[PATCH v4 18/39] drm/msm/dp: add support to send ACT packets for MST

Yongxing Mou
2026-04-10T09:35:27Z

From: Abhinav Kumar <quic_abhinavk@quicinc.com>

Whenever virtual channel slot allocation changes, the DP
source must send the action control trigger sequence to notify
the sink about the same. This would be applicable during the
start and stop of the pixel stream. Add the infrastructure
to be able to send ACT packets for the DP controller when
operating in MST mode.

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_ctrl.c | 43 +++++++++++++++++++++++++++++++++++--
drivers/gpu/drm/msm/dp/dp_ctrl.h | 3 ++-
drivers/gpu/drm/msm/dp/dp_display.c | 3 ++-
drivers/gpu/drm/msm/dp/dp_display.h | 1 +
drivers/gpu/drm/msm/dp/dp_reg.h | 2 ++
5 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index 1109b2df21be..6f25145ef214 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -143,6 +143,7 @@ struct msm_dp_ctrl_private {
bool core_clks_on;
bool link_clks_on;
bool stream_clks_on[DP_STREAM_MAX];
+ bool mst_active;
};

static inline u32 msm_dp_read_ahb(const struct msm_dp_ctrl_private *ctrl, u32 offset)
@@ -228,6 +229,32 @@ static int msm_dp_aux_link_configure(struct drm_dp_aux *aux,
return err;
}

+int msm_dp_ctrl_mst_send_act(struct msm_dp_ctrl *msm_dp_ctrl)
+{
+ struct msm_dp_ctrl_private *ctrl;
+ bool act_complete;
+
+ ctrl = container_of(msm_dp_ctrl, struct msm_dp_ctrl_private, msm_dp_ctrl);
+
+ if (!ctrl->mst_active)
+ return 0;
+
+ msm_dp_write_link(ctrl, 0, REG_DP_MST_ACT, 0x1);
+ /* make sure ACT signal is performed */
+ wmb();
+
+ msleep(20); /* needs 1 frame time */
+
+ act_complete = msm_dp_read_link(ctrl, 0, REG_DP_MST_ACT);
+
+ if (!act_complete) {
+ drm_dbg_dp(ctrl->drm_dev, "MST ACT trigger complete failed\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
/*
* NOTE: resetting DP controller will also clear any pending HPD related interrupts
*/
@@ -2081,6 +2108,10 @@ static int msm_dp_ctrl_link_maintenance(struct msm_dp_ctrl_private *ctrl)

msm_dp_write_link(ctrl, 0, REG_DP_STATE_CTRL, DP_STATE_CTRL_SEND_VIDEO);

+ ret = msm_dp_ctrl_mst_send_act(&ctrl->msm_dp_ctrl);
+ if (ret)
+ return ret;
+
ret = msm_dp_ctrl_wait4video_ready(ctrl);
end:
return ret;
@@ -2277,7 +2308,7 @@ static int msm_dp_ctrl_process_phy_test_request(struct msm_dp_ctrl_private *ctrl
msm_dp_ctrl_off_pixel_clk(&ctrl->msm_dp_ctrl, ctrl->panel->stream_id);
msm_dp_ctrl_off_link(&ctrl->msm_dp_ctrl);

- ret = msm_dp_ctrl_on_link(&ctrl->msm_dp_ctrl);
+ ret = msm_dp_ctrl_on_link(&ctrl->msm_dp_ctrl, false);
if (ret) {
DRM_ERROR("failed to enable DP link controller\n");
return ret;
@@ -2357,7 +2388,7 @@ static bool msm_dp_ctrl_channel_eq_ok(struct msm_dp_ctrl_private *ctrl)
return drm_dp_channel_eq_ok(link_status, num_lanes);
}

-int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl)
+int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl, bool mst_active)
{
int rc = 0;
struct msm_dp_ctrl_private *ctrl;
@@ -2375,6 +2406,7 @@ int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl)

rate = ctrl->panel->link_info.rate;
pixel_rate = ctrl->panel->msm_dp_mode.drm_mode.clock;
+ ctrl->mst_active = mst_active;

msm_dp_ctrl_core_clk_enable(&ctrl->msm_dp_ctrl);

@@ -2654,6 +2686,10 @@ int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *

msm_dp_write_link(ctrl, 0, REG_DP_STATE_CTRL, DP_STATE_CTRL_SEND_VIDEO);

+ ret = msm_dp_ctrl_mst_send_act(msm_dp_ctrl);
+ if (ret)
+ return ret;
+
ret = msm_dp_ctrl_wait4video_ready(ctrl);
if (ret)
return ret;
@@ -2693,6 +2729,8 @@ void msm_dp_ctrl_off_link(struct msm_dp_ctrl *msm_dp_ctrl)

msm_dp_ctrl_reset(&ctrl->msm_dp_ctrl);

+ ctrl->mst_active = false;
+
dev_pm_opp_set_rate(ctrl->dev, 0);
msm_dp_ctrl_link_clk_disable(&ctrl->msm_dp_ctrl);

@@ -2876,6 +2914,7 @@ struct msm_dp_ctrl *msm_dp_ctrl_get(struct device *dev, struct msm_dp_link *link
ctrl->link_base = link_base;
ctrl->mst2link_base = mst2link_base;
ctrl->mst3link_base = mst3link_base;
+ ctrl->mst_active = false;

ret = msm_dp_ctrl_clk_init(&ctrl->msm_dp_ctrl, max_stream);
if (ret) {
diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.h b/drivers/gpu/drm/msm/dp/dp_ctrl.h
index e72d501ac1ce..f82fd96e412a 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.h
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.h
@@ -16,7 +16,7 @@ struct msm_dp_ctrl {

struct phy;

-int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl);
+int msm_dp_ctrl_on_link(struct msm_dp_ctrl *msm_dp_ctrl, bool mst_active);
int msm_dp_ctrl_on_stream(struct msm_dp_ctrl *msm_dp_ctrl, struct msm_dp_panel *msm_dp_panel);
int msm_dp_ctrl_prepare_stream_on(struct msm_dp_ctrl *msm_dp_ctrl, bool force_link_train);
void msm_dp_ctrl_off_link(struct msm_dp_ctrl *msm_dp_ctrl);
@@ -51,4 +51,5 @@ void msm_dp_ctrl_disable_irq(struct msm_dp_ctrl *msm_dp_ctrl);

void msm_dp_ctrl_reinit_phy(struct msm_dp_ctrl *msm_dp_ctrl);
int msm_dp_ctrl_get_stream_cnt(struct msm_dp_ctrl *dp_ctrl);
+int msm_dp_ctrl_mst_send_act(struct msm_dp_ctrl *msm_dp_ctrl);
#endif /* _DP_CTRL_H_ */
diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index a924fbd825f7..80bb5fc4003f 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -660,7 +660,7 @@ static int msm_dp_display_prepare(struct msm_dp_display_private *dp)
force_link_train = true;
}

- rc = msm_dp_ctrl_on_link(dp->ctrl);
+ rc = msm_dp_ctrl_on_link(dp->ctrl, msm_dp_display->mst_active);
if (rc)
DRM_ERROR("Failed link training (rc=%d)\n", rc);
// TODO: schedule drm_connector_set_link_status_property()
@@ -1547,6 +1547,7 @@ void msm_dp_display_atomic_disable(struct msm_dp *dp)
msm_dp_display = container_of(dp, struct msm_dp_display_private, msm_dp_display);

msm_dp_ctrl_push_idle(msm_dp_display->ctrl);
+ msm_dp_ctrl_mst_send_act(msm_dp_display->ctrl);
}

static void msm_dp_display_unprepare(struct msm_dp_display_private *dp)
diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
index b0cfdf215970..fdbe6e4871d9 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.h
+++ b/drivers/gpu/drm/msm/dp/dp_display.h
@@ -19,6 +19,7 @@ struct msm_dp {
struct drm_bridge *bridge;
bool audio_enabled;
bool power_on;
+ bool mst_active;
unsigned int connector_type;
bool is_edp;

diff --git a/drivers/gpu/drm/msm/dp/dp_reg.h b/drivers/gpu/drm/msm/dp/dp_reg.h
index 1c2d3d8d029d..237325d52dbd 100644
--- a/drivers/gpu/drm/msm/dp/dp_reg.h
+++ b/drivers/gpu/drm/msm/dp/dp_reg.h
@@ -156,6 +156,8 @@
#define DP_CONFIGURATION_CTRL_BPC_SHIFT (0x08)
#define DP_CONFIGURATION_CTRL_LSCLK_DIV_SHIFT (0x0D)

+#define REG_DP_MST_ACT (0x00000500)
+
#define REG_DP_SOFTWARE_MVID (0x00000010)
#define REG_DP_SOFTWARE_NVID (0x00000018)
#define REG_DP_TOTAL_HOR_VER (0x0000001C)

--
2.43.0