[3/6] drm/sun4i: dsi: Add bridge support

Some display panels would come up with a non-DSI output which
can have an option to connect DSI interface by means of bridge
convertor.

This DSI to non-DSI bridge convertor would require a bridge
driver that would communicate the DSI controller for bridge
functionalities.

So, add support for bridge functionalities in Allwinner DSI
controller.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
 2 files changed, 49 insertions(+), 17 deletions(-)
  

Hi,

On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
> Some display panels would come up with a non-DSI output which
> can have an option to connect DSI interface by means of bridge
> convertor.
> 
> This DSI to non-DSI bridge convertor would require a bridge
> driver that would communicate the DSI controller for bridge
> functionalities.
> 
> So, add support for bridge functionalities in Allwinner DSI
> controller.

See a few comments below.

> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> ---
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
>  2 files changed, 49 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 0960b96b62cc..64d74313b842 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel))
>  		drm_panel_prepare(dsi->panel);
>  
> +	if (!IS_ERR(dsi->bridge))
> +		drm_bridge_pre_enable(dsi->bridge);
> +
>  	/*
>  	 * FIXME: This should be moved after the switch to HS mode.
>  	 *
> @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel))
>  		drm_panel_enable(dsi->panel);
>  
> +	if (!IS_ERR(dsi->bridge))
> +		drm_bridge_enable(dsi->bridge);
> +
>  	sun6i_dsi_start(dsi, DSI_START_HSC);
>  
>  	udelay(1000);
> @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
>  	if (!IS_ERR(dsi->panel)) {
>  		drm_panel_disable(dsi->panel);
>  		drm_panel_unprepare(dsi->panel);
> +	} else if (!IS_ERR(dsi->bridge)) {
> +		drm_bridge_disable(dsi->bridge);
> +		drm_bridge_post_disable(dsi->bridge);
>  	}
>  
>  	phy_power_off(dsi->dphy);
> @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
>  	struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
>  
>  	dsi->device = device;
> -	dsi->panel = of_drm_find_panel(device->dev.of_node);
> -	if (IS_ERR(dsi->panel))
> -		return PTR_ERR(dsi->panel);
>  
> -	dev_info(host->dev, "Attached device %s\n", device->name);
> +	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> +	if (!dsi->bridge) {

You are using IS_ERR to check that the bridge is alive in the changes
above, but switch to checking that it's non-NULL at this point.

Are both guaranteed to be interchangeable?

> +		dsi->panel = of_drm_find_panel(device->dev.of_node);
> +		if (IS_ERR(dsi->panel))
> +			return PTR_ERR(dsi->panel);
> +	}

You should probably use drm_of_find_panel_or_bridge instead of
duplicating the logic here.

> +	dev_info(host->dev, "Attached %s %s\n",
> +		 dsi->bridge ? "bridge" : "panel", device->name);
>  
>  	return 0;
>  }
> @@ -1055,8 +1069,10 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
>  	struct sun4i_tcon *tcon0 = sun4i_get_tcon0(drm);
>  	int ret;
>  
> -	if (!dsi->panel)
> +	if (!(dsi->panel || dsi->bridge)) {
> +		dev_info(drm->dev, "No panel or bridge found... DSI output disabled\n");
>  		return -EPROBE_DEFER;
> +	}
>  
>  	dsi->drv = drv;
>  
> @@ -1078,19 +1094,29 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
>  	}
>  	dsi->encoder.possible_crtcs = BIT(0);
>  
> -	drm_connector_helper_add(&dsi->connector,
> -				 &sun6i_dsi_connector_helper_funcs);
> -	ret = drm_connector_init(drm, &dsi->connector,
> -				 &sun6i_dsi_connector_funcs,
> -				 DRM_MODE_CONNECTOR_DSI);
> -	if (ret) {
> -		dev_err(dsi->dev,
> -			"Couldn't initialise the DSI connector\n");
> -		goto err_cleanup_connector;
> +	if (dsi->panel) {
> +		drm_connector_helper_add(&dsi->connector,
> +					 &sun6i_dsi_connector_helper_funcs);
> +		ret = drm_connector_init(drm, &dsi->connector,
> +					 &sun6i_dsi_connector_funcs,
> +					 DRM_MODE_CONNECTOR_DSI);
> +		if (ret) {
> +			dev_err(dsi->dev,
> +				"Couldn't initialise the DSI connector\n");
> +			goto err_cleanup_connector;
> +		}
> +
> +		drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> +		drm_panel_attach(dsi->panel, &dsi->connector);
>  	}
>  
> -	drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
> -	drm_panel_attach(dsi->panel, &dsi->connector);
> +	if (dsi->bridge) {
> +		ret = drm_bridge_attach(&dsi->encoder, dsi->bridge, NULL);
> +		if (ret) {
> +			dev_err(dsi->dev, "Couldn't attach the DSI bridge\n");
> +			goto err_cleanup_connector;
> +		}
> +	}
>  
>  	return 0;
>  
> @@ -1104,7 +1130,12 @@ static void sun6i_dsi_unbind(struct device *dev, struct device *master,
>  {
>  	struct sun6i_dsi *dsi = dev_get_drvdata(dev);
>  
> -	drm_panel_detach(dsi->panel);
> +	if (dsi->panel)
> +		drm_panel_detach(dsi->panel);
> +
> +	if (dsi->bridge)
> +		drm_bridge_detach(dsi->bridge);

