Re: [PATCH] drm/i915/cnl: DDIA Lane capability bit not set in clone mode

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

On Mon, Oct 16, 2017 at 04:44:49PM -0700, Rodrigo Vivi wrote:
> From: Clint Taylor <clinton.a.taylor@intel.com>
> 
> DDIA Lane capability control 4 lane bit is not being set by firmware during
> clone mode boot. This occurs when multiple monitors are connected during
> boot. The driver will configure the port for 2 lane maximum width if this
> bit is not set.
> 
> Cc: Mika Kahola <mika.kahola@intel.com>
> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index a9c0c16e3838..0ad915d71132 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2791,9 +2791,10 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
>  	 * configuration so that we use the proper lane count for our
>  	 * calculations.
>  	 */
> -	if (IS_GEN9_LP(dev_priv) && port == PORT_A) {
> +	if ((IS_GEN9_LP(dev_priv) || IS_CANNONLAKE(dev_priv)) &&
> +	    port == PORT_A) {
>  		if (!(intel_dig_port->saved_port_bits & DDI_A_4_LANES)) {
> -			DRM_DEBUG_KMS("BXT BIOS forgot to set DDI_A_4_LANES for port A; fixing\n");
> +			DRM_DEBUG_KMS("BIOS forgot to set DDI_A_4_LANES for port A\n");
>  			intel_dig_port->saved_port_bits |= DDI_A_4_LANES;
>  			max_lanes = 4;
>  		}

CNL has DDI E so this doesn't make sense. If there are CNLs out there
that don't actually use DDI E but forget to configure the bifurcation
coreectly, then we'll need a fancier way to detect that. Ie. we need to
be sure DDI E isn't going to be used before we can force DDI A to use
4 lanes.

-- 
Ville Syrjälä
Intel OTC
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