Re: [PATCH v4 33/39] drm/msm/dp: initialize dp_mst module for each DP MST controller

[Dmitry Baryshkov]

On Fri, Apr 10, 2026 at 05:34:08PM +0800, Yongxing Mou wrote:
> From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> 
> For each MST capable DP controller, initialize a dp_mst module to
> manage its DP MST operations. The DP MST module for each controller
> is the central entity to manage its topology related operations as
> well as interfacing with the rest of the DP driver.
> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
> Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/Makefile            |  3 +-
>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c |  6 +++
>  drivers/gpu/drm/msm/dp/dp_display.c     | 18 ++++++++
>  drivers/gpu/drm/msm/dp/dp_display.h     |  2 +
>  drivers/gpu/drm/msm/dp/dp_mst_drm.c     | 73 +++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/dp/dp_mst_drm.h     | 13 ++++++
>  drivers/gpu/drm/msm/msm_drv.h           |  6 +++
>  7 files changed, 120 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
> index 8b94c5f1cb68..1d8426876aa1 100644
> --- a/drivers/gpu/drm/msm/Makefile
> +++ b/drivers/gpu/drm/msm/Makefile
> @@ -144,7 +144,8 @@ msm-display-$(CONFIG_DRM_MSM_DP)+= dp/dp_aux.o \
>  	dp/dp_link.o \
>  	dp/dp_panel.o \
>  	dp/dp_audio.o \
> -	dp/dp_utils.o
> +	dp/dp_utils.o \
> +	dp/dp_mst_drm.o
>  
>  msm-display-$(CONFIG_DRM_MSM_HDMI_HDCP) += hdmi/hdmi_hdcp.o
>  
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index 090e7d790593..d7ce13a4586d 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -680,6 +680,12 @@ static int _dpu_kms_initialize_displayport(struct drm_device *dev,
>  		stream_cnt = msm_dp_get_mst_max_stream(priv->kms->dp[i]);
>  
>  		if (stream_cnt > 1) {
> +			rc = msm_dp_mst_register(priv->kms->dp[i]);
> +			if (rc) {
> +				DPU_ERROR("dp_mst_init failed for DP, rc = %d\n", rc);
> +				return rc;
> +			}
> +
>  			for (stream_id = 0; stream_id < stream_cnt; stream_id++) {
>  				encoder = dpu_encoder_init(dev, DRM_MODE_ENCODER_DPMST, &info);
>  				if (IS_ERR(encoder)) {
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 9eaf6994a350..919767945ba5 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -28,6 +28,7 @@
>  #include "dp_drm.h"
>  #include "dp_audio.h"
>  #include "dp_debug.h"
> +#include "dp_mst_drm.h"
>  
>  static bool psr_enabled = false;
>  module_param(psr_enabled, bool, 0);
> @@ -360,6 +361,9 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>  	if (dp->max_stream > 1 && drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd))
>  		msm_dp_display_mst_init(dp);
>  
> +	if (dp->msm_dp_display.mst_active)
> +		msm_dp_mst_display_set_mgr_state(&dp->msm_dp_display, true);
> +
>  	msm_dp_link_reset_phy_params_vx_px(dp->link);
>  
>  end:
> @@ -527,6 +531,11 @@ static int msm_dp_hpd_unplug_handle(struct msm_dp_display_private *dp)
>  						 dp->panel->dpcd,
>  						 dp->panel->downstream_ports);
>  
> +	if (dp->msm_dp_display.mst_active) {
> +		msm_dp_mst_display_set_mgr_state(&dp->msm_dp_display, false);
> +		dp->msm_dp_display.mst_active = false;
> +	}
> +
>  	/* signal the disconnect event early to ensure proper teardown */
>  	msm_dp_display_handle_plugged_change(&dp->msm_dp_display, false);
>  
> @@ -1556,6 +1565,15 @@ int msm_dp_modeset_init(struct msm_dp *msm_dp_display, struct drm_device *dev,
>  	return 0;
>  }
>  
> +int msm_dp_mst_register(struct msm_dp *msm_dp_display)
> +{
> +	struct msm_dp_display_private *dp;
> +
> +	dp = container_of(msm_dp_display, struct msm_dp_display_private, msm_dp_display);
> +
> +	return msm_dp_mst_init(msm_dp_display, dp->max_stream, dp->aux);
> +}
> +
>  int msm_dp_display_set_mode_helper(struct msm_dp *msm_dp_display,
>  				   struct drm_atomic_state *state,
>  				   struct drm_encoder *drm_encoder,
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index bda76319c459..55874daf41c4 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -24,6 +24,8 @@ struct msm_dp {
>  	bool is_edp;
>  	bool prepared;
>  
> +	void *msm_dp_mst;
> +
>  	struct msm_dp_audio *msm_dp_audio;
>  	bool psr_supported;
>  };
> diff --git a/drivers/gpu/drm/msm/dp/dp_mst_drm.c b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
> new file mode 100644
> index 000000000000..b6c7b8211025
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/dp/dp_mst_drm.c
> @@ -0,0 +1,73 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2025 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <drm/drm_edid.h>
> +#include <drm/drm_managed.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/display/drm_dp_mst_helper.h>
> +
> +#include "dp_mst_drm.h"
> +#include "dp_panel.h"
> +
> +#define MAX_DPCD_TRANSACTION_BYTES 16
> +
> +struct msm_dp_mst {
> +	struct drm_dp_mst_topology_mgr mst_mgr;
> +	struct msm_dp *msm_dp;
> +	struct drm_dp_aux *dp_aux;
> +	u32 max_streams;
> +	/* Protects MST bridge enable/disable handling. */
> +	struct mutex mst_lock;

