Re: [PATCH 2/2] drm/i915/vbt: split out defaults that are set when there is no VBT

[Manasi Navare <manasi.d.navare@intel.com>]

On Fri, Mar 10, 2017 at 03:27:58PM +0200, Jani Nikula wrote:
> The main thing are the DDI ports. If there's a VBT that says there are
> no outputs, we should trust that, and not have semi-random
> defaults. Unfortunately, the defaults have resulted in some Chromebooks
> without VBT to rely on this behaviour, so we split out the defaults for
> the missing VBT case.
> 
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_bios.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 710988d72253..639d45c1dd2e 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1341,6 +1341,7 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
>  	return;
>  }
>  
> +/* Common defaults which may be overridden by VBT. */
>  static void
>  init_vbt_defaults(struct drm_i915_private *dev_priv)
>  {
> @@ -1377,6 +1378,18 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
>  			&dev_priv->vbt.ddi_port_info[port];
>  
>  		info->hdmi_level_shift = HDMI_LEVEL_SHIFT_UNKNOWN;
> +	}
> +}
> +
> +/* Defaults to initialize only if there is no VBT. */
> +static void
> +init_vbt_missing_defaults(struct drm_i915_private *dev_priv)
> +{
> +	enum port port;
> +
> +	for (port = PORT_A; port < I915_MAX_PORTS; port++) {
> +		struct ddi_vbt_port_info *info =
> +			&dev_priv->vbt.ddi_port_info[port];
>  
>  		info->supports_dvi = (port != PORT_A && port != PORT_E);
>  		info->supports_hdmi = info->supports_dvi;
> @@ -1516,8 +1529,10 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>  	parse_ddi_ports(dev_priv, bdb);
>  
>  out:
> -	if (!vbt)
> +	if (!vbt) {
>  		DRM_INFO("Failed to find VBIOS tables (VBT)\n");
> +		init_vbt_missing_defaults(dev_priv);
> +	}

So in case there is no VBT, this will set supports_DP flag on Port A.
What is there is no VBT and there is no eDP on Port A?
In this case it will still try to link train on Port A and fail..?
I am not sure if this case exists, but just a thought looking at it.
If such a case does not exist, then this will solve our problem of
current failures because leaving defaults on Port A. So in that case
it lgtm.

Regards
Manasi


>  
>  	if (bios)
>  		pci_unmap_rom(pdev, bios);
> -- 
> 2.1.4
> 
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