[PATCH 09/15] drm/dp_mst: Add new quirk for Synaptics MST hubs

[Lyude Paul]

Great work!

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

On Wed, 2019-09-18 at 16:26 -0400, mikita.lipski at amd.com wrote:
> From: David Francis <David.Francis at amd.com>
> 
> Synaptics DP1.4 hubs (BRANCH_ID 0x90CC24) do not
> support virtual DPCD registers, but do support DSC.
> The DSC caps can be read from the physical aux,
> like in SST DSC. These hubs have many different
> DEVICE_IDs.  Add a new quirk to detect this case.
> 
> Change-Id: I9d332f273dfca0cfbced111e62f5a06c5c312893
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Reviewed-by: Wenjing Liu <Wenjing.Liu at amd.com>
> Signed-off-by: David Francis <David.Francis at amd.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c       |  4 +++-
>  drivers/gpu/drm/drm_dp_mst_topology.c | 27 +++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h           |  7 +++++++
>  3 files changed, 37 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c
> b/drivers/gpu/drm/drm_dp_helper.c
> index 0cbf10727bd6..c3e1da78e442 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -1288,7 +1288,9 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
>  	/* LG LP140WF6-SPM1 eDP panel */
>  	{ OUI(0x00, 0x22, 0xb9), DEVICE_ID('s', 'i', 'v', 'a', 'r', 'T'),
> false, BIT(DP_DPCD_QUIRK_CONSTANT_N) },
>  	/* Apple panels need some additional handling to support PSR */
> -	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false,
> BIT(DP_DPCD_QUIRK_NO_PSR) }
> +	{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false,
> BIT(DP_DPCD_QUIRK_NO_PSR) },
> +	/* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */
> +	{ OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true,
> BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) },
>  };
>  
>  #undef OUI
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index dd2ca065cc92..4e493d8af288 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -4219,6 +4219,7 @@ 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_mst_port *fec_port;
> +	struct drm_dp_desc desc = { 0 };
>  
>  	if (!port)
>  		return NULL;
> @@ -4271,6 +4272,32 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct
> drm_dp_mst_port *port)
>  	if (drm_dp_mst_is_virtual_dpcd(port))
>  		return &port->aux;
>  
> +	/*
> +	 * Synaptics quirk
> +	 * Applies to ports for which:
> +	 * - Physical aux has Synaptics OUI
> +	 * - DPv1.4 or higher
> +	 * - 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))
> +		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) {
> +		u8 downstreamport;
> +
> +		if (drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
> +				     &downstreamport, 1) < 0)
> +			return NULL;
> +
> +		if ((downstreamport & DP_DWN_STRM_PORT_PRESENT) &&
> +		   ((downstreamport & DP_DWN_STRM_PORT_TYPE_MASK)
> +		     != DP_DWN_STRM_PORT_TYPE_ANALOG))
> +			return port->mgr->aux;
> +	}
> +
>  	return NULL;
>  }
>  EXPORT_SYMBOL(drm_dp_mst_dsc_aux_for_port);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 6ae1a6765f63..919ad940bfb1 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1414,6 +1414,13 @@ enum drm_dp_quirk {
>  	 * driver still need to implement proper handling for such device.
>  	 */
>  	DP_DPCD_QUIRK_NO_PSR,
> +	/**
> +	 * @DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD:
> +	 *
> +	 * The device supports MST DSC despite not supporting Virtual DPCD.
> +	 * The DSC caps can be read from the physical aux instead.
> +	 */
> +	DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD,
>  };
>  
>  /**
-- 
Cheers,
	Lyude Paul