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  3. [PATCH v2 00/12] drm/msm/dp: Drop the HPD state machine
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[PATCH v2 04/12] drm/msm/dp: Move link training to atomic_enable()

Jessica Zhang posted 12 patches 6 months ago
There is a newer version of this series
[PATCH v2 04/12] drm/msm/dp: Move link training to atomic_enable()
Posted by Jessica Zhang 6 months ago 
Currently, the DP link training is being done during HPD. Move
link training to atomic_enable() in accordance with the atomic_enable()
documentation.

Link disabling is already done in atomic_post_disable() (as part of the
dp_ctrl_off_link_stream() helper).

Finally, call the plug/unplug handlers directly in hpd_notify() instead
of queueing them in the event thread so that they aren't preempted by
other events.

Signed-off-by: Jessica Zhang <jessica.zhang@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index e2556de99894..c849befe58f0 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -427,11 +427,6 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
 	msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
 
 	msm_dp_link_reset_phy_params_vx_px(dp->link);
-	rc = msm_dp_ctrl_on_link(dp->ctrl);
-	if (rc) {
-		DRM_ERROR("failed to complete DP link training\n");
-		goto end;
-	}
 
 	msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);
 
@@ -1680,6 +1675,12 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
 		force_link_train = true;
 	}
 
+	rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
+	if (rc) {
+		DRM_ERROR("Failed link training (rc=%d)\n", rc);
+		dp->connector->state->link_status = DRM_LINK_STATUS_BAD;
+	}
+
 	msm_dp_display_enable(msm_dp_display, force_link_train);
 
 	rc = msm_dp_display_post_enable(dp);
@@ -1839,7 +1840,7 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
 		return;
 
 	if (!msm_dp_display->link_ready && status == connector_status_connected)
-		msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
+		msm_dp_hpd_plug_handle(dp, 0);
 	else if (msm_dp_display->link_ready && status == connector_status_disconnected)
-		msm_dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
+		msm_dp_hpd_unplug_handle(dp, 0);
 }

-- 
2.50.1
Re: [PATCH v2 04/12] drm/msm/dp: Move link training to atomic_enable()
Posted by Dmitry Baryshkov 6 months ago 
On 09/08/2025 03:35, Jessica Zhang wrote:
> Currently, the DP link training is being done during HPD. Move
> link training to atomic_enable() in accordance with the atomic_enable()
> documentation.
> 
> Link disabling is already done in atomic_post_disable() (as part of the
> dp_ctrl_off_link_stream() helper).
> 
> Finally, call the plug/unplug handlers directly in hpd_notify() instead
> of queueing them in the event thread so that they aren't preempted by
> other events.
> 
> Signed-off-by: Jessica Zhang <jessica.zhang@oss.qualcomm.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index e2556de99894..c849befe58f0 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -427,11 +427,6 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>   	msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>   
>   	msm_dp_link_reset_phy_params_vx_px(dp->link);
> -	rc = msm_dp_ctrl_on_link(dp->ctrl);
> -	if (rc) {
> -		DRM_ERROR("failed to complete DP link training\n");
> -		goto end;
> -	}
>   
>   	msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);

Also at this point we enqueue event, which will set link_ready to true 
(which is obviously incorrect).

>   
> @@ -1680,6 +1675,12 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
>   		force_link_train = true;
>   	}
>   
> +	rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
> +	if (rc) {
> +		DRM_ERROR("Failed link training (rc=%d)\n", rc);
> +		dp->connector->state->link_status = DRM_LINK_STATUS_BAD;

Add a comment why it's set directly rather than through 
drm_connector_set_link_status_property().


> +	}
> +
>   	msm_dp_display_enable(msm_dp_display, force_link_train);
>   
>   	rc = msm_dp_display_post_enable(dp);
> @@ -1839,7 +1840,7 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
>   		return;
>   
>   	if (!msm_dp_display->link_ready && status == connector_status_connected)
> -		msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
> +		msm_dp_hpd_plug_handle(dp, 0);
>   	else if (msm_dp_display->link_ready && status == connector_status_disconnected)
> -		msm_dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> +		msm_dp_hpd_unplug_handle(dp, 0);
>   }
> 


-- 
With best wishes
Dmitry
Re: [PATCH v2 04/12] drm/msm/dp: Move link training to atomic_enable()
Posted by Dmitry Baryshkov 6 months ago 
On 09/08/2025 03:35, Jessica Zhang wrote:
> Currently, the DP link training is being done during HPD. Move
> link training to atomic_enable() in accordance with the atomic_enable()
> documentation.
> 
> Link disabling is already done in atomic_post_disable() (as part of the
> dp_ctrl_off_link_stream() helper).
> 
> Finally, call the plug/unplug handlers directly in hpd_notify() instead
> of queueing them in the event thread so that they aren't preempted by
> other events.

This feels like two unrelated changes.

> 
> Signed-off-by: Jessica Zhang <jessica.zhang@oss.qualcomm.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++-------
>   1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index e2556de99894..c849befe58f0 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -427,11 +427,6 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>   	msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>   
>   	msm_dp_link_reset_phy_params_vx_px(dp->link);
> -	rc = msm_dp_ctrl_on_link(dp->ctrl);
> -	if (rc) {
> -		DRM_ERROR("failed to complete DP link training\n");
> -		goto end;
> -	}
>   
>   	msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);
>   
> @@ -1680,6 +1675,12 @@ void msm_dp_bridge_atomic_enable(struct drm_bridge *drm_bridge,
>   		force_link_train = true;
>   	}
>   
> +	rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
> +	if (rc) {
> +		DRM_ERROR("Failed link training (rc=%d)\n", rc);
> +		dp->connector->state->link_status = DRM_LINK_STATUS_BAD;
> +	}
> +
>   	msm_dp_display_enable(msm_dp_display, force_link_train);
>   
>   	rc = msm_dp_display_post_enable(dp);
> @@ -1839,7 +1840,7 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge *bridge,
>   		return;
>   
>   	if (!msm_dp_display->link_ready && status == connector_status_connected)
> -		msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
> +		msm_dp_hpd_plug_handle(dp, 0);
>   	else if (msm_dp_display->link_ready && status == connector_status_disconnected)
> -		msm_dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
> +		msm_dp_hpd_unplug_handle(dp, 0);
>   }
> 


-- 
With best wishes
Dmitry
Re: [PATCH v2 04/12] drm/msm/dp: Move link training to atomic_enable()
Posted by Jessica Zhang 6 months ago 

On 8/8/2025 5:45 PM, Dmitry Baryshkov wrote:
> On 09/08/2025 03:35, Jessica Zhang wrote:
>> Currently, the DP link training is being done during HPD. Move
>> link training to atomic_enable() in accordance with the atomic_enable()
>> documentation.
>>
>> Link disabling is already done in atomic_post_disable() (as part of the
>> dp_ctrl_off_link_stream() helper).
>>
>> Finally, call the plug/unplug handlers directly in hpd_notify() instead
>> of queueing them in the event thread so that they aren't preempted by
>> other events.
> 
> This feels like two unrelated changes.

Hi Dmitry,

Ack. Would it make more sense to squash the hpd_notify part with the IRQ 
thread change?

Thanks,

Jessica Zhang

> 
>>
>> Signed-off-by: Jessica Zhang <jessica.zhang@oss.qualcomm.com>
>> ---
>>   drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/ 
>> msm/dp/dp_display.c
>> index e2556de99894..c849befe58f0 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -427,11 +427,6 @@ static int msm_dp_display_process_hpd_high(struct 
>> msm_dp_display_private *dp)
>>       msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>>       msm_dp_link_reset_phy_params_vx_px(dp->link);
>> -    rc = msm_dp_ctrl_on_link(dp->ctrl);
>> -    if (rc) {
>> -        DRM_ERROR("failed to complete DP link training\n");
>> -        goto end;
>> -    }
>>       msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);
>> @@ -1680,6 +1675,12 @@ void msm_dp_bridge_atomic_enable(struct 
>> drm_bridge *drm_bridge,
>>           force_link_train = true;
>>       }
>> +    rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
>> +    if (rc) {
>> +        DRM_ERROR("Failed link training (rc=%d)\n", rc);
>> +        dp->connector->state->link_status = DRM_LINK_STATUS_BAD;
>> +    }
>> +
>>       msm_dp_display_enable(msm_dp_display, force_link_train);
>>       rc = msm_dp_display_post_enable(dp);
>> @@ -1839,7 +1840,7 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge 
>> *bridge,
>>           return;
>>       if (!msm_dp_display->link_ready && status == 
>> connector_status_connected)
>> -        msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
>> +        msm_dp_hpd_plug_handle(dp, 0);
>>       else if (msm_dp_display->link_ready && status == 
>> connector_status_disconnected)
>> -        msm_dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
>> +        msm_dp_hpd_unplug_handle(dp, 0);
>>   }
>>
> 
>

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