[PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Marek Vasut]

The OnSemi FIN3385 Parallel-to-LVDS encoder has a dedicated input line to
select input pixel data sampling edge. Add DT property "pixelclk-active",
same as the one used by display timings, and configure bus flags based on
this DT property.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Antonio Borneo <antonio.borneo@st.com>
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Philippe Cornu <philippe.cornu@st.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Yannick Fertre <yannick.fertre@st.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: dri-devel@lists.freedesktop.org
---
V2: - Limit the pixelclk-active to encoders only
    - Update DT binding document
---
 .../bindings/display/bridge/lvds-codec.yaml   |  7 +++
 drivers/gpu/drm/bridge/lvds-codec.c           | 52 +++++++++++++------
 2 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
index e5e3c72630cf..399a6528780a 100644
--- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
@@ -74,6 +74,13 @@ properties:
 
     additionalProperties: false
 
+  pixelclk-active:
+    description: |
+      Data sampling on rising or falling edge.
+      Use 0 to sample pixel data on rising edge and
+      Use 1 to sample pixel data on falling edge and
+    enum: [0, 1]
+
   powerdown-gpios:
     description:
       The GPIO used to control the power down line of this device.
diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
index dcf579a4cf83..cab81ccd895d 100644
--- a/drivers/gpu/drm/bridge/lvds-codec.c
+++ b/drivers/gpu/drm/bridge/lvds-codec.c
@@ -15,13 +15,18 @@
 #include <drm/drm_bridge.h>
 #include <drm/drm_panel.h>
 
+struct lvds_codec_data {
+	u32 connector_type;
+	bool is_encoder;
+};
+
 struct lvds_codec {
 	struct device *dev;
 	struct drm_bridge bridge;
 	struct drm_bridge *panel_bridge;
+	struct drm_bridge_timings timings;
 	struct regulator *vcc;
 	struct gpio_desc *powerdown_gpio;
-	u32 connector_type;
 };
 
 static inline struct lvds_codec *to_lvds_codec(struct drm_bridge *bridge)
@@ -76,17 +81,20 @@ static const struct drm_bridge_funcs funcs = {
 
 static int lvds_codec_probe(struct platform_device *pdev)
 {
+	const struct lvds_codec_data *data;
 	struct device *dev = &pdev->dev;
 	struct device_node *panel_node;
 	struct drm_panel *panel;
 	struct lvds_codec *lvds_codec;
+	u32 val;
 
 	lvds_codec = devm_kzalloc(dev, sizeof(*lvds_codec), GFP_KERNEL);
 	if (!lvds_codec)
 		return -ENOMEM;
 
+	data = of_device_get_match_data(dev);
+
 	lvds_codec->dev = &pdev->dev;
-	lvds_codec->connector_type = (uintptr_t)of_device_get_match_data(dev);
 
 	lvds_codec->vcc = devm_regulator_get(lvds_codec->dev, "power");
 	if (IS_ERR(lvds_codec->vcc))
@@ -115,10 +123,22 @@ static int lvds_codec_probe(struct platform_device *pdev)
 
 	lvds_codec->panel_bridge =
 		devm_drm_panel_bridge_add_typed(dev, panel,
-						lvds_codec->connector_type);
+						data->connector_type);
 	if (IS_ERR(lvds_codec->panel_bridge))
 		return PTR_ERR(lvds_codec->panel_bridge);
 
+	/*
+	 * Encoder might sample data on different clock edge than the display,
+	 * for example OnSemi FIN3385 has a dedicated strapping pin to select
+	 * the sampling edge.
+	 */
+	if (data->is_encoder &&
+	    !of_property_read_u32(dev->of_node, "pixelclk-active", &val)) {
+		lvds_codec->timings.input_bus_flags = val ?
+			DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE :
+			DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE;
+	}
+
 	/*
 	 * The panel_bridge bridge is attached to the panel's of_node,
 	 * but we need a bridge attached to our of_node for our user
@@ -126,6 +146,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
 	 */
 	lvds_codec->bridge.of_node = dev->of_node;
 	lvds_codec->bridge.funcs = &funcs;
+	lvds_codec->bridge.timings = &lvds_codec->timings;
 	drm_bridge_add(&lvds_codec->bridge);
 
