[Intel-gfx] [PATCH v2 4/4] drm/i915/icl: Add fallback detection method for TypeC legacy ports

[Kahola, Mika]

The v2 looks ok to me.

On Fri, 2018-12-14 at 20:27 +0200, Imre Deak wrote:
> Add a fallback detection method for TypeC legacy ports in case the
> VBT port information used to detect normally such ports is
> incorrect.
> 
> For the fallback method we use the TypeC legacy mode specific HPD
> interrupt flag which should only be raised for a legacy port.
> 
> WARN if the VBT port info is incorrect.
> 
> In a case where we'd detect the port in a contradicting way both as a
> legacy and also as a USB DP and/or TBT alternate port treat the port
> as legacy (by also emitting a WARN from icl_update_tc_port_type).
> 
> v2:
> - Repurpose the detection as a fallback method instead of using
>   it only for the DP legacy case. By now we should normally use VBT
> to
>   detect DP legacy ports as well.
> 
> Suggested-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: José Roberto de Souza <jose.souza at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com> (v1)
Reviewed-by: Mika Kahola <mika.kahola at intel.com> (v2)

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index b2a3012478ca..d00af92cd089 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5220,8 +5220,14 @@ static bool icl_tc_port_connected(struct
> drm_i915_private *dev_priv,
>  	bool is_legacy, is_typec, is_tbt;
>  	u32 dpsp;
>  
> -	is_legacy = intel_dig_port->tc_legacy_port ||
> -		I915_READ(SDEISR) & SDE_TC_HOTPLUG_ICP(tc_port);
> +	/*
> +	 * WARN if we got a legacy port HPD, but VBT didn't mark the
> port as
> +	 * legacy. Treat the port as legacy from now on.
> +	 */
> +	if (WARN_ON(!intel_dig_port->tc_legacy_port &&
> +		    I915_READ(SDEISR) & SDE_TC_HOTPLUG_ICP(tc_port)))
> +		intel_dig_port->tc_legacy_port = true;
> +	is_legacy = intel_dig_port->tc_legacy_port;
>  
>  	/*
>  	 * The spec says we shouldn't be using the ISR bits for
> detecting