Re: [PATCH RESEND v5 17/25] drm/msm/dp: add link_ready to manage link-level operations

[Yongxing Mou <yongxing.mou@oss.qualcomm.com>]

On 7/13/2026 7:46 AM, Dmitry Baryshkov wrote:
> On Mon, Jun 29, 2026 at 10:14:38PM +0800, Yongxing Mou wrote:
>> In MST mode, multiple streams share the same DP link. Track a link_ready
>> state so msm_dp_display_prepare_link() runs only once per link and
>> repeated calls are skipped.
>>
>> 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_display.c | 42 ++++++++++++++++++++++++-------------
>>   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>>   2 files changed, 29 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 2a74302bcb7c..d56ee10ee065 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -702,6 +702,9 @@ int msm_dp_display_prepare_link(struct msm_dp *msm_dp_display)
>>   	if (msm_dp_display->is_edp)
>>   		msm_dp_hpd_plug_handle(dp);
>>   
>> +	if (msm_dp_display->link_ready)
>> +		return 0;
>> +
> 
> What kind of locking is protecting this variable? What prevents it from
> being accessed concurrently?
> 
In MST, the entire function is protected by mst_lock, so concurrent 
access to this variable is serialized.
>>   	rc = pm_runtime_resume_and_get(&msm_dp_display->pdev->dev);
>>   	if (rc) {
>>   		DRM_ERROR("failed to pm_runtime_resume\n");
>> @@ -714,14 +717,18 @@ int msm_dp_display_prepare_link(struct msm_dp *msm_dp_display)
>>   	if (!msm_dp_display->active_stream_cnt) {
>>   		msm_dp_display_host_phy_init(dp);
>>   		force_link_train = true;
>> +
>> +		rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel);
>> +		if (rc)
>> +			DRM_ERROR("Failed link training (rc=%d)\n", rc);
>> +		// TODO: schedule drm_connector_set_link_status_property()
>>   	}
>>   
>> -	rc = msm_dp_ctrl_on_link(dp->ctrl, dp->panel);
>> -	if (rc)
>> -		DRM_ERROR("Failed link training (rc=%d)\n", rc);
>> -	// TODO: schedule drm_connector_set_link_status_property()
> 
> Why is it being moved now rather than in the patch where
> active_stream_cnt was introduced?
> 
Got it. will move to that part
>> +	rc = msm_dp_ctrl_prepare_stream_on(dp->ctrl, dp->panel, force_link_train);
>> +	if (!rc)
>> +		msm_dp_display->link_ready = true;
>>   
>> -	return msm_dp_ctrl_prepare_stream_on(dp->ctrl, dp->panel, force_link_train);
>> +	return rc;
>>   }
>>   
>>   static int msm_dp_display_enable(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 676213a48089..0464f8941e8d 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.h
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
>> @@ -22,6 +22,7 @@ struct msm_dp {
>>   	bool mst_active;
>>   	unsigned int connector_type;
>>   	bool is_edp;
>> +	bool link_ready;
> 
> Please group the status variables together.
> 
Got it.
>>   
>>   	struct msm_dp_audio *msm_dp_audio;
>>   	bool psr_supported;
>>
>> -- 
>> 2.43.0
>>
>