[Intel-gfx] [PATCH] drm/i915/cnl: Wa to ignore VBT alternate pin on B-stepping.

[Ville Syrjälä]

On Thu, Apr 06, 2017 at 05:54:26PM -0700, Rodrigo Vivi wrote:
> Current VBT available for pre-production machines
> tells that we need to use alternate pin. But if we use it
> we end up needing to define a different table.
> 
> However if we respect the spec, ignore the VBT for now
> we get a more reliable HDMI.
> 
> Cc: Clint Taylor <clinton.a.taylor at intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_hdmi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index f8c40ae..0d389bc 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1884,7 +1884,8 @@ static u8 intel_hdmi_ddc_pin(struct drm_i915_private *dev_priv,
>  		&dev_priv->vbt.ddi_port_info[port];
>  	u8 ddc_pin;
>  
> -	if (info->alternate_ddc_pin) {
> +	if (info->alternate_ddc_pin &&
> +	    !IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0)) {

So it's got broken VBT? In that case it would make more sense to me
to put the kludge into the VBT parsing code.

>  		DRM_DEBUG_KMS("Using DDC pin 0x%x for port %c (VBT)\n",
>  			      info->alternate_ddc_pin, port_name(port));
>  		return info->alternate_ddc_pin;
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC