[PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Otherwise logs are filled with

  [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517

when the bridge isn't ready yet.

Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
Signed-off-by: Guido Günther <agx@sigxcpu.org>
---
 drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index a8ed66751c2d..f0508e85ae98 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
 	bridge->encoder = NULL;
 	list_del(&bridge->chain_node);
 
+	if (ret != -EPROBE_DEFER) {
 #ifdef CONFIG_OF
-	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
-		  bridge->of_node, encoder->name, ret);
+		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
+			  bridge->of_node, encoder->name, ret);
 #else
-	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
-		  encoder->name, ret);
+		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
+			  encoder->name, ret);
 #endif
-
+	}
 	return ret;
 }
 EXPORT_SYMBOL(drm_bridge_attach);
-- 
2.33.0

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Laurent Pinchart]

Hi Guido,

Thank you for the patch.

On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
> Otherwise logs are filled with
> 
>   [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
> 
> when the bridge isn't ready yet.
> 
> Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
> Signed-off-by: Guido Günther <agx@sigxcpu.org>
> ---
>  drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index a8ed66751c2d..f0508e85ae98 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  	bridge->encoder = NULL;
>  	list_del(&bridge->chain_node);
>  
> +	if (ret != -EPROBE_DEFER) {
>  #ifdef CONFIG_OF
> -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> -		  bridge->of_node, encoder->name, ret);
> +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> +			  bridge->of_node, encoder->name, ret);
>  #else
> -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> -		  encoder->name, ret);
> +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> +			  encoder->name, ret);
>  #endif
> -
> +	}

This looks fine as such, but I'm concerned about the direction it's
taking. Ideally, probe deferral should happen at probe time, way before
the bridge is attached. Doing otherwise is a step in the wrong direction
in my opinion, and something we'll end up regretting when we'll feel the
pain it inflicts.

>  	return ret;
>  }
>  EXPORT_SYMBOL(drm_bridge_attach);

-- 
Regards,

Laurent Pinchart

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Hi,
On Tue, Oct 12, 2021 at 10:08:28PM +0200, Sam Ravnborg wrote:
> Hi Guido,
> 
> On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
> > Otherwise logs are filled with
> > 
> >   [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
> > 
> > when the bridge isn't ready yet.
> > 
> > Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
> > Signed-off-by: Guido Günther <agx@sigxcpu.org>
> > ---
> >  drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index a8ed66751c2d..f0508e85ae98 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> >  	bridge->encoder = NULL;
> >  	list_del(&bridge->chain_node);
> >  
> > +	if (ret != -EPROBE_DEFER) {
> >  #ifdef CONFIG_OF
> > -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > -		  bridge->of_node, encoder->name, ret);
> > +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > +			  bridge->of_node, encoder->name, ret);
> 
> It would be better to use drm_probe_err().

That's what i thought initially but since the rest here uses DRM_*
logging i stuck with it. Happy to change that though.
Cheers,
 -- Guido

> 
> 	Sam
> 
> >  #else
> > -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > -		  encoder->name, ret);
> > +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > +			  encoder->name, ret);
> >  #endif
> > -
> > +	}
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(drm_bridge_attach);
> > -- 
> > 2.33.0
> 

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Hi Laurent,
On Tue, Oct 12, 2021 at 11:17:07PM +0300, Laurent Pinchart wrote:
> Hi Guido,
> 
> Thank you for the patch.
> 
> On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
> > Otherwise logs are filled with
> > 
> >   [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
> > 
> > when the bridge isn't ready yet.
> > 
> > Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
> > Signed-off-by: Guido Günther <agx@sigxcpu.org>
> > ---
> >  drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index a8ed66751c2d..f0508e85ae98 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> >  	bridge->encoder = NULL;
> >  	list_del(&bridge->chain_node);
> >  
> > +	if (ret != -EPROBE_DEFER) {
> >  #ifdef CONFIG_OF
> > -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > -		  bridge->of_node, encoder->name, ret);
> > +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > +			  bridge->of_node, encoder->name, ret);
> >  #else
> > -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > -		  encoder->name, ret);
> > +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > +			  encoder->name, ret);
> >  #endif
> > -
> > +	}
> 
> This looks fine as such, but I'm concerned about the direction it's
> taking. Ideally, probe deferral should happen at probe time, way before
> the bridge is attached. Doing otherwise is a step in the wrong direction
> in my opinion, and something we'll end up regretting when we'll feel the
> pain it inflicts.

The particular case I'm seeing this is the nwl driver probe deferrals if
the panel bridge isn't ready (which needs a bunch of components
(dsi, panel, backlight wrapped led, ...) and it probes fine later on so I
wonder where you see the actual error cause? That downstream of the
bridge isn't ready or that the display controller is already attaching
the bridge?

Cheers,
 -- Guido

> 
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL(drm_bridge_attach);
> 
> -- 
> Regards,
> 
> Laurent Pinchart
> 

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Hi,
On Tue, Oct 12, 2021 at 10:47:14PM +0200, Guido Günther wrote:
> Hi Laurent,
> On Tue, Oct 12, 2021 at 11:17:07PM +0300, Laurent Pinchart wrote:
> > Hi Guido,
> > 
> > Thank you for the patch.
> > 
> > On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
> > > Otherwise logs are filled with
> > > 
> > >   [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
> > > 
> > > when the bridge isn't ready yet.
> > > 
> > > Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
> > > Signed-off-by: Guido Günther <agx@sigxcpu.org>
> > > ---
> > >  drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
> > >  1 file changed, 6 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > > index a8ed66751c2d..f0508e85ae98 100644
> > > --- a/drivers/gpu/drm/drm_bridge.c
> > > +++ b/drivers/gpu/drm/drm_bridge.c
> > > @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> > >  	bridge->encoder = NULL;
> > >  	list_del(&bridge->chain_node);
> > >  
> > > +	if (ret != -EPROBE_DEFER) {
> > >  #ifdef CONFIG_OF
> > > -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > -		  bridge->of_node, encoder->name, ret);
> > > +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > +			  bridge->of_node, encoder->name, ret);
> > >  #else
> > > -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > > -		  encoder->name, ret);
> > > +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > > +			  encoder->name, ret);
> > >  #endif
> > > -
> > > +	}
> > 
> > This looks fine as such, but I'm concerned about the direction it's
> > taking. Ideally, probe deferral should happen at probe time, way before
> > the bridge is attached. Doing otherwise is a step in the wrong direction
> > in my opinion, and something we'll end up regretting when we'll feel the
> > pain it inflicts.
> 
> The particular case I'm seeing this is the nwl driver probe deferrals if
> the panel bridge isn't ready (which needs a bunch of components
> (dsi, panel, backlight wrapped led, ...) and it probes fine later on so I
> wonder where you see the actual error cause? That downstream of the
> bridge isn't ready or that the display controller is already attaching
> the bridge?

I should add that mxsfb does a `dev_err_probe()` already when checking
the return value of `drm_bridge_attach()` so the error printed is
triggered by the additional check added in the above function while the
code path already ignored -EPROBE_DEFER before. This looks sensible to
me since upper layers can't known when all the downstream bridges are
done probing or am I missing something?

Cheers,
 -- Guido

> 
> Cheers,
>  -- Guido
> 
> > 
> > >  	return ret;
> > >  }
> > >  EXPORT_SYMBOL(drm_bridge_attach);
> > 
> > -- 
> > Regards,
> > 
> > Laurent Pinchart
> > 

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Andrzej Hajda]

On 12.10.2021 22:47, Guido Günther wrote:
> Hi Laurent,
> On Tue, Oct 12, 2021 at 11:17:07PM +0300, Laurent Pinchart wrote:
>> Hi Guido,
>>
>> Thank you for the patch.
>>
>> On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
>>> Otherwise logs are filled with
>>>
>>>    [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
>>>
>>> when the bridge isn't ready yet.
>>>
>>> Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
>>> Signed-off-by: Guido Günther <agx@sigxcpu.org>
>>> ---
>>>   drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
>>>   1 file changed, 6 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
>>> index a8ed66751c2d..f0508e85ae98 100644
>>> --- a/drivers/gpu/drm/drm_bridge.c
>>> +++ b/drivers/gpu/drm/drm_bridge.c
>>> @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>>>   	bridge->encoder = NULL;
>>>   	list_del(&bridge->chain_node);
>>>   
>>> +	if (ret != -EPROBE_DEFER) {
>>>   #ifdef CONFIG_OF
>>> -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
>>> -		  bridge->of_node, encoder->name, ret);
>>> +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
>>> +			  bridge->of_node, encoder->name, ret);
>>>   #else
>>> -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
>>> -		  encoder->name, ret);
>>> +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
>>> +			  encoder->name, ret);
>>>   #endif
>>> -
>>> +	}
>>
>> This looks fine as such, but I'm concerned about the direction it's
>> taking. Ideally, probe deferral should happen at probe time, way before
>> the bridge is attached. Doing otherwise is a step in the wrong direction
>> in my opinion, and something we'll end up regretting when we'll feel the
>> pain it inflicts.
> 
> The particular case I'm seeing this is the nwl driver probe deferrals if
> the panel bridge isn't ready (which needs a bunch of components
> (dsi, panel, backlight wrapped led, ...) and it probes fine later on so I
> wonder where you see the actual error cause? That downstream of the
> bridge isn't ready or that the display controller is already attaching
> the bridge?

So it is something wrong there, nwl should not publish bridge interface 
until it gather its resources (the panel in this case).

Regards
Andrzej


> 
> Cheers,
>   -- Guido
> 
>>
>>>   	return ret;
>>>   }
>>>   EXPORT_SYMBOL(drm_bridge_attach);
>>
>> -- 
>> Regards,
>>
>> Laurent Pinchart
>>

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Hi,
On Wed, Oct 13, 2021 at 08:48:32AM +0200, Andrzej Hajda wrote:
> On 12.10.2021 22:47, Guido Günther wrote:
> > Hi Laurent,
> > On Tue, Oct 12, 2021 at 11:17:07PM +0300, Laurent Pinchart wrote:
> > > Hi Guido,
> > > 
> > > Thank you for the patch.
> > > 
> > > On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
> > > > Otherwise logs are filled with
> > > > 
> > > >    [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
> > > > 
> > > > when the bridge isn't ready yet.
> > > > 
> > > > Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
> > > > Signed-off-by: Guido Günther <agx@sigxcpu.org>
> > > > ---
> > > >   drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
> > > >   1 file changed, 6 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > > > index a8ed66751c2d..f0508e85ae98 100644
> > > > --- a/drivers/gpu/drm/drm_bridge.c
> > > > +++ b/drivers/gpu/drm/drm_bridge.c
> > > > @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
> > > >   	bridge->encoder = NULL;
> > > >   	list_del(&bridge->chain_node);
> > > > +	if (ret != -EPROBE_DEFER) {
> > > >   #ifdef CONFIG_OF
> > > > -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > > -		  bridge->of_node, encoder->name, ret);
> > > > +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > > +			  bridge->of_node, encoder->name, ret);
> > > >   #else
> > > > -	DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > > > -		  encoder->name, ret);
> > > > +		DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
> > > > +			  encoder->name, ret);
> > > >   #endif
> > > > -
> > > > +	}
> > > 
> > > This looks fine as such, but I'm concerned about the direction it's
> > > taking. Ideally, probe deferral should happen at probe time, way before
> > > the bridge is attached. Doing otherwise is a step in the wrong direction
> > > in my opinion, and something we'll end up regretting when we'll feel the
> > > pain it inflicts.
> > 
> > The particular case I'm seeing this is the nwl driver probe deferrals if
> > the panel bridge isn't ready (which needs a bunch of components
> > (dsi, panel, backlight wrapped led, ...) and it probes fine later on so I
> > wonder where you see the actual error cause? That downstream of the
> > bridge isn't ready or that the display controller is already attaching
> > the bridge?
> 
> So it is something wrong there, nwl should not publish bridge interface
> until it gather its resources (the panel in this case).

That helps, I'll look at that. Thanks!
 -- Guido

> 
> Regards
> Andrzej
> 
> 
> > 
> > Cheers,
> >   -- Guido
> > 
> > > 
> > > >   	return ret;
> > > >   }
> > > >   EXPORT_SYMBOL(drm_bridge_attach);
> > > 
> > > -- 
> > > Regards,
> > > 
> > > Laurent Pinchart
> > > 
> 

Re: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails

[Guido Günther]

Hi Sam,
On Thu, Oct 14, 2021 at 09:35:20PM +0200, Sam Ravnborg wrote:
> Hi Guido,
> 
> > > >  
> > > > +	if (ret != -EPROBE_DEFER) {
> > > >  #ifdef CONFIG_OF
> > > > -	DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > > -		  bridge->of_node, encoder->name, ret);
> > > > +		DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
> > > > +			  bridge->of_node, encoder->name, ret);
> > > 
> > > It would be better to use drm_probe_err().
> > 
> > That's what i thought initially but since the rest here uses DRM_*
> > logging i stuck with it. Happy to change that though.
> 
> If we continue to use the deprecated DRM_ logging functions then we will
> never get rid of them. And then I like the simplicity of
> drm_probe_err().

I wasn't aware those are deprecated. I'll fix that up in case this patch
is needed, which

https://lore.kernel.org/dri-devel/CAMty3ZAsn4K0WFRC_FNN2Mina0gSu4Nc1y1zVsoZ8GuSqcQFsA@mail.gmail.com/

makes it a bit look like it.
Cheers,
  -- Guido

> 
> In the end it is up to you.
> 
> 	Sam
>