As I mentionned in the first patch, this is quite suspicious since the
DRM core should be in charge of detaching the bridge, not the driver.

Cheers,

Paul

> +
>  }
>  
>  static const struct component_ops sun6i_dsi_ops = {
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> index 5c4983212f89..76874ff8e3ef 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> @@ -36,6 +36,7 @@ struct sun6i_dsi {
>  	struct sun4i_tcon	*tcon;
>  	struct mipi_dsi_device	*device;
>  	struct drm_panel	*panel;
> +	struct drm_bridge	*bridge;
>  	const struct sun6i_dsi_variant	*variant;
>  };
>  
> -- 
> 2.18.0.321.gffc6fa0e3
>
  

On Fri, Mar 15, 2019 at 02:32:55PM +0100, Paul Kocialkowski wrote:
> Hi,
> 
> On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
> > Some display panels would come up with a non-DSI output which
> > can have an option to connect DSI interface by means of bridge
> > convertor.
> > 
> > This DSI to non-DSI bridge convertor would require a bridge
> > driver that would communicate the DSI controller for bridge
> > functionalities.
> > 
> > So, add support for bridge functionalities in Allwinner DSI
> > controller.
> 
> See a few comments below.
> 
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > ---
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
> >  2 files changed, 49 insertions(+), 17 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > index 0960b96b62cc..64d74313b842 100644
> > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> >  	if (!IS_ERR(dsi->panel))
> >  		drm_panel_prepare(dsi->panel);
> >  
> > +	if (!IS_ERR(dsi->bridge))
> > +		drm_bridge_pre_enable(dsi->bridge);
> > +
> >  	/*
> >  	 * FIXME: This should be moved after the switch to HS mode.
> >  	 *
> > @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> >  	if (!IS_ERR(dsi->panel))
> >  		drm_panel_enable(dsi->panel);
> >  
> > +	if (!IS_ERR(dsi->bridge))
> > +		drm_bridge_enable(dsi->bridge);
> > +
> >  	sun6i_dsi_start(dsi, DSI_START_HSC);
> >  
> >  	udelay(1000);
> > @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
> >  	if (!IS_ERR(dsi->panel)) {
> >  		drm_panel_disable(dsi->panel);
> >  		drm_panel_unprepare(dsi->panel);
> > +	} else if (!IS_ERR(dsi->bridge)) {
> > +		drm_bridge_disable(dsi->bridge);
> > +		drm_bridge_post_disable(dsi->bridge);
> >  	}
> >  
> >  	phy_power_off(dsi->dphy);
> > @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
> >  	struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> >  
> >  	dsi->device = device;
> > -	dsi->panel = of_drm_find_panel(device->dev.of_node);
> > -	if (IS_ERR(dsi->panel))
> > -		return PTR_ERR(dsi->panel);
> >  
> > -	dev_info(host->dev, "Attached device %s\n", device->name);
> > +	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> > +	if (!dsi->bridge) {
> 
> You are using IS_ERR to check that the bridge is alive in the changes
> above, but switch to checking that it's non-NULL at this point.
> 
> Are both guaranteed to be interchangeable?

They aren't. Any ERR_PTR will be !NULL

> > +		dsi->panel = of_drm_find_panel(device->dev.of_node);
> > +		if (IS_ERR(dsi->panel))
> > +			return PTR_ERR(dsi->panel);
> > +	}
> 
> You should probably use drm_of_find_panel_or_bridge instead of
> duplicating the logic here.

Or we can even use the drm_panel_bridge_add to simplify things.

Maxime
  

Hi,

On Fri, 2019-03-15 at 14:45 +0100, Maxime Ripard wrote:
> On Fri, Mar 15, 2019 at 02:32:55PM +0100, Paul Kocialkowski wrote:
> > Hi,
> > 
> > On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
> > > Some display panels would come up with a non-DSI output which
> > > can have an option to connect DSI interface by means of bridge
> > > convertor.
> > > 
> > > This DSI to non-DSI bridge convertor would require a bridge
> > > driver that would communicate the DSI controller for bridge
> > > functionalities.
> > > 
> > > So, add support for bridge functionalities in Allwinner DSI
> > > controller.
> > 
> > See a few comments below.
> > 
> > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > > ---
> > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
> > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
> > >  2 files changed, 49 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > index 0960b96b62cc..64d74313b842 100644
> > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > >  	if (!IS_ERR(dsi->panel))
> > >  		drm_panel_prepare(dsi->panel);
> > >  
> > > +	if (!IS_ERR(dsi->bridge))
> > > +		drm_bridge_pre_enable(dsi->bridge);
> > > +
> > >  	/*
> > >  	 * FIXME: This should be moved after the switch to HS mode.
> > >  	 *
> > > @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> > >  	if (!IS_ERR(dsi->panel))
> > >  		drm_panel_enable(dsi->panel);
> > >  
> > > +	if (!IS_ERR(dsi->bridge))
> > > +		drm_bridge_enable(dsi->bridge);
> > > +
> > >  	sun6i_dsi_start(dsi, DSI_START_HSC);
> > >  
> > >  	udelay(1000);
> > > @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
> > >  	if (!IS_ERR(dsi->panel)) {
> > >  		drm_panel_disable(dsi->panel);
> > >  		drm_panel_unprepare(dsi->panel);
> > > +	} else if (!IS_ERR(dsi->bridge)) {
> > > +		drm_bridge_disable(dsi->bridge);
> > > +		drm_bridge_post_disable(dsi->bridge);
> > >  	}
> > >  
> > >  	phy_power_off(dsi->dphy);
> > > @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
> > >  	struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> > >  
> > >  	dsi->device = device;
> > > -	dsi->panel = of_drm_find_panel(device->dev.of_node);
> > > -	if (IS_ERR(dsi->panel))
> > > -		return PTR_ERR(dsi->panel);
> > >  
> > > -	dev_info(host->dev, "Attached device %s\n", device->name);
> > > +	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> > > +	if (!dsi->bridge) {
> > 
> > You are using IS_ERR to check that the bridge is alive in the changes
> > above, but switch to checking that it's non-NULL at this point.
> > 
> > Are both guaranteed to be interchangeable?
> 
> They aren't. Any ERR_PTR will be !NULL
> 
> > > +		dsi->panel = of_drm_find_panel(device->dev.of_node);
> > > +		if (IS_ERR(dsi->panel))
> > > +			return PTR_ERR(dsi->panel);
> > > +	}
> > 
> > You should probably use drm_of_find_panel_or_bridge instead of
> > duplicating the logic here.
> 
> Or we can even use the drm_panel_bridge_add to simplify things.

Indeed, I was just looking at that and it seems to be specifically
tailored for this use case.

Cheers,

Paul
  

Hi, Jagan,

On 3/15/19 4:45 PM, Maxime Ripard wrote:
> On Fri, Mar 15, 2019 at 02:32:55PM +0100, Paul Kocialkowski wrote:
>> Hi,
>>
>> On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
>>> Some display panels would come up with a non-DSI output which
>>> can have an option to connect DSI interface by means of bridge
>>> convertor.
>>>
>>> This DSI to non-DSI bridge convertor would require a bridge
>>> driver that would communicate the DSI controller for bridge
>>> functionalities.
>>>
>>> So, add support for bridge functionalities in Allwinner DSI
>>> controller.
>> See a few comments below.
>>
>>> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
>>> ---
>>>   drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
>>>   drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
>>>   2 files changed, 49 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>> index 0960b96b62cc..64d74313b842 100644
>>> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>> @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>>>   	if (!IS_ERR(dsi->panel))
>>>   		drm_panel_prepare(dsi->panel);
>>>   
>>> +	if (!IS_ERR(dsi->bridge))
>>> +		drm_bridge_pre_enable(dsi->bridge);
>>> +
>>>   	/*
>>>   	 * FIXME: This should be moved after the switch to HS mode.
>>>   	 *
>>> @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
>>>   	if (!IS_ERR(dsi->panel))
>>>   		drm_panel_enable(dsi->panel);
>>>   
>>> +	if (!IS_ERR(dsi->bridge))
>>> +		drm_bridge_enable(dsi->bridge);
>>> +
>>>   	sun6i_dsi_start(dsi, DSI_START_HSC);
>>>   
>>>   	udelay(1000);
>>> @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
>>>   	if (!IS_ERR(dsi->panel)) {
>>>   		drm_panel_disable(dsi->panel);
>>>   		drm_panel_unprepare(dsi->panel);
>>> +	} else if (!IS_ERR(dsi->bridge)) {
>>> +		drm_bridge_disable(dsi->bridge);
>>> +		drm_bridge_post_disable(dsi->bridge);
>>>   	}
>>>   
>>>   	phy_power_off(dsi->dphy);
>>> @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
>>>   	struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
>>>   
>>>   	dsi->device = device;
>>> -	dsi->panel = of_drm_find_panel(device->dev.of_node);
>>> -	if (IS_ERR(dsi->panel))
>>> -		return PTR_ERR(dsi->panel);
>>>   
>>> -	dev_info(host->dev, "Attached device %s\n", device->name);
>>> +	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
>>> +	if (!dsi->bridge) {
>> You are using IS_ERR to check that the bridge is alive in the changes
>> above, but switch to checking that it's non-NULL at this point.
>>
>> Are both guaranteed to be interchangeable?
> They aren't. Any ERR_PTR will be !NULL
>
>>> +		dsi->panel = of_drm_find_panel(device->dev.of_node);
>>> +		if (IS_ERR(dsi->panel))
>>> +			return PTR_ERR(dsi->panel);
>>> +	}
>> You should probably use drm_of_find_panel_or_bridge instead of
>> duplicating the logic here.
> Or we can even use the drm_panel_bridge_add to simplify things.

this approach is implemented by E.Anholt in VC4 dsi driver and it looks 
nice.

>
> Maxime
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
  

Hi Paul and Maxime,

On Fri, Mar 15, 2019 at 7:03 PM Paul Kocialkowski
<paul.kocialkowski@bootlin.com> wrote:
>
> Hi,
>
> On Fri, 2019-03-15 at 18:38 +0530, Jagan Teki wrote:
> > Some display panels would come up with a non-DSI output which
> > can have an option to connect DSI interface by means of bridge
> > convertor.
> >
> > This DSI to non-DSI bridge convertor would require a bridge
> > driver that would communicate the DSI controller for bridge
> > functionalities.
> >
> > So, add support for bridge functionalities in Allwinner DSI
> > controller.
>
> See a few comments below.
>
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > ---
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 65 +++++++++++++++++++-------
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h |  1 +
> >  2 files changed, 49 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > index 0960b96b62cc..64d74313b842 100644
> > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > @@ -781,6 +781,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> >       if (!IS_ERR(dsi->panel))
> >               drm_panel_prepare(dsi->panel);
> >
> > +     if (!IS_ERR(dsi->bridge))
> > +             drm_bridge_pre_enable(dsi->bridge);
> > +
> >       /*
> >        * FIXME: This should be moved after the switch to HS mode.
> >        *
> > @@ -796,6 +799,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> >       if (!IS_ERR(dsi->panel))
> >               drm_panel_enable(dsi->panel);
> >
> > +     if (!IS_ERR(dsi->bridge))
> > +             drm_bridge_enable(dsi->bridge);
> > +
> >       sun6i_dsi_start(dsi, DSI_START_HSC);
> >
> >       udelay(1000);
> > @@ -812,6 +818,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
> >       if (!IS_ERR(dsi->panel)) {
> >               drm_panel_disable(dsi->panel);
> >               drm_panel_unprepare(dsi->panel);
> > +     } else if (!IS_ERR(dsi->bridge)) {
> > +             drm_bridge_disable(dsi->bridge);
> > +             drm_bridge_post_disable(dsi->bridge);
> >       }
> >
> >       phy_power_off(dsi->dphy);
> > @@ -973,11 +982,16 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
> >       struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> >
> >       dsi->device = device;
> > -     dsi->panel = of_drm_find_panel(device->dev.of_node);
> > -     if (IS_ERR(dsi->panel))
> > -             return PTR_ERR(dsi->panel);
> >
> > -     dev_info(host->dev, "Attached device %s\n", device->name);
> > +     dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> > +     if (!dsi->bridge) {
>
> You are using IS_ERR to check that the bridge is alive in the changes
> above, but switch to checking that it's non-NULL at this point.
>
> Are both guaranteed to be interchangeable?
>
> > +             dsi->panel = of_drm_find_panel(device->dev.of_node);
> > +             if (IS_ERR(dsi->panel))
> > +                     return PTR_ERR(dsi->panel);
> > +     }
>
> You should probably use drm_of_find_panel_or_bridge instead of
> duplicating the logic here.

