Add drm_dp_mst_dsc_aux_for_port. To enable DSC, the DSC_ENABLED
register might have to be written on the leaf port's DPCD,
its parent's DPCD, or the MST manager's DPCD. This function
finds the correct aux for the job.
As part of this, add drm_dp_mst_is_virtual_dpcd. Virtual DPCD
is a DP feature new in DP v1.4, which exposes certain DPCD
registers on virtual ports.
ALso add a new quirk for Synatics MST hubs that support DSC
despite not supporting virtual DPCD.
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: Wenjing Liu <Wenjing.Liu@xxxxxxx>
Cc: Nikola Cornij <Nikola.Cornij@xxxxxxx>
Signed-off-by: David Francis <David.Francis@xxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 2 +
drivers/gpu/drm/drm_dp_mst_topology.c | 147 ++++++++++++++++++++++++++
include/drm/drm_dp_helper.h | 7 ++
include/drm/drm_dp_mst_helper.h | 2 +
4 files changed, 158 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 2cc21eff4cf3..fc39323e7d52 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -1270,6 +1270,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = {
{ OUI(0x00, 0x10, 0xfa), DEVICE_ID_ANY, false, BIT(DP_DPCD_QUIRK_NO_PSR) },
/* CH7511 seems to leave SINK_COUNT zeroed */
{ OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) },
+ /* 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 a39e42c7d868..559bc09b6b94 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4150,3 +4150,150 @@ static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
{
i2c_del_adapter(&aux->ddc);
}
+
+/**
+ * drm_dp_mst_is_virtual_dpcd() - Is the given port a virtual DP Peer Device
+ * @port: The port to check
+ *
+ * A single physical MST hub object can be represented in the topology
+ * by multiple branches, with virtual ports between those branches.
+ *
+ * As of DP1.4, An MST hub with internal (virtual) ports must expose
+ * certain DPCD registers over those ports. See sections 2.6.1.1.1
+ * and 2.6.1.1.2 of Display Port specification v1.4 for details.
+ *
+ * May acquire mgr->lock
+ *
+ * Returns:
+ * true if the port is a virtual DP peer device, false otherwise
+ */
+static bool drm_dp_mst_is_virtual_dpcd(struct drm_dp_mst_port *port)
+{
+ struct drm_dp_mst_port *downstream_port;
+
+ if (!port)
+ return false;
+
+ /* Virtual DP Sink (Internal Display Panel) */
+ if (port->port_num >= 8 && port->dpcd_rev >= DP_DPCD_REV_14)
+ return true;
+
+ /* DP-to-HDMI Protocol Converter */
+ if (port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV &&
+ !port->mcs &&
+ port->ldps &&
+ port->dpcd_rev >= DP_DPCD_REV_14)
+ return true;
+
+ /* DP-to-DP */
+ mutex_lock(&port->mgr->lock);
+ if (port->pdt == DP_PEER_DEVICE_MST_BRANCHING &&
+ port->mstb &&
+ port->dpcd_rev >= DP_DPCD_REV_14 &&
+ port->mstb->num_ports == 2) {
+ list_for_each_entry(downstream_port, &port->mstb->ports, next) {
+ if (!downstream_port->input &&
+ downstream_port->pdt == DP_PEER_DEVICE_SST_SINK)
+ return true;
+ }
+ }
+ mutex_unlock(&port->mgr->lock);
+
+ return false;
+}
+
+/**
+ * drm_dp_mst_dsc_aux_for_port() - Find the correct aux for DSC
+ * @port: The port to check. A leaf of the MST tree with an attached display.
+ *
+ * Depending on the situation, DSC may be enabled via the endpoint aux,
+ * the immediately upstream aux, or the connector's physical aux.
+ *
+ * This is both the correct aux to read DSC_CAPABILITY and the
+ * correct aux to write DSC_ENABLED.
+ *
+ * This operation can be expensive (up to four aux reads), so
+ * the caller should cache the return.
+ *
+ * Returns:
+ * NULL if DSC cannot be enabled on this port, otherwise the aux device
+ */
+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;
+
+ if (port && port->parent)
+ immediate_upstream_port = port->parent->port_parent;
+ else
+ immediate_upstream_port = NULL;
+
+ fec_port = immediate_upstream_port;
+ while (fec_port) {
+ /*
+ * Each physical link (i.e. not a virtual port) between the
+ * output and the primary device must support FEC
+ */
+ if (!drm_dp_mst_is_virtual_dpcd(fec_port) &&
+ !fec_port->fec_capable)
+ return NULL;
+
+ fec_port = fec_port->parent->port_parent;
+ }
+
+ /* Enpoint decompression with DP-to-DP peer device */
+ if (drm_dp_mst_is_virtual_dpcd(immediate_upstream_port)) {
+ u8 upstream_dsc;
+ u8 endpoint_dsc;
+ u8 endpoint_fec;
+
+ if (drm_dp_dpcd_read(&port->aux,
+ DP_DSC_SUPPORT, &endpoint_dsc, 1) < 0)
+ return NULL;
+ if (drm_dp_dpcd_read(&port->aux,
+ DP_FEC_CAPABILITY, &endpoint_fec, 1) < 0)
+ return NULL;
+ if (drm_dp_dpcd_read(&immediate_upstream_port->aux,
+ DP_DSC_SUPPORT, &upstream_dsc, 1) < 0)
+ return NULL;
+
+ if ((endpoint_dsc & DP_DSC_DECOMPRESSION_IS_SUPPORTED)
+ && (endpoint_fec & DP_FEC_CAPABLE)
+ && (upstream_dsc & 0x2) /* DSC passthrough */)
+ return &port->aux;
+
+ /* Virtual DPCD decompression with DP-to-DP peer device */
+ return &immediate_upstream_port->aux;
+ }
+
+ /* Virtual DPCD decompression with DP-to-HDMI or Virtual DP Sink */
+ 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)
+ */
+ drm_dp_read_desc(port->mgr->aux, desc, true);
+ 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;
+
+ drm_dp_dpcd_read(&port->aux, DP_DOWNSTREAMPORT_PRESENT,
+ &downstreamport, 1);
+
+ 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 8364502f92cf..a1331b08705f 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1434,6 +1434,13 @@ enum drm_dp_quirk {
* The driver should ignore SINK_COUNT during detection.
*/
DP_DPCD_QUIRK_NO_SINK_COUNT,
+ /**
+ * @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,
};
/**
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index f113ae04fa88..4cf738545dfb 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -673,6 +673,8 @@ int __must_check drm_dp_mst_atomic_check(struct drm_atomic_state *state);
void drm_dp_mst_get_port_malloc(struct drm_dp_mst_port *port);
void drm_dp_mst_put_port_malloc(struct drm_dp_mst_port *port);
+struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port);
+
extern const struct drm_private_state_funcs drm_dp_mst_topology_state_funcs;
/**
--
2.17.1
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