[v2,1/2] dt-bindings: drm/bridge: Add no-hpd property

  From: Rahul T R <r-ravikumar@ti.com>

The mhdp bridge can work without its HPD pin hooked up to the connector,
but the current bridge driver throws an error when hpd line is not
connected to the connector. For such cases, we need an indication for
no-hpd, using which we can bypass the hpd detection and instead use the
auxiliary channels connected to the DP connector to confirm the
connection.
So add no-hpd property to the bindings, to disable hpd when not
connected or unusable.

Signed-off-by: Rahul T R <r-ravikumar@ti.com>
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
---
 .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6 ++++++
 1 file changed, 6 insertions(+)
  

Hi Jayesh,

Thank you for the patch.

On Wed, Apr 05, 2023 at 07:54:39PM +0530, Jayesh Choudhary wrote:
> From: Rahul T R <r-ravikumar@ti.com>
> 
> The mhdp bridge can work without its HPD pin hooked up to the connector,
> but the current bridge driver throws an error when hpd line is not
> connected to the connector. For such cases, we need an indication for
> no-hpd, using which we can bypass the hpd detection and instead use the
> auxiliary channels connected to the DP connector to confirm the
> connection.
> So add no-hpd property to the bindings, to disable hpd when not
> connected or unusable.
> 
> Signed-off-by: Rahul T R <r-ravikumar@ti.com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
> ---
>  .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> index c2b369456e4e..3a6c6d837593 100644
> --- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> @@ -57,6 +57,12 @@ properties:
>    interrupts:
>      maxItems: 1
>  
> +  cdns,no-hpd:
> +    type: boolean
> +    description:
> +      Set if the HPD line on the bridge isn't hooked up to anything or is
> +      otherwise unusable.

I'm fine with the non connected part, but concerned with "otherwise
unusable". It's very vague and could thus be abused. Do you have
particular use cases in mind for this ? If so, restricting this to those
use cases, or at least giving examples, would help.

> +
>    ports:
>      $ref: /schemas/graph.yaml#/properties/ports
>
  

On 05/04/2023 16:24, Jayesh Choudhary wrote:
> From: Rahul T R <r-ravikumar@ti.com>
> 
> The mhdp bridge can work without its HPD pin hooked up to the connector,
> but the current bridge driver throws an error when hpd line is not
> connected to the connector. For such cases, we need an indication for
> no-hpd, using which we can bypass the hpd detection and instead use the
> auxiliary channels connected to the DP connector to confirm the
> connection.
> So add no-hpd property to the bindings, to disable hpd when not
> connected or unusable.

Your subject prefixes miss device specific part. You do not add no-hpd
to all bridges.

It's also not drm. It is a display directory.

> 
> Signed-off-by: Rahul T R <r-ravikumar@ti.com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
> ---
>  .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> index c2b369456e4e..3a6c6d837593 100644
> --- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> @@ -57,6 +57,12 @@ properties:
>    interrupts:
>      maxItems: 1
>  
> +  cdns,no-hpd:

No improvements - use existing no-hpd name.



Best regards,
Krzysztof
  

On 06/04/23 07:10, Laurent Pinchart wrote:
> Hi Jayesh,
> 
> Thank you for the patch.
> 
> On Wed, Apr 05, 2023 at 07:54:39PM +0530, Jayesh Choudhary wrote:
>> From: Rahul T R <r-ravikumar@ti.com>
>>
>> The mhdp bridge can work without its HPD pin hooked up to the connector,
>> but the current bridge driver throws an error when hpd line is not
>> connected to the connector. For such cases, we need an indication for
>> no-hpd, using which we can bypass the hpd detection and instead use the
>> auxiliary channels connected to the DP connector to confirm the
>> connection.
>> So add no-hpd property to the bindings, to disable hpd when not
>> connected or unusable.
>>
>> Signed-off-by: Rahul T R <r-ravikumar@ti.com>
>> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
>> ---
>>   .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> index c2b369456e4e..3a6c6d837593 100644
>> --- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> @@ -57,6 +57,12 @@ properties:
>>     interrupts:
>>       maxItems: 1
>>   
>> +  cdns,no-hpd:
>> +    type: boolean
>> +    description:
>> +      Set if the HPD line on the bridge isn't hooked up to anything or is
>> +      otherwise unusable.
> 
> I'm fine with the non connected part, but concerned with "otherwise
> unusable". It's very vague and could thus be abused. Do you have
> particular use cases in mind for this ? If so, restricting this to those
> use cases, or at least giving examples, would help.

Okay. Will do that in next version.

Thanks.

> 
>> +
>>     ports:
>>       $ref: /schemas/graph.yaml#/properties/ports
>>   
>
  

On 11/04/23 11:36, Krzysztof Kozlowski wrote:
> On 05/04/2023 16:24, Jayesh Choudhary wrote:
>> From: Rahul T R <r-ravikumar@ti.com>
>>
>> The mhdp bridge can work without its HPD pin hooked up to the connector,
>> but the current bridge driver throws an error when hpd line is not
>> connected to the connector. For such cases, we need an indication for
>> no-hpd, using which we can bypass the hpd detection and instead use the
>> auxiliary channels connected to the DP connector to confirm the
>> connection.
>> So add no-hpd property to the bindings, to disable hpd when not
>> connected or unusable.
> 
> Your subject prefixes miss device specific part. You do not add no-hpd
> to all bridges.
> 
> It's also not drm. It is a display directory.

Sorry messed the commit heading. Will fix it.

> 
>>
>> Signed-off-by: Rahul T R <r-ravikumar@ti.com>
>> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
>> ---
>>   .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> index c2b369456e4e..3a6c6d837593 100644
>> --- a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> +++ b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
>> @@ -57,6 +57,12 @@ properties:
>>     interrupts:
>>       maxItems: 1
>>   
>> +  cdns,no-hpd:
> 
> No improvements - use existing no-hpd name.
> 
> 

Okay will change it to "no-hpd"

> 
> Best regards,
> Krzysztof
>