[Intel-gfx] [PATCH] drm/i915/bxt: Force port A DDI to use 4 lanes

[Bob Paauwe]

On Thu, 5 Nov 2015 14:53:32 -0800
Matt Roper <matthew.d.roper at intel.com> wrote:

> The bspec indicates that DDI A using four lanes is the only valid
> configuration for Broxton (Broxton doesn't have a DDI E to split these
> lanes with); the DDI_A_4_LANES bit of port A's DDI_BUF_CTL should always
> be set by the BIOS.  However some BIOS versions seem to only be setting
> this bit if eDP is actually lit up at boot time; if the BIOS doesn't
> turn on the eDP panel because an external display is plugged in, then
> this bit is never properly initialized.  The end result of this is that
> we wind up calculating a lower max data rate than we should and may wind
> up rejecting the native mode for panels that we should be able to drive.
> 
> Let's workaround this BIOS bug by just turning the DDI_A_4_LANES bit on
> in our driver's internal state if we recognize that're running on BXT
> where it should have been on anyway.
> 
> Cc: Imre Deak <imre.deak at intel.com>
> Cc: Bob Paauwe <bob.j.paauwe at intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index b164122..672b86c 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -3234,6 +3234,19 @@ void intel_ddi_init(struct drm_device *dev, enum port port)
>  					  (DDI_BUF_PORT_REVERSAL |
>  					   DDI_A_4_LANES);
>  
> +	/*
> +	 * Bspec says that DDI_A_4_LANES is the only supported configuration
> +	 * for Broxton.  Yet some BIOS fail to set this bit on port A if eDP
> +	 * wasn't lit up at boot.  Force this bit on in our internal
> +	 * configuration so that we use the proper lane count for our
> +	 * calculations.
> +	 */
> +	if (IS_BROXTON(dev) && 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");
> +		intel_dig_port->saved_port_bits |= DDI_A_4_LANES;
> +	}

The brace isn't lined up with the proper if.

> +
>  	intel_encoder->type = INTEL_OUTPUT_UNKNOWN;
>  	intel_encoder->crtc_mask = (1 << 0) | (1 << 1) | (1 << 2);
>  	intel_encoder->cloneable = 0;

With the above formatting fixed.
Reviewed-by: Bob Paauwe <bob.j.paauwe at intel.com>
Tested-by: Bob Paauwe <bob.j.paauwe at intel.com>

-- 
--
Bob Paauwe                  
Bob.J.Paauwe at intel.com
IOTG / PED Software Organization
Intel Corp.  Folsom, CA
(916) 356-6193