if ((dp_train_pat & DP_TRAINING_PATTERN_MASK) ==
> +	if ((dp_train_pat & ~DP_LINK_SCRAMBLING_DISABLE) ==
>  	    DP_TRAINING_PATTERN_DISABLE) {
>  		/* don't write DP_TRAINING_LANEx_SET on disable */
>  		len = 1;
> -- 
> 2.17.1
> 
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-- 
Ville Syrjälä
Intel