[PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Lyude Paul]

Userspace asked them to be forced off, so why would we care about what a
probe tells us?

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_probe_helper.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index a1bb157bfdfa..56d2b5dd1f58 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -269,7 +269,9 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
 retry:
 	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
 	if (!ret) {
-		if (funcs->detect_ctx)
+		if (connector->force == DRM_FORCE_OFF)
+			ret = connector_status_disconnected;
+		else if (funcs->detect_ctx)
 			ret = funcs->detect_ctx(connector, &ctx, force);
 		else if (connector->funcs->detect)
 			ret = connector->funcs->detect(connector, force);
@@ -317,6 +319,9 @@ drm_helper_probe_detect(struct drm_connector *connector,
 	if (ret)
 		return ret;
 
+	if (connector->force == DRM_FORCE_OFF)
+		return connector_status_disconnected;
+
 	if (funcs->detect_ctx)
 		return funcs->detect_ctx(connector, ctx, force);
 	else if (connector->funcs->detect)
-- 
2.17.1

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Ville Syrjälä]

On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> Userspace asked them to be forced off, so why would we care about what a
> probe tells us?

I believe there should be force checks in the callers already.
Or are we missing some?

> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> ---
>  drivers/gpu/drm/drm_probe_helper.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index a1bb157bfdfa..56d2b5dd1f58 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -269,7 +269,9 @@ drm_helper_probe_detect_ctx(struct drm_connector *connector, bool force)
>  retry:
>  	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex, &ctx);
>  	if (!ret) {
> -		if (funcs->detect_ctx)
> +		if (connector->force == DRM_FORCE_OFF)
> +			ret = connector_status_disconnected;

connector->force is protected by mode_config.mutex IIRC.

> +		else if (funcs->detect_ctx)
>  			ret = funcs->detect_ctx(connector, &ctx, force);
>  		else if (connector->funcs->detect)
>  			ret = connector->funcs->detect(connector, force);
> @@ -317,6 +319,9 @@ drm_helper_probe_detect(struct drm_connector *connector,
>  	if (ret)
>  		return ret;
>  
> +	if (connector->force == DRM_FORCE_OFF)
> +		return connector_status_disconnected;
> +
>  	if (funcs->detect_ctx)
>  		return funcs->detect_ctx(connector, ctx, force);
>  	else if (connector->funcs->detect)
> -- 
> 2.17.1
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Lyude Paul]

On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > Userspace asked them to be forced off, so why would we care about what a
> > probe tells us?
> 
> I believe there should be force checks in the callers already.
> Or are we missing some?

JFYI, this is to fix "DDC responded but no EDID" errors from nouveau, which
presumably come from the fact that having a connector forced off disables
reading it's EDID. It's possible we are missing something in
nouveau_connector_detect(), but I'm confused as to why we would want to call
->probe() at all in the first place
> 
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > ---
> >  drivers/gpu/drm/drm_probe_helper.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c
> > b/drivers/gpu/drm/drm_probe_helper.c
> > index a1bb157bfdfa..56d2b5dd1f58 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -269,7 +269,9 @@ drm_helper_probe_detect_ctx(struct drm_connector
> > *connector, bool force)
> >  retry:
> >  	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex,
> > &ctx);
> >  	if (!ret) {
> > -		if (funcs->detect_ctx)
> > +		if (connector->force == DRM_FORCE_OFF)
> > +			ret = connector_status_disconnected;
> 
> connector->force is protected by mode_config.mutex IIRC.
> 
> > +		else if (funcs->detect_ctx)
> >  			ret = funcs->detect_ctx(connector, &ctx, force);
> >  		else if (connector->funcs->detect)
> >  			ret = connector->funcs->detect(connector, force);
> > @@ -317,6 +319,9 @@ drm_helper_probe_detect(struct drm_connector *connector,
> >  	if (ret)
> >  		return ret;
> >  
> > +	if (connector->force == DRM_FORCE_OFF)
> > +		return connector_status_disconnected;
> > +
> >  	if (funcs->detect_ctx)
> >  		return funcs->detect_ctx(connector, ctx, force);
> >  	else if (connector->funcs->detect)
> > -- 
> > 2.17.1
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> 

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Lyude Paul]

On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > Userspace asked them to be forced off, so why would we care about what a
> > probe tells us?
> 
> I believe there should be force checks in the callers already.
> Or are we missing some?

JFYI, what triggered me to send this patch are these error messages that come
from nouveau when a hotplug happens on a port that we've forced off:

[ 1903.918104] nouveau 0000:01:00.0: DRM: DDC responded, but no EDID for DP-2
[ 1903.918123] [drm:drm_helper_hpd_irq_event [drm_kms_helper]] [CONNECTOR:61:DP-2] status updated from disconnected to disconnected

That being said; I'm sure there are probably some checks missing, but I don't
really see the purpose in calling the driver's probe functions at all if they're
just supposed to return the status we forced.

> 
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > ---
> >  drivers/gpu/drm/drm_probe_helper.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c
> > b/drivers/gpu/drm/drm_probe_helper.c
> > index a1bb157bfdfa..56d2b5dd1f58 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -269,7 +269,9 @@ drm_helper_probe_detect_ctx(struct drm_connector
> > *connector, bool force)
> >  retry:
> >  	ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex,
> > &ctx);
> >  	if (!ret) {
> > -		if (funcs->detect_ctx)
> > +		if (connector->force == DRM_FORCE_OFF)
> > +			ret = connector_status_disconnected;
> 
> connector->force is protected by mode_config.mutex IIRC.
> 
> > +		else if (funcs->detect_ctx)
> >  			ret = funcs->detect_ctx(connector, &ctx, force);
> >  		else if (connector->funcs->detect)
> >  			ret = connector->funcs->detect(connector, force);
> > @@ -317,6 +319,9 @@ drm_helper_probe_detect(struct drm_connector *connector,
> >  	if (ret)
> >  		return ret;
> >  
> > +	if (connector->force == DRM_FORCE_OFF)
> > +		return connector_status_disconnected;
> > +
> >  	if (funcs->detect_ctx)
> >  		return funcs->detect_ctx(connector, ctx, force);
> >  	else if (connector->funcs->detect)
> > -- 
> > 2.17.1
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> 

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Ville Syrjälä]

On Mon, Sep 17, 2018 at 02:10:02PM -0400, Lyude Paul wrote:
> On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> > On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > > Userspace asked them to be forced off, so why would we care about what a
> > > probe tells us?
> > 
> > I believe there should be force checks in the callers already.
> > Or are we missing some?
> 
> JFYI, what triggered me to send this patch are these error messages that come
> from nouveau when a hotplug happens on a port that we've forced off:
> 
> [ 1903.918104] nouveau 0000:01:00.0: DRM: DDC responded, but no EDID for DP-2
> [ 1903.918123] [drm:drm_helper_hpd_irq_event [drm_kms_helper]] [CONNECTOR:61:DP-2] status updated from disconnected to disconnected
> 
> That being said; I'm sure there are probably some checks missing, but I don't
> really see the purpose in calling the driver's probe functions at all if they're
> just supposed to return the status we forced.

Digging through my cobweb ridden local git repository I found this:

commit bbd17813a7c7d0210c619365707044d0fb29e3f0
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Mon Jun 10 15:28:55 2013 +0300

    drm: Ignore forced connectors in drm_helper_hpd_irq_event()
    
    drm_helper_hpd_irq_event() calls the connector's .detect() function
    even for forced connectors. If the returned status doesn't match the
    forced status, we will send the hotplug event, causing userspace to
    re-probe all the connectors. Eventually we should end up back where
    we started when drm_helper_probe_single_connector_modes() overwrites
    the connector status with the forced status.
    
    We can avoid all that pointles work if we just skip forced connectors
    in drm_helper_hpd_irq_event().
    
    Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index ed1334e27c33..4fc2ad76c107 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -1086,6 +1086,10 @@ void drm_helper_hpd_irq_event(struct drm_device *dev)
 	mutex_lock(&dev->mode_config.mutex);
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
 
+		/* Ignore forced connectors. */
+		if (connector->force)
+			continue;
+
 		/* Only handle HPD capable connectors. */
 		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
 			continue;


I guess I never sent it out.

-- 
Ville Syrjälä
Intel

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Lyude Paul]

On Mon, 2018-09-17 at 21:16 +0300, Ville Syrjälä wrote:
> On Mon, Sep 17, 2018 at 02:10:02PM -0400, Lyude Paul wrote:
> > On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> > > On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > > > Userspace asked them to be forced off, so why would we care about what a
> > > > probe tells us?
> > > 
> > > I believe there should be force checks in the callers already.
> > > Or are we missing some?
> > 
> > JFYI, what triggered me to send this patch are these error messages that
> > come
> > from nouveau when a hotplug happens on a port that we've forced off:
> > 
> > [ 1903.918104] nouveau 0000:01:00.0: DRM: DDC responded, but no EDID for DP-
> > 2
> > [ 1903.918123] [drm:drm_helper_hpd_irq_event [drm_kms_helper]]
> > [CONNECTOR:61:DP-2] status updated from disconnected to disconnected
> > 
> > That being said; I'm sure there are probably some checks missing, but I
> > don't
> > really see the purpose in calling the driver's probe functions at all if
> > they're
> > just supposed to return the status we forced.
> 
> Digging through my cobweb ridden local git repository I found this:
> 
> commit bbd17813a7c7d0210c619365707044d0fb29e3f0
> Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Date:   Mon Jun 10 15:28:55 2013 +0300
> 
>     drm: Ignore forced connectors in drm_helper_hpd_irq_event()
>     
>     drm_helper_hpd_irq_event() calls the connector's .detect() function
>     even for forced connectors. If the returned status doesn't match the
>     forced status, we will send the hotplug event, causing userspace to
>     re-probe all the connectors. Eventually we should end up back where
>     we started when drm_helper_probe_single_connector_modes() overwrites
>     the connector status with the forced status.
>     
>     We can avoid all that pointles work if we just skip forced connectors
>     in drm_helper_hpd_irq_event().
>     
>     Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> diff --git a/drivers/gpu/drm/drm_crtc_helper.c
> b/drivers/gpu/drm/drm_crtc_helper.c
> index ed1334e27c33..4fc2ad76c107 100644
> --- a/drivers/gpu/drm/drm_crtc_helper.c
> +++ b/drivers/gpu/drm/drm_crtc_helper.c
> @@ -1086,6 +1086,10 @@ void drm_helper_hpd_irq_event(struct drm_device *dev)
>  	mutex_lock(&dev->mode_config.mutex);
>  	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
>  
> +		/* Ignore forced connectors. */
> +		if (connector->force)
> +			continue;
> +
>  		/* Only handle HPD capable connectors. */
>  		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
>  			continue;
> 
> 
> I guess I never sent it out.

