Message-ID: <b8e3d087-271a-476d-986f-ad3f08231136@ti.com>
Date: Thu, 15 Jan 2026 22:24:41 +0530
From: Swamil Jain <s-jain1@...com>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: <jyri.sarha@....fi>, <tomi.valkeinen@...asonboard.com>,
	<airlied@...il.com>, <simona@...ll.ch>, <maarten.lankhorst@...ux.intel.com>,
	<mripard@...nel.org>, <tzimmermann@...e.de>, <robh@...nel.org>,
	<krzk+dt@...nel.org>, <conor+dt@...nel.org>, <aradhya.bhatia@...ux.dev>,
	<dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devarsht@...com>, <praneeth@...com>,
	<h-shenoy@...com>, <u-kumar1@...com>
Subject: Re: [PATCH v3 1/3] dt-bindings: display: ti,am65x-dss: Add am62p dss
 compatible

Hi Krzysztof,

On 1/8/26 14:21, Krzysztof Kozlowski wrote:
> On Wed, Jan 07, 2026 at 11:15:23PM +0530, Swamil Jain wrote:
>> TