[PATCH v4 06/30] drm/dp_mst: Allow DSC in any Synaptics last branch device

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Mon, 2023-10-30 at 17:58 +0200, Imre Deak wrote:
> The Synaptics MST branch devices support DSC decompression on all their
> output ports, provided that they are last branch devices (with their
> output ports connected to the sinks). The Thinkpad 40B0 TBT dock for
> instance has two such branch devices, a secondary one connected to one
> of the output ports of the primary; hence the decompression needs to be
> enabled in both branch devices to enable decompression for all the
> sinks.
> 
> Based on the above add support for enabling decompression in last
> Synaptics branch devices.
> 
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: dri-devel at lists.freedesktop.org
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 21 ++++++++++++-------
>  1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index 5972c93615f18..cc0a8fe84d290 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -5994,6 +5994,7 @@ static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
>  struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
>  {
>  	struct drm_dp_mst_port *immediate_upstream_port;
> +	struct drm_dp_aux *immediate_upstream_aux;
>  	struct drm_dp_mst_port *fec_port;
>  	struct drm_dp_desc desc = {};
>  	u8 endpoint_fec;
> @@ -6058,21 +6059,25 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
>  	 * - Port is on primary branch device
>  	 * - Not a VGA adapter (DP_DWN_STRM_PORT_TYPE_ANALOG)
>  	 */
> -	if (drm_dp_read_desc(port->mgr->aux, &desc, true))
> +	if (immediate_upstream_port)
> +		immediate_upstream_aux = &immediate_upstream_port->aux;
> +	else
> +		immediate_upstream_aux = port->mgr->aux;
> +
> +	if (drm_dp_read_desc(immediate_upstream_aux, &desc, true))
>  		return NULL;
>  
> -	if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) &&
> -	    port->mgr->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
> -	    port->parent == port->mgr->mst_primary) {
> +	if (drm_dp_has_quirk(&desc, DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD)) {
>  		u8 dpcd_ext[DP_RECEIVER_CAP_SIZE];
>  
> -		if (drm_dp_read_dpcd_caps(port->mgr->aux, dpcd_ext) < 0)
> +		if (drm_dp_read_dpcd_caps(immediate_upstream_aux, dpcd_ext) < 0)
>  			return NULL;
>  
> -		if ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT) &&
> +		if (dpcd_ext[DP_DPCD_REV] >= DP_DPCD_REV_14 &&
> +		    ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT) &&
>  		    ((dpcd_ext[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_TYPE_MASK)
> -		     != DP_DWN_STRM_PORT_TYPE_ANALOG))
> -			return port->mgr->aux;
> +		     != DP_DWN_STRM_PORT_TYPE_ANALOG)))
> +			return immediate_upstream_aux;
>  	}
>  
>  	/*

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat