[Intel-gfx] [PATCH] drm/i915: Preserve the DDI_A_4_LANES bit from the bios

[Jesse Barnes]

On Fri, 12 Jul 2013 13:03:46 -0700
Stéphane Marchesin <marcheu at chromium.org> wrote:

> Otherwise the DDI_A_4_LANES bit gets lost and we can't use > 2 lanes
> on eDP. This fixes eDP on hsw with > 2 lanes.
> 
> Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 2 +-
>  drivers/gpu/drm/i915/intel_dp.c  | 5 +++--
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 324211a..5e3f97b 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -1348,7 +1348,7 @@ void intel_ddi_init(struct drm_device *dev, enum port port)
>  
>  	intel_dig_port->port = port;
>  	intel_dig_port->port_reversal = I915_READ(DDI_BUF_CTL(port)) &
> -					DDI_BUF_PORT_REVERSAL;
> +					(DDI_BUF_PORT_REVERSAL | DDI_A_4_LANES);
>  	intel_dig_port->dp.output_reg = DDI_BUF_CTL(port);
>  
>  	intel_encoder->type = INTEL_OUTPUT_UNKNOWN;
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index b739712..a1d838c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -834,10 +834,11 @@ intel_dp_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
>  	 * configuration happens (oddly) in ironlake_pch_enable
>  	 */
>  
> -	/* Preserve the BIOS-computed detected bit. This is
> +	/* Preserve the BIOS-computed detected and 4 lanes bits. This is
>  	 * supposed to be read-only.
>  	 */
> -	intel_dp->DP = I915_READ(intel_dp->output_reg) & DP_DETECTED;
> +	intel_dp->DP = I915_READ(intel_dp->output_reg) &
> +		       (DP_DETECTED | DDI_A_4_LANES);
>  
>  	/* Handle DP bits in common between all three register formats */
>  	intel_dp->DP |= DP_VOLTAGE_0_4 | DP_PRE_EMPHASIS_0;

Thanks.  Wonder if we're clobbering any other "BIOS must set this bit
and no one should touch it again" bits elsewhere...

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center