True, In-fact I did try this API. but pipeline were unable to bound.
Usually the panel and bridge were attached first and then the pipeline
bound would start from front-end (in A33) But in my below cases I have
seen only panel or bridge attached but no pipeline bound at all.

And I'm using drm_of_find_panel_or_bridge(host->dev->of_node, 1, 0,
&dsi->panel, &dsi->bridge); in dsi attach API.

Case-1, panel:

&dsi {
    vcc-dsi-supply = <&reg_dcdc1>;        /* VCC3V3-DSI */
    status = "okay";

    ports {
        dsi_out: port@1 {
            reg = <1>;

            dsi_out_panel: endpoint {
                remote-endpoint = <&panel_out_dsi>;
            };
        };
    };

    panel@0 {
        compatible = "bananapi,s070wv20-ct16-icn6211";
        reg = <0>;
        enable-gpios = <&pio 1 7 GPIO_ACTIVE_HIGH>; /* LCD-PWR-EN: PB7 */
        reset-gpios = <&r_pio 0 5 GPIO_ACTIVE_HIGH>; /* LCD-RST: PL5 */
        backlight = <&backlight>;

        port {
            panel_out_dsi: endpoint {
                remote-endpoint = <&dsi_out_panel>;
            };
        };
    };
};

Case-2, bridge:

    panel {
        compatible = "bananapi,s070wv20-ct16", "simple-panel";
        enable-gpios = <&pio 1 7 GPIO_ACTIVE_HIGH>; /* LCD-PWR-EN: PB7 */
        backlight = <&backlight>;

        port {

            panel_out_bridge: endpoint {
                remote-endpoint = <&bridge_out_panel>;
            };
        };
    };

&dsi {
    vcc-dsi-supply = <&reg_dcdc1>;        /* VCC-DSI */
    status = "okay";

    ports {
        dsi_out: port@1 {
            reg = <1>;

            dsi_out_bridge: endpoint {
                remote-endpoint = <&bridge_out_dsi>;
            };
        };
    };

    bridge@0 {
        reg = <0>;
        compatible = "bananapi,icn6211", "chipone,icn6211";
        reset-gpios = <&r_pio 0 5 GPIO_ACTIVE_HIGH>; /* LCD-RST: PL5 */
        #address-cells = <1>;
        #size-cells = <0>;

        ports {
            #address-cells = <1>;
            #size-cells = <0>;

            bridge_in: port@0 {
                reg = <0>;

                bridge_out_dsi: endpoint {
                    remote-endpoint = <&dsi_out_bridge>;
                };
            };

            bridge_out: port@1 {
                reg = <1>;

                bridge_out_panel: endpoint {
                    remote-endpoint = <&panel_out_bridge>;
                };
            };
        };
    };
};

I think, I'm sure about the pipeline connections as per my
understanding. but something loosely missed here or in the code.
Please do let me know for any suggestions.

Jagan.