Ahhh, to be honest though this patch isn't really enough.
drm_helper_hpd_irq_event() isn't going to be used by all drivers (I may remove
some usage of it in nouveau in the near future, even) so I still think it would
be a better idea to just add this into drm_helper_probe_detect() and
drm_helper_probe_detect_ctx() so everything gets covered

> 

Re: [PATCH] drm/probe_helper: Don't bother probing when connectors are forced off

[Daniel Vetter]

On Mon, Sep 17, 2018 at 05:12:04PM -0400, Lyude Paul wrote:
> On Mon, 2018-09-17 at 21:16 +0300, Ville Syrjälä wrote:
> > On Mon, Sep 17, 2018 at 02:10:02PM -0400, Lyude Paul wrote:
> > > On Mon, 2018-09-17 at 20:55 +0300, Ville Syrjälä wrote:
> > > > On Mon, Sep 17, 2018 at 01:43:44PM -0400, Lyude Paul wrote:
> > > > > Userspace asked them to be forced off, so why would we care about what a
> > > > > probe tells us?
> > > > 
> > > > I believe there should be force checks in the callers already.
> > > > Or are we missing some?
> > > 
> > > JFYI, what triggered me to send this patch are these error messages that
> > > come
> > > from nouveau when a hotplug happens on a port that we've forced off:
> > > 
> > > [ 1903.918104] nouveau 0000:01:00.0: DRM: DDC responded, but no EDID for DP-
> > > 2
> > > [ 1903.918123] [drm:drm_helper_hpd_irq_event [drm_kms_helper]]
> > > [CONNECTOR:61:DP-2] status updated from disconnected to disconnected
> > > 
> > > That being said; I'm sure there are probably some checks missing, but I
> > > don't
> > > really see the purpose in calling the driver's probe functions at all if
> > > they're
> > > just supposed to return the status we forced.
> > 
> > Digging through my cobweb ridden local git repository I found this:
> > 
> > commit bbd17813a7c7d0210c619365707044d0fb29e3f0
> > Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Date:   Mon Jun 10 15:28:55 2013 +0300
> > 
> >     drm: Ignore forced connectors in drm_helper_hpd_irq_event()
> >     
> >     drm_helper_hpd_irq_event() calls the connector's .detect() function
> >     even for forced connectors. If the returned status doesn't match the
> >     forced status, we will send the hotplug event, causing userspace to
> >     re-probe all the connectors. Eventually we should end up back where
> >     we started when drm_helper_probe_single_connector_modes() overwrites
> >     the connector status with the forced status.
> >     
> >     We can avoid all that pointles work if we just skip forced connectors
> >     in drm_helper_hpd_irq_event().
> >     
> >     Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > diff --git a/drivers/gpu/drm/drm_crtc_helper.c
> > b/drivers/gpu/drm/drm_crtc_helper.c
> > index ed1334e27c33..4fc2ad76c107 100644
> > --- a/drivers/gpu/drm/drm_crtc_helper.c
> > +++ b/drivers/gpu/drm/drm_crtc_helper.c
> > @@ -1086,6 +1086,10 @@ void drm_helper_hpd_irq_event(struct drm_device *dev)
> >  	mutex_lock(&dev->mode_config.mutex);
> >  	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
> >  
> > +		/* Ignore forced connectors. */
> > +		if (connector->force)
> > +			continue;
> > +
> >  		/* Only handle HPD capable connectors. */
> >  		if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
> >  			continue;
> > 
> > 
> > I guess I never sent it out.
> 
> Ahhh, to be honest though this patch isn't really enough.
> drm_helper_hpd_irq_event() isn't going to be used by all drivers (I may remove
> some usage of it in nouveau in the near future, even) so I still think it would
> be a better idea to just add this into drm_helper_probe_detect() and
> drm_helper_probe_detect_ctx() so everything gets covered

Atm all connector->force handling is outside of drm_helper_probe_detect. I
guess we could try to push (some) of it into this helper, if that's
useful. There seems to be some duplication already. But adding a redundant
check like you do here feels a bit funky.  Maybe makes more sense in
context of the nouveau stuff you're working on?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch