[PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[Wayne Lin]

[Why]
Under DP daisy chain scenario as below:

	Src - Monitor_1 - Monitor_2

If unplug 2nd Monitor_2 and plug in again, observe that Monitor_1
doesn't light up.

When unplug 2nd monitor, we clear the
dc_link->cur_link_settings.lane_count in dm_dp_destroy_mst_connector().
However this link status is a shared data structure by all connected mst
monitors. Although the 2nd monitor is gone, this link status should
still be retained for other connected mst monitors. Otherwise, when we
plug the 2nd monitor in again, we find out that main link is not trained
and do link training again. Payload ID Table for Monitor_1 is ruined and
we don't reallocate it.

[How]
In dm_dp_destroy_mst_connector(), only clean the cur_link_settings when
we no longer do mst mode.

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 2c10352fa514..526f29598403 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -415,7 +415,10 @@ static void dm_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 					   aconnector->dc_sink);
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->dc_link->cur_link_settings.lane_count = 0;
+		mutex_lock(&mgr->lock);
+		if (!mgr->mst_state)
+			aconnector->dc_link->cur_link_settings.lane_count = 0;
+		mutex_unlock(&mgr->lock);
 	}
 
 	drm_connector_unregister(connector);
-- 
2.17.1

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Re: [PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[Rodrigo Siqueira]

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On 08/04, Wayne Lin wrote:
> [Why]
> Under DP daisy chain scenario as below:
> 
> 	Src - Monitor_1 - Monitor_2
> 
> If unplug 2nd Monitor_2 and plug in again, observe that Monitor_1
> doesn't light up.
> 
> When unplug 2nd monitor, we clear the
> dc_link->cur_link_settings.lane_count in dm_dp_destroy_mst_connector().
> However this link status is a shared data structure by all connected mst
> monitors. Although the 2nd monitor is gone, this link status should
> still be retained for other connected mst monitors. Otherwise, when we
> plug the 2nd monitor in again, we find out that main link is not trained
> and do link training again. Payload ID Table for Monitor_1 is ruined and
> we don't reallocate it.
> 
> [How]
> In dm_dp_destroy_mst_connector(), only clean the cur_link_settings when
> we no longer do mst mode.
> 
> Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 2c10352fa514..526f29598403 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -415,7 +415,10 @@ static void dm_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
>  					   aconnector->dc_sink);
>  		dc_sink_release(aconnector->dc_sink);
>  		aconnector->dc_sink = NULL;
> -		aconnector->dc_link->cur_link_settings.lane_count = 0;
> +		mutex_lock(&mgr->lock);
> +		if (!mgr->mst_state)
> +			aconnector->dc_link->cur_link_settings.lane_count = 0;
> +		mutex_unlock(&mgr->lock);
Hi Wayne,

The change looks good to me.

Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>

Just for curiosity, do you know why we use a mutex instead of
spin_lock_irq for this case? FWIU, the spin_lock_irq behavior looks
better for this sort of manipulation.

Thanks

>  	}
>  
>  	drm_connector_unregister(connector);
> -- 
> 2.17.1
> 

-- 
Rodrigo Siqueira
https://siqueira.tech

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RE: [PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[Lin, Wayne]

[AMD Public Use]



> -----Original Message-----
> From: Siqueira, Rodrigo <Rodrigo.Siqueira@amd.com>
> Sent: Wednesday, August 5, 2020 10:55 PM
> To: Lin, Wayne <Wayne.Lin@amd.com>
> Cc: amd-gfx@lists.freedesktop.org; Lakha, Bhawanpreet 
> <Bhawanpreet.Lakha@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; 
> Kazlauskas, Nicholas <Nicholas.Kazlauskas@amd.com>; Zuo, Jerry 
> <Jerry.Zuo@amd.com>
> Subject: Re: [PATCH] drm/amd/mst: clean DP main link status only when 
> unplug mst 1st link
> 
> On 08/04, Wayne Lin wrote:
> > [Why]
> > Under DP daisy chain scenario as below:
> >
> > 	Src - Monitor_1 - Monitor_2
> >
> > If unplug 2nd Monitor_2 and plug in again, observe that Monitor_1 
> > doesn't light up.
> >
> > When unplug 2nd monitor, we clear the 
> > dc_link->cur_link_settings.lane_count in dm_dp_destroy_mst_connector().
> > However this link status is a shared data structure by all connected 
> > mst monitors. Although the 2nd monitor is gone, this link status 
> > should still be retained for other connected mst monitors. 
> > Otherwise, when we plug the 2nd monitor in again, we find out that 
> > main link is not trained and do link training again. Payload ID 
> > Table for Monitor_1 is ruined and we don't reallocate it.
> >
> > [How]
> > In dm_dp_destroy_mst_connector(), only clean the cur_link_settings 
> > when we no longer do mst mode.
> >
> > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
> > ---
> >  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 5
> ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 2c10352fa514..526f29598403 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -415,7 +415,10 @@ static void dm_dp_destroy_mst_connector(struct
> drm_dp_mst_topology_mgr *mgr,
> >  					   aconnector->dc_sink);
> >  		dc_sink_release(aconnector->dc_sink);
> >  		aconnector->dc_sink = NULL;
> > -		aconnector->dc_link->cur_link_settings.lane_count = 0;
> > +		mutex_lock(&mgr->lock);
> > +		if (!mgr->mst_state)
> > +			aconnector->dc_link->cur_link_settings.lane_count = 0;
> > +		mutex_unlock(&mgr->lock);
> Hi Wayne,
> 
> The change looks good to me.
> 
> Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> 
> Just for curiosity, do you know why we use a mutex instead of 
> spin_lock_irq for this case? FWIU, the spin_lock_irq behavior looks 
> better for this sort of manipulation.

Hi Siqueira,

Thanks for your time.
AFAIK, changing mst_state (e.g. enabling MST mode) involves some reading/writing steps on DPCD which might cost some time. 
> 
> Thanks
> 
> >  	}
> >
> >  	drm_connector_unregister(connector);
> > --
> > 2.17.1
> >
> 
> --
> Rodrigo Siqueira
> https://siqueira.tech
--
Wayne Lin
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[PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[Wayne Lin]

[Why]
Under DP daisy chain scenario as below:

	Src - Monitor_1 - Monitor_2

If unplug 2nd Monitor_2 and plug in again, observe that Monitor_1
doesn't light up.

When unplug 2nd monitor, we clear the
dc_link->cur_link_settings.lane_count in dm_dp_destroy_mst_connector().
However this link status is a shared data structure by all connected mst
monitors. Although the 2nd monitor is gone, this link status should
still be retained for other connected mst monitors. Otherwise, when we
plug the 2nd monitor in again, we find out that main link is not trained
and do link training again. Payload ID Table for Monitor_1 is ruined and
we don't reallocate it.

[How]
In dm_dp_destroy_mst_connector(), only clean the cur_link_settings when
we no longer do mst mode.

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 2c10352fa514..526f29598403 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -415,7 +415,10 @@ static void dm_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 					   aconnector->dc_sink);
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
-		aconnector->dc_link->cur_link_settings.lane_count = 0;
+		mutex_lock(&mgr->lock);
+		if (!mgr->mst_state)
+			aconnector->dc_link->cur_link_settings.lane_count = 0;
+		mutex_unlock(&mgr->lock);
 	}
 
 	drm_connector_unregister(connector);
-- 
2.17.1

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RE: [PATCH] drm/amd/mst: clean DP main link status only when unplug mst 1st link

[Lin, Wayne]

[AMD Public Use]

Sorry for spamming. 
It's a duplicate one and should be ignored.

> -----Original Message-----
> From: Wayne Lin <Wayne.Lin@amd.com>
> Sent: Tuesday, August 4, 2020 11:37 AM
> To: amd-gfx@lists.freedesktop.org
> Cc: Pillai, Aurabindo <Aurabindo.Pillai@amd.com>; Wu, Hersen
> <hersenxs.wu@amd.com>; Kazlauskas, Nicholas
> <Nicholas.Kazlauskas@amd.com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira@amd.com>; Zuo, Jerry <Jerry.Zuo@amd.com>; Lin, Wayne
> <Wayne.Lin@amd.com>
> Subject: [PATCH] drm/amd/mst: clean DP main link status only when unplug
> mst 1st link
> 
> [Why]
> Under DP daisy chain scenario as below:
> 
> 	Src - Monitor_1 - Monitor_2
> 
> If unplug 2nd Monitor_2 and plug in again, observe that Monitor_1 doesn't
> light up.
> 
> When unplug 2nd monitor, we clear the
> dc_link->cur_link_settings.lane_count in dm_dp_destroy_mst_connector().
> However this link status is a shared data structure by all connected mst
> monitors. Although the 2nd monitor is gone, this link status should still be
> retained for other connected mst monitors. Otherwise, when we plug the 2nd
> monitor in again, we find out that main link is not trained and do link training
> again. Payload ID Table for Monitor_1 is ruined and we don't reallocate it.
> 
> [How]
> In dm_dp_destroy_mst_connector(), only clean the cur_link_settings when we
> no longer do mst mode.
> 
> Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 5
> ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 2c10352fa514..526f29598403 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -415,7 +415,10 @@ static void dm_dp_destroy_mst_connector(struct
> drm_dp_mst_topology_mgr *mgr,
>  					   aconnector->dc_sink);
>  		dc_sink_release(aconnector->dc_sink);
>  		aconnector->dc_sink = NULL;
> -		aconnector->dc_link->cur_link_settings.lane_count = 0;
> +		mutex_lock(&mgr->lock);
> +		if (!mgr->mst_state)
> +			aconnector->dc_link->cur_link_settings.lane_count = 0;
> +		mutex_unlock(&mgr->lock);
>  	}
> 
>  	drm_connector_unregister(connector);
> --
> 2.17.1
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