 	platform_set_drvdata(pdev, lvds_codec);
@@ -142,19 +163,20 @@ static int lvds_codec_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static const struct lvds_codec_data decoder_data = {
+	.connector_type = DRM_MODE_CONNECTOR_DPI,
+	.is_encoder = false,
+};
+
+static const struct lvds_codec_data encoder_data = {
+	.connector_type = DRM_MODE_CONNECTOR_LVDS,
+	.is_encoder = true,
+};
+
 static const struct of_device_id lvds_codec_match[] = {
-	{
-		.compatible = "lvds-decoder",
-		.data = (void *)DRM_MODE_CONNECTOR_DPI,
-	},
-	{
-		.compatible = "lvds-encoder",
-		.data = (void *)DRM_MODE_CONNECTOR_LVDS,
-	},
-	{
-		.compatible = "thine,thc63lvdm83d",
-		.data = (void *)DRM_MODE_CONNECTOR_LVDS,
-	},
+	{ .compatible = "lvds-decoder", .data = &decoder_data, },
+	{ .compatible = "lvds-encoder", .data = &encoder_data, },
+	{ .compatible = "thine,thc63lvdm83d", .data = &encoder_data, },
 	{},
 };
 MODULE_DEVICE_TABLE(of, lvds_codec_match);
-- 
2.29.2


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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Marek Vasut]

On 12/24/20 7:18 AM, Marek Vasut wrote:
> The OnSemi FIN3385 Parallel-to-LVDS encoder has a dedicated input line to
> select input pixel data sampling edge. Add DT property "pixelclk-active",
> same as the one used by display timings, and configure bus flags based on
> this DT property.

Bump ?

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Marek Vasut]

On 1/24/21 6:04 PM, Marek Vasut wrote:
> On 12/24/20 7:18 AM, Marek Vasut wrote:
>> The OnSemi FIN3385 Parallel-to-LVDS encoder has a dedicated input line to
>> select input pixel data sampling edge. Add DT property "pixelclk-active",
>> same as the one used by display timings, and configure bus flags based on
>> this DT property.
> 
> Bump ?

Any news on this patch ?

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Laurent Pinchart]

Hi Marek,

All my apologies for the awfully delayed review, and thank you for
pinging me.

On Thu, Dec 24, 2020 at 07:18:32AM +0100, Marek Vasut wrote:
> The OnSemi FIN3385 Parallel-to-LVDS encoder has a dedicated input line to
> select input pixel data sampling edge. Add DT property "pixelclk-active",
> same as the one used by display timings, and configure bus flags based on
> this DT property.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Alexandre Torgue <alexandre.torgue@st.com>
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: Antonio Borneo <antonio.borneo@st.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
> Cc: Biju Das <biju.das.jz@bp.renesas.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> Cc: Philippe Cornu <philippe.cornu@st.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: Vincent Abriou <vincent.abriou@st.com>
> Cc: Yannick Fertre <yannick.fertre@st.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-stm32@st-md-mailman.stormreply.com
> To: dri-devel@lists.freedesktop.org
> ---
> V2: - Limit the pixelclk-active to encoders only
>     - Update DT binding document
> ---
>  .../bindings/display/bridge/lvds-codec.yaml   |  7 +++
>  drivers/gpu/drm/bridge/lvds-codec.c           | 52 +++++++++++++------
>  2 files changed, 44 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> index e5e3c72630cf..399a6528780a 100644
> --- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> @@ -74,6 +74,13 @@ properties:
>  
>      additionalProperties: false
>  
> +  pixelclk-active:
> +    description: |
> +      Data sampling on rising or falling edge.
> +      Use 0 to sample pixel data on rising edge and
> +      Use 1 to sample pixel data on falling edge and
> +    enum: [0, 1]

The idea is good, but instead of adding a custom property, how about
reusing the pclk-sample property defined in
../../media/video-interfaces.yaml ?

The property is only valid for encoders, so I would at least mention
that in the description, or, better, handle this based on the compatible
string to allow validation.

> +
>    powerdown-gpios:
>      description:
>        The GPIO used to control the power down line of this device.
> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> index dcf579a4cf83..cab81ccd895d 100644
> --- a/drivers/gpu/drm/bridge/lvds-codec.c
> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> @@ -15,13 +15,18 @@
>  #include <drm/drm_bridge.h>
>  #include <drm/drm_panel.h>
>  
> +struct lvds_codec_data {
> +	u32 connector_type;
> +	bool is_encoder;
> +};
> +
>  struct lvds_codec {
>  	struct device *dev;
>  	struct drm_bridge bridge;
>  	struct drm_bridge *panel_bridge;
> +	struct drm_bridge_timings timings;
>  	struct regulator *vcc;
>  	struct gpio_desc *powerdown_gpio;
> -	u32 connector_type;
>  };
>  
>  static inline struct lvds_codec *to_lvds_codec(struct drm_bridge *bridge)
> @@ -76,17 +81,20 @@ static const struct drm_bridge_funcs funcs = {
>  
>  static int lvds_codec_probe(struct platform_device *pdev)
>  {
> +	const struct lvds_codec_data *data;
>  	struct device *dev = &pdev->dev;
>  	struct device_node *panel_node;
>  	struct drm_panel *panel;
>  	struct lvds_codec *lvds_codec;
> +	u32 val;
>  
>  	lvds_codec = devm_kzalloc(dev, sizeof(*lvds_codec), GFP_KERNEL);
>  	if (!lvds_codec)
>  		return -ENOMEM;
>  
> +	data = of_device_get_match_data(dev);
> +
>  	lvds_codec->dev = &pdev->dev;
> -	lvds_codec->connector_type = (uintptr_t)of_device_get_match_data(dev);
>  
>  	lvds_codec->vcc = devm_regulator_get(lvds_codec->dev, "power");
>  	if (IS_ERR(lvds_codec->vcc))
> @@ -115,10 +123,22 @@ static int lvds_codec_probe(struct platform_device *pdev)
>  
>  	lvds_codec->panel_bridge =
>  		devm_drm_panel_bridge_add_typed(dev, panel,
> -						lvds_codec->connector_type);
> +						data->connector_type);
>  	if (IS_ERR(lvds_codec->panel_bridge))
>  		return PTR_ERR(lvds_codec->panel_bridge);
>  
> +	/*
> +	 * Encoder might sample data on different clock edge than the display,
> +	 * for example OnSemi FIN3385 has a dedicated strapping pin to select
> +	 * the sampling edge.
> +	 */
> +	if (data->is_encoder &&
> +	    !of_property_read_u32(dev->of_node, "pixelclk-active", &val)) {
> +		lvds_codec->timings.input_bus_flags = val ?
> +			DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE :
> +			DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE;
> +	}
> +
>  	/*
>  	 * The panel_bridge bridge is attached to the panel's of_node,
>  	 * but we need a bridge attached to our of_node for our user
> @@ -126,6 +146,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
>  	 */
>  	lvds_codec->bridge.of_node = dev->of_node;
>  	lvds_codec->bridge.funcs = &funcs;
> +	lvds_codec->bridge.timings = &lvds_codec->timings;
>  	drm_bridge_add(&lvds_codec->bridge);
>  
>  	platform_set_drvdata(pdev, lvds_codec);
> @@ -142,19 +163,20 @@ static int lvds_codec_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static const struct lvds_codec_data decoder_data = {
> +	.connector_type = DRM_MODE_CONNECTOR_DPI,
> +	.is_encoder = false,

The two fields are a bit redundant, as the decoder is always
LVDS-to-DPI, and the encoder DPI-to-LVDS. I don't mind too much, but
maybe we could drop the connector_type field, and derive the connector
type from is_encoder ?

One may then say that we could drop the lvds_codec_data structure as it
contains a single field, but I foresee a need to have device-specific
timings at some point, so I think it's a good addition.

The patch otherwise looks good.

> +};
> +
> +static const struct lvds_codec_data encoder_data = {
> +	.connector_type = DRM_MODE_CONNECTOR_LVDS,
> +	.is_encoder = true,
> +};
> +
>  static const struct of_device_id lvds_codec_match[] = {
> -	{
> -		.compatible = "lvds-decoder",
> -		.data = (void *)DRM_MODE_CONNECTOR_DPI,
> -	},
> -	{
> -		.compatible = "lvds-encoder",
> -		.data = (void *)DRM_MODE_CONNECTOR_LVDS,
> -	},
> -	{
> -		.compatible = "thine,thc63lvdm83d",
> -		.data = (void *)DRM_MODE_CONNECTOR_LVDS,
> -	},
> +	{ .compatible = "lvds-decoder", .data = &decoder_data, },
> +	{ .compatible = "lvds-encoder", .data = &encoder_data, },
> +	{ .compatible = "thine,thc63lvdm83d", .data = &encoder_data, },
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, lvds_codec_match);

-- 
Regards,

Laurent Pinchart

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Marek Vasut]

On 3/22/21 2:14 AM, Laurent Pinchart wrote:
> Hi Marek,

Hi,

[...]

>> diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>> index e5e3c72630cf..399a6528780a 100644
>> --- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>> +++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>> @@ -74,6 +74,13 @@ properties:
>>   
>>       additionalProperties: false
>>   
>> +  pixelclk-active:
>> +    description: |
>> +      Data sampling on rising or falling edge.
>> +      Use 0 to sample pixel data on rising edge and
>> +      Use 1 to sample pixel data on falling edge and
>> +    enum: [0, 1]
> 
> The idea is good, but instead of adding a custom property, how about
> reusing the pclk-sample property defined in
> ../../media/video-interfaces.yaml ?

Repeating myself from V1 discussion ... Either is fine by me, but I 
think pixelclk-active, which comes from panel-timings.yaml is closer to 
the video than multimedia bindings.

> The property is only valid for encoders, so I would at least mention
> that in the description, or, better, handle this based on the compatible
> string to allow validation.

How does that work in the Yaml file ?

>> +
>>     powerdown-gpios:
>>       description:
>>         The GPIO used to control the power down line of this device.
>> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
>> index dcf579a4cf83..cab81ccd895d 100644
>> --- a/drivers/gpu/drm/bridge/lvds-codec.c
>> +++ b/drivers/gpu/drm/bridge/lvds-codec.c

[...]

>> @@ -126,6 +146,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
>>   	 */
>>   	lvds_codec->bridge.of_node = dev->of_node;
>>   	lvds_codec->bridge.funcs = &funcs;
>> +	lvds_codec->bridge.timings = &lvds_codec->timings;
>>   	drm_bridge_add(&lvds_codec->bridge);
>>   
>>   	platform_set_drvdata(pdev, lvds_codec);
>> @@ -142,19 +163,20 @@ static int lvds_codec_remove(struct platform_device *pdev)
>>   	return 0;
>>   }
>>   
>> +static const struct lvds_codec_data decoder_data = {
>> +	.connector_type = DRM_MODE_CONNECTOR_DPI,
>> +	.is_encoder = false,
> 
> The two fields are a bit redundant, as the decoder is always
> LVDS-to-DPI, and the encoder DPI-to-LVDS. I don't mind too much, but
> maybe we could drop the connector_type field, and derive the connector
> type from is_encoder ?

Or the other way around instead ? That is, if the connector_type is 
LVDS, then it is encoder , otherwise its decoder ?

> One may then say that we could drop the lvds_codec_data structure as it
> contains a single field, but I foresee a need to have device-specific
> timings at some point, so I think it's a good addition.

[...]

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Laurent Pinchart]

Hi Marek,

(CC'ing Ron and the DT mailing list for the DT discussion)

On Mon, Mar 22, 2021 at 11:29:04AM +0100, Marek Vasut wrote:
> On 3/22/21 2:14 AM, Laurent Pinchart wrote:
> > Hi Marek,
> 
> Hi,
> 
> [...]
> 
> >> diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> >> index e5e3c72630cf..399a6528780a 100644
> >> --- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> >> +++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> >> @@ -74,6 +74,13 @@ properties:
> >>   
> >>       additionalProperties: false
> >>   
> >> +  pixelclk-active:
> >> +    description: |
> >> +      Data sampling on rising or falling edge.
> >> +      Use 0 to sample pixel data on rising edge and
> >> +      Use 1 to sample pixel data on falling edge and
> >> +    enum: [0, 1]
> > 
> > The idea is good, but instead of adding a custom property, how about
> > reusing the pclk-sample property defined in
> > ../../media/video-interfaces.yaml ?
> 
> Repeating myself from V1 discussion ... Either is fine by me, but I 
> think pixelclk-active, which comes from panel-timings.yaml is closer to 
> the video than multimedia bindings.

That's a good point. The part that bothers me a bit is that it would be
nice to define the property in a single YAML schema, referenced by
individual bindings. video-interfaces.yaml is there for that purpose. We
could do something similar on the display side, or consider the
pixelclk-active usage in panel-timings.yaml an exception that we can't
switch to video-interfaces.yaml as backward compatibility must be
preserved.

I don't have a too strong preference, whatever Rob prefers would be fine
with me.

> > The property is only valid for encoders, so I would at least mention
> > that in the description, or, better, handle this based on the compatible
> > string to allow validation.
> 
> How does that work in the Yaml file ?

Something along the lines of

if:
  not:
    properties:
      compatible:
        contains:
          const: lvds-encoder
then:
  properties:
    pixelclk-active: false

My YAML schema foo is a bit rusty though, I apologize if this doesn't
work as-is. There are lots of similar examples in DT bindings that
should hopefully be right :-)

> >> +
> >>     powerdown-gpios:
> >>       description:
> >>         The GPIO used to control the power down line of this device.
> >> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> >> index dcf579a4cf83..cab81ccd895d 100644
> >> --- a/drivers/gpu/drm/bridge/lvds-codec.c
> >> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> 
> [...]
> 
> >> @@ -126,6 +146,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
> >>   	 */
> >>   	lvds_codec->bridge.of_node = dev->of_node;
> >>   	lvds_codec->bridge.funcs = &funcs;
> >> +	lvds_codec->bridge.timings = &lvds_codec->timings;
> >>   	drm_bridge_add(&lvds_codec->bridge);
> >>   
> >>   	platform_set_drvdata(pdev, lvds_codec);
> >> @@ -142,19 +163,20 @@ static int lvds_codec_remove(struct platform_device *pdev)
> >>   	return 0;
> >>   }
> >>   
> >> +static const struct lvds_codec_data decoder_data = {
> >> +	.connector_type = DRM_MODE_CONNECTOR_DPI,
> >> +	.is_encoder = false,
> > 
> > The two fields are a bit redundant, as the decoder is always
> > LVDS-to-DPI, and the encoder DPI-to-LVDS. I don't mind too much, but
> > maybe we could drop the connector_type field, and derive the connector
> > type from is_encoder ?
> 
> Or the other way around instead ? That is, if the connector_type is 
> LVDS, then it is encoder , otherwise its decoder ?

Either way works for me.

> > One may then say that we could drop the lvds_codec_data structure as it
> > contains a single field, but I foresee a need to have device-specific
> > timings at some point, so I think it's a good addition.
> 
> [...]

-- 
Regards,

Laurent Pinchart

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Marek Vasut]

On 3/22/21 11:29 AM, Marek Vasut wrote:
> On 3/22/21 2:14 AM, Laurent Pinchart wrote:
>> Hi Marek,
> 
> Hi,
> 
> [...]
> 
>>> diff --git 
>>> a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml 
>>> b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>>> index e5e3c72630cf..399a6528780a 100644
>>> --- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>>> +++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
>>> @@ -74,6 +74,13 @@ properties:
>>>       additionalProperties: false
>>> +  pixelclk-active:
>>> +    description: |
>>> +      Data sampling on rising or falling edge.
>>> +      Use 0 to sample pixel data on rising edge and
>>> +      Use 1 to sample pixel data on falling edge and
>>> +    enum: [0, 1]
>>
>> The idea is good, but instead of adding a custom property, how about
>> reusing the pclk-sample property defined in
>> ../../media/video-interfaces.yaml ?
> 
> Repeating myself from V1 discussion ... Either is fine by me, but I 
> think pixelclk-active, which comes from panel-timings.yaml is closer to 
> the video than multimedia bindings.

Was there ever any reply from Rob on this ?

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Re: [PATCH V2] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Laurent Pinchart]

Hi Rob,

There's a question for you below.

On Mon, Mar 22, 2021 at 12:37:47PM +0200, Laurent Pinchart wrote:
> Hi Marek,
> 
> (CC'ing Ron and the DT mailing list for the DT discussion)
> 
> On Mon, Mar 22, 2021 at 11:29:04AM +0100, Marek Vasut wrote:
> > On 3/22/21 2:14 AM, Laurent Pinchart wrote:
> > > Hi Marek,
> > 
> > Hi,
> > 
> > [...]
> > 
> > >> diff --git a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> > >> index e5e3c72630cf..399a6528780a 100644
> > >> --- a/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> > >> +++ b/Documentation/devicetree/bindings/display/bridge/lvds-codec.yaml
> > >> @@ -74,6 +74,13 @@ properties:
> > >>   
> > >>       additionalProperties: false
> > >>   
> > >> +  pixelclk-active:
> > >> +    description: |
> > >> +      Data sampling on rising or falling edge.
> > >> +      Use 0 to sample pixel data on rising edge and
> > >> +      Use 1 to sample pixel data on falling edge and
> > >> +    enum: [0, 1]
> > > 
> > > The idea is good, but instead of adding a custom property, how about
> > > reusing the pclk-sample property defined in
> > > ../../media/video-interfaces.yaml ?
> > 
> > Repeating myself from V1 discussion ... Either is fine by me, but I 
> > think pixelclk-active, which comes from panel-timings.yaml is closer to 
> > the video than multimedia bindings.
> 
> That's a good point. The part that bothers me a bit is that it would be
> nice to define the property in a single YAML schema, referenced by
> individual bindings. video-interfaces.yaml is there for that purpose. We
> could do something similar on the display side, or consider the
> pixelclk-active usage in panel-timings.yaml an exception that we can't
> switch to video-interfaces.yaml as backward compatibility must be
> preserved.
> 
> I don't have a too strong preference, whatever Rob prefers would be fine
> with me.
> 
> > > The property is only valid for encoders, so I would at least mention
> > > that in the description, or, better, handle this based on the compatible
> > > string to allow validation.
> > 
> > How does that work in the Yaml file ?
> 
> Something along the lines of
> 
> if:
>   not:
>     properties:
>       compatible:
>         contains:
>           const: lvds-encoder
> then:
>   properties:
>     pixelclk-active: false
> 
> My YAML schema foo is a bit rusty though, I apologize if this doesn't
> work as-is. There are lots of similar examples in DT bindings that
> should hopefully be right :-)
> 
> > >> +
> > >>     powerdown-gpios:
> > >>       description:
> > >>         The GPIO used to control the power down line of this device.
> > >> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> > >> index dcf579a4cf83..cab81ccd895d 100644
> > >> --- a/drivers/gpu/drm/bridge/lvds-codec.c
> > >> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> > 
> > [...]
> > 
> > >> @@ -126,6 +146,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
> > >>   	 */
> > >>   	lvds_codec->bridge.of_node = dev->of_node;
> > >>   	lvds_codec->bridge.funcs = &funcs;
> > >> +	lvds_codec->bridge.timings = &lvds_codec->timings;
> > >>   	drm_bridge_add(&lvds_codec->bridge);
> > >>   
> > >>   	platform_set_drvdata(pdev, lvds_codec);
> > >> @@ -142,19 +163,20 @@ static int lvds_codec_remove(struct platform_device *pdev)
> > >>   	return 0;
> > >>   }
> > >>   
> > >> +static const struct lvds_codec_data decoder_data = {
> > >> +	.connector_type = DRM_MODE_CONNECTOR_DPI,
> > >> +	.is_encoder = false,
> > > 
> > > The two fields are a bit redundant, as the decoder is always
> > > LVDS-to-DPI, and the encoder DPI-to-LVDS. I don't mind too much, but
> > > maybe we could drop the connector_type field, and derive the connector
> > > type from is_encoder ?
> > 
> > Or the other way around instead ? That is, if the connector_type is 
> > LVDS, then it is encoder , otherwise its decoder ?
> 
> Either way works for me.
> 
> > > One may then say that we could drop the lvds_codec_data structure as it
> > > contains a single field, but I foresee a need to have device-specific
> > > timings at some point, so I think it's a good addition.
> > 
> > [...]

-- 
Regards,

Laurent Pinchart

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