Re: [Intel-gfx] [PATCH 1/2] drm/i915/ddi: Don't frob the DP link scramble disabling flag

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Imre Deak <imre.deak@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 1/2] drm/i915/ddi: Don't frob the DP link scramble disabling flag
Date: Tue, 14 Jul 2020 19:05:32 +0300	[thread overview]
Message-ID: <20200714160532.GK6112@intel.com> (raw)
In-Reply-To: <20200714153141.10280-1-imre.deak@intel.com>

On Tue, Jul 14, 2020 at 06:31:40PM +0300, Imre Deak wrote:
> According to BSpec this flag should not be changed while the DDI
> function is enabled. On BDW+ the DP_TP_CTL register spec also states it
> explicitly that the HW takes care of enabling/disabling the scrambling
> for training patterns (and it must stay enabled for normal pixel
> output). Assume that this HW automatic handling of scrambling is also
> true for HSW.

It is at least marked as debug only for hsw.

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

> 
> BSpec: 8013, 7557, 50484
> 
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 2c484b55bcdf..c467f18d5e1b 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -4037,8 +4037,7 @@ static void intel_ddi_prepare_link_retrain(struct intel_dp *intel_dp)
>  			intel_wait_ddi_buf_idle(dev_priv, port);
>  	}
>  
> -	dp_tp_ctl = DP_TP_CTL_ENABLE |
> -		    DP_TP_CTL_LINK_TRAIN_PAT1 | DP_TP_CTL_SCRAMBLE_DISABLE;
> +	dp_tp_ctl = DP_TP_CTL_ENABLE | DP_TP_CTL_LINK_TRAIN_PAT1;
>  	if (intel_dp->link_mst)
>  		dp_tp_ctl |= DP_TP_CTL_MODE_MST;
>  	else {
> @@ -4066,11 +4065,6 @@ static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
>  
>  	temp = intel_de_read(dev_priv, intel_dp->regs.dp_tp_ctl);
>  
> -	if (dp_train_pat & DP_LINK_SCRAMBLING_DISABLE)
> -		temp |= DP_TP_CTL_SCRAMBLE_DISABLE;
> -	else
> -		temp &= ~DP_TP_CTL_SCRAMBLE_DISABLE;
> -
>  	temp &= ~DP_TP_CTL_LINK_TRAIN_MASK;
>  	switch (dp_train_pat & train_pat_mask) {
>  	case DP_TRAINING_PATTERN_DISABLE:
> -- 
> 2.23.1
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
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-- 
Ville Syrjälä
Intel
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