I don't see it being used here. Please drop. Isn't mst_mgr->lock enough?

> +};
> +
> +int msm_dp_mst_display_set_mgr_state(struct msm_dp *dp_display, bool state)
> +{
> +	struct msm_dp_mst *mst = dp_display->msm_dp_mst;
> +	int rc;
> +
> +	rc = drm_dp_mst_topology_mgr_set_mst(&mst->mst_mgr, state);
> +	if (rc < 0) {
> +		DRM_ERROR("failed to set topology mgr state to %d. rc %d\n",
> +			  state, rc);
> +	}
> +
> +	drm_dbg_dp(dp_display->drm_dev, "dp_mst_display_set_mgr_state state:%d\n", state);
> +	return rc;
> +}
> +
> +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;
> +	int conn_base_id = 0;
> +	int ret;
> +	struct msm_dp_mst *msm_dp_mst;
> +
> +	msm_dp_mst = devm_kzalloc(dev->dev, sizeof(*msm_dp_mst), GFP_KERNEL);
> +	if (!msm_dp_mst)
> +		return -ENOMEM;
> +
> +	memset(&msm_dp_mst->mst_mgr, 0, sizeof(msm_dp_mst->mst_mgr));
> +
> +	conn_base_id = dp_display->connector->base.id;
> +	msm_dp_mst->msm_dp = dp_display;
> +	msm_dp_mst->max_streams = max_streams;
> +
> +	msm_dp_mst->dp_aux = drm_aux;
> +
> +	ret = drm_dp_mst_topology_mgr_init(&msm_dp_mst->mst_mgr, dev,
> +					   drm_aux,
> +					   MAX_DPCD_TRANSACTION_BYTES,

Inline 16 here.

> +					   max_streams,
> +					   conn_base_id);
> +	if (ret) {
> +		DRM_ERROR("DP DRM MST topology manager init failed\n");
> +		return ret;
> +	}
> +
> +	dp_display->msm_dp_mst = msm_dp_mst;
> +
> +	mutex_init(&msm_dp_mst->mst_lock);
> +	return ret;
> +}
> diff --git a/drivers/gpu/drm/msm/dp/dp_mst_drm.h b/drivers/gpu/drm/msm/dp/dp_mst_drm.h
> new file mode 100644
> index 000000000000..5d411529f681
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/dp/dp_mst_drm.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-only
> + * Copyright (c) 2025 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#ifndef _DP_MST_DRM_H_
> +#define _DP_MST_DRM_H_
> +
> +#include "dp_display.h"
> +
> +int msm_dp_mst_init(struct msm_dp *dp_display, u32 max_streams, struct drm_dp_aux *drm_aux);
> +int msm_dp_mst_display_set_mgr_state(struct msm_dp *dp_display, bool state);
> +
> +#endif /* _DP_MST_DRM_H_ */
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 3061eca49cb2..5f73e0aa1c2f 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -363,6 +363,7 @@ bool msm_dp_needs_periph_flush(const struct msm_dp *dp_display,
>  			       const struct drm_display_mode *mode);
>  bool msm_dp_wide_bus_available(const struct msm_dp *dp_display);
>  int msm_dp_get_mst_max_stream(struct msm_dp *dp_display);
> +int msm_dp_mst_register(struct msm_dp *dp_display);
>  #else
>  static inline int __init msm_dp_register(void)
>  {
> @@ -384,6 +385,11 @@ static inline int msm_dp_get_mst_max_stream(struct msm_dp *dp_display)
>  	return -EINVAL;
>  }
>  
> +static inline int msm_dp_mst_register(struct msm_dp *dp_display)
> +{
> +	return -EINVAL;
> +}
> +
>  static inline void msm_dp_snapshot(struct msm_disp_state *disp_state, struct msm_dp *dp_display)
>  {
>  }
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry