[PATCH v4 36/39] drm/msm/dp: add connector abstraction for DP MST

Yongxing Mou
2026-04-10T09:36:55Z

From: Abhinav Kumar <quic_abhinavk@quicinc.com>

Introduce an MST connector abstraction for DP MST, with each MST
connector associated with a DP panel and connected through a DRM bridge
to an MST encoder.

The connector is only used for MST helper callbacks, such as detect,
get_modes, and get_encoder. Display enable/disable, hotplug handling,
and modeset sequencing continue to be handled by the bridge path.

Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
---
drivers/gpu/drm/msm/dp/dp_mst_drm.c | 231 ++++++++++++++++++++++++++++++++++++
1 file changed, 231 insertions(+)

diff --git a/drivers/gpu/drm/msm/dp/dp_mst_drm.c b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
index 4df3ea5e36d0..bb3898b1f6b1 100644
--- a/drivers/gpu/drm/msm/dp/dp_mst_drm.c
+++ b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
@@ -7,6 +7,7 @@
#include <drm/drm_managed.h>
#include <drm/drm_bridge.h>
#include <drm/display/drm_dp_mst_helper.h>
+#include <linux/pm_runtime.h>

#include "dp_mst_drm.h"
#include "dp_panel.h"
@@ -489,6 +490,235 @@ int msm_dp_mst_display_set_mgr_state(struct msm_dp *dp_display, bool state)
return rc;
}

+/* DP MST Connector OPs */
+static int
+msm_dp_mst_connector_detect(struct drm_connector *connector,
+ struct drm_modeset_acquire_ctx *ctx,
+ bool force)
+{
+ struct msm_dp_mst_connector *mst_conn = to_dp_mst_connector(connector);
+ struct msm_dp_mst *mst = mst_conn->dp_mst;
+ struct msm_dp *dp_display = mst->msm_dp;
+ struct device *dev = dp_display->drm_dev->dev;
+ enum drm_connector_status status = connector_status_disconnected;
+ int ret;
+
+ ret = pm_runtime_resume_and_get(dev);
+ if (ret < 0)
+ return status;
+
+ if (dp_display->mst_active)
+ status = drm_dp_mst_detect_port(connector,
+ ctx, &mst->mst_mgr, mst_conn->mst_port);
+
+ pm_runtime_put_autosuspend(dev);
+
+ return status;
+}
+
+static int msm_dp_mst_connector_get_modes(struct drm_connector *connector)
+{
+ struct msm_dp_mst_connector *mst_conn = to_dp_mst_connector(connector);
+ struct msm_dp_mst *mst = mst_conn->dp_mst;
+ const struct drm_edid *drm_edid;
+
+ drm_edid = drm_dp_mst_edid_read(connector, &mst->mst_mgr, mst_conn->mst_port);
+ drm_edid_connector_update(connector, drm_edid);
+
+ return drm_edid_connector_add_modes(connector);
+}
+
+static enum drm_mode_status msm_dp_mst_connector_mode_valid(struct drm_connector *connector,
+ const struct drm_display_mode *mode)
+{
+ struct msm_dp_mst_connector *mst_conn;
+ struct drm_dp_mst_port *mst_port;
+ struct msm_dp *dp_display;
+ int required_pbn;
+
+ if (drm_connector_is_unregistered(connector))
+ return 0;
+
+ mst_conn = to_dp_mst_connector(connector);
+ mst_port = mst_conn->mst_port;
+ dp_display = mst_conn->dp_mst->msm_dp;
+
+ if (!mst_port)
+ return MODE_ERROR;
+
+ required_pbn = drm_dp_calc_pbn_mode(mode->clock, (6 * 3) << 4);
+
+ if (required_pbn > mst_port->full_pbn) {
+ drm_dbg_dp(dp_display->drm_dev, "mode:%s not supported.\n", mode->name);
+ return MODE_CLOCK_HIGH;
+ }
+
+ return msm_dp_display_mode_valid(dp_display, &connector->display_info, mode);
+}
+
+static struct drm_encoder *
+msm_dp_mst_atomic_best_encoder(struct drm_connector *connector, struct drm_atomic_state *state)
+{
+ struct msm_dp_mst_connector *mst_conn = to_dp_mst_connector(connector);
+ struct msm_dp_mst *mst = mst_conn->dp_mst;
+ struct msm_dp *dp_display = mst->msm_dp;
+ struct drm_encoder *enc = NULL;
+ struct msm_dp_mst_bridge_state *mst_bridge_state;
+ u32 i;
+ struct drm_connector_state *conn_state = drm_atomic_get_new_connector_state(state,
+ connector);
+
+ if (conn_state && conn_state->best_encoder)
+ return conn_state->best_encoder;
+
+ for (i = 0; i < mst->max_streams; i++) {
+ mst_bridge_state = msm_dp_mst_br_priv_state(state, mst->mst_bridge[i]);
+ if (IS_ERR(mst_bridge_state))
+ goto end;
+
+ if (mst_bridge_state->connector == connector) {
+ enc = mst->mst_bridge[i]->encoder;
+ goto end;
+ }
+ }
+
+ for (i = 0; i < mst->max_streams; i++) {
+ mst_bridge_state = msm_dp_mst_br_priv_state(state, mst->mst_bridge[i]);
+
+ if (!mst_bridge_state->connector) {
+ mst_bridge_state->connector = connector;
+ mst_bridge_state->msm_dp_panel = mst_conn->dp_panel;
+ enc = mst->mst_bridge[i]->encoder;
+ break;
+ }
+ }
+
+end:
+ if (enc)
+ drm_dbg_dp(dp_display->drm_dev, "MST connector:%d atomic best encoder:%d\n",
+ connector->base.id, i);
+ else
+ drm_dbg_dp(dp_display->drm_dev, "MST connector:%d atomic best encoder failed\n",
+ connector->base.id);
+
+ return enc;
+}
+
+static int msm_dp_mst_connector_atomic_check(struct drm_connector *connector,
+ struct drm_atomic_state *state)
+{
+ struct msm_dp_mst_connector *mst_conn = to_dp_mst_connector(connector);
+ struct msm_dp_mst *mst = mst_conn->dp_mst;
+
+ return drm_dp_atomic_release_time_slots(state, &mst->mst_mgr, mst_conn->mst_port);
+}
+
+static void dp_mst_connector_destroy(struct drm_connector *connector)
+{
+ struct msm_dp_mst_connector *mst_conn = to_dp_mst_connector(connector);
+
+ drm_connector_cleanup(connector);
+ drm_dp_mst_put_port_malloc(mst_conn->mst_port);
+ kfree(mst_conn);
+}
+
+/* DRM MST callbacks */
+static const struct drm_connector_helper_funcs msm_dp_drm_mst_connector_helper_funcs = {
+ .get_modes = msm_dp_mst_connector_get_modes,
+ .detect_ctx = msm_dp_mst_connector_detect,
+ .mode_valid = msm_dp_mst_connector_mode_valid,
+ .atomic_best_encoder = msm_dp_mst_atomic_best_encoder,
+ .atomic_check = msm_dp_mst_connector_atomic_check,
+};
+
+static const struct drm_connector_funcs msm_dp_drm_mst_connector_funcs = {
+ .reset = drm_atomic_helper_connector_reset,
+ .destroy = dp_mst_connector_destroy,
+ .fill_modes = drm_helper_probe_single_connector_modes,
+ .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+ .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static struct drm_connector *
+msm_dp_mst_add_connector(struct drm_dp_mst_topology_mgr *mgr,
+ struct drm_dp_mst_port *port, const char *pathprop)
+{
+ struct msm_dp_mst *dp_mst;
+ struct drm_device *dev;
+ struct msm_dp *dp_display;
+ struct msm_dp_mst_connector *mst_conn;
+ struct drm_connector *connector;
+ int rc, i;
+
+ dp_mst = container_of(mgr, struct msm_dp_mst, mst_mgr);
+
+ dp_display = dp_mst->msm_dp;
+ dev = dp_display->drm_dev;
+
+ mst_conn = kzalloc_obj(*mst_conn);
+
+ if (!mst_conn)
+ return NULL;
+
+ drm_modeset_lock_all(dev);
+
+ connector = &mst_conn->connector;
+ rc = drm_connector_dynamic_init(dev, connector,
+ &msm_dp_drm_mst_connector_funcs,
+ DRM_MODE_CONNECTOR_DisplayPort, NULL);
+ if (rc) {
+ kfree(mst_conn);
+ drm_modeset_unlock_all(dev);
+ return NULL;
+ }
+
+ mst_conn->dp_panel = msm_dp_display_get_panel(dp_display);
+ if (!mst_conn->dp_panel) {
+ DRM_ERROR("failed to get dp_panel for connector\n");
+ kfree(mst_conn);
+ drm_modeset_unlock_all(dev);
+ return NULL;
+ }
+
+ mst_conn->dp_panel->connector = connector;
+ mst_conn->dp_mst = dp_mst;
+
+ drm_connector_helper_add(connector, &msm_dp_drm_mst_connector_helper_funcs);
+
+ if (connector->funcs->reset)
+ connector->funcs->reset(connector);
+
+ /* add all encoders as possible encoders */
+ for (i = 0; i < dp_mst->max_streams; i++) {
+ rc = drm_connector_attach_encoder(connector, dp_mst->mst_bridge[i]->encoder);
+
+ if (rc) {
+ DRM_ERROR("failed to attach encoder to connector, %d\n", rc);
+ kfree(mst_conn);
+ drm_modeset_unlock_all(dev);
+ return NULL;
+ }
+ }
+
+ mst_conn->mst_port = port;
+ drm_dp_mst_get_port_malloc(mst_conn->mst_port);
+
+ drm_object_attach_property(&connector->base,
+ dev->mode_config.path_property, 0);
+ drm_object_attach_property(&connector->base,
+ dev->mode_config.tile_property, 0);
+ drm_connector_set_path_property(connector, pathprop);
+ drm_modeset_unlock_all(dev);
+
+ drm_dbg_dp(dp_display->drm_dev, "add MST connector id:%d\n", connector->base.id);
+
+ return connector;
+}
+
+static const struct drm_dp_mst_topology_cbs msm_dp_mst_drm_cbs = {
+ .add_connector = msm_dp_mst_add_connector,
+};
+
int msm_dp_mst_init(struct msm_dp *dp_display, u32 max_streams, struct drm_dp_aux *drm_aux)
{
struct drm_device *dev = dp_display->drm_dev;
@@ -501,6 +731,7 @@ int msm_dp_mst_init(struct msm_dp *dp_display, u32 max_streams, struct drm_dp_au
return -ENOMEM;

memset(&msm_dp_mst->mst_mgr, 0, sizeof(msm_dp_mst->mst_mgr));
+ msm_dp_mst->mst_mgr.cbs = &msm_dp_mst_drm_cbs;
conn_base_id = dp_display->connector->base.id;
msm_dp_mst->msm_dp = dp_display;
msm_dp_mst->max_streams = max_streams;

--
2.43.0