Re: [PATCH v3 3/7] drm/i915: protect access to DP_TP_* on non-dp

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Aug 29, 2019 at 02:25:50AM -0700, Lucas De Marchi wrote:
> DP_TP_{CTL,STATUS} should only be programmed when the encoder is intel_dp.
> Checking its current usages intel_disable_ddi_buf() is the only
> offender, with other places being protected by checks like
> pipe_config->fec_enable that is only set by intel_dp.
> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 3180dacb5be4..df3e4fe7e3e9 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3462,10 +3462,12 @@ static void intel_disable_ddi_buf(struct intel_encoder *encoder,
>  		wait = true;
>  	}
>  
> -	val = I915_READ(DP_TP_CTL(port));
> -	val &= ~(DP_TP_CTL_ENABLE | DP_TP_CTL_LINK_TRAIN_MASK);
> -	val |= DP_TP_CTL_LINK_TRAIN_PAT1;
> -	I915_WRITE(DP_TP_CTL(port), val);
> +	if (intel_encoder_is_dp(encoder)) {

Doesn't really make sense to me. Either we just do it (because a DDI is
just a DDI so DP_TP_CTL does exist always), or we only do it when driving
DP and not when driving HDMI.

For the latter I would perhaps suggest moving all this extra junk out
from intel_disable_ddi_buf() into the DP specific code paths, leaving
just the actual DDI_BUF_CTL disable here.

> +		val = I915_READ(DP_TP_CTL(port));
> +		val &= ~(DP_TP_CTL_ENABLE | DP_TP_CTL_LINK_TRAIN_MASK);
> +		val |= DP_TP_CTL_LINK_TRAIN_PAT1;
> +		I915_WRITE(DP_TP_CTL(port), val);
> +	}
>  
>  	/* Disable FEC in DP Sink */
>  	intel_ddi_disable_fec_state(encoder, crtc_state);
> -- 
> 2.23.0

-- 
Ville Syrjälä
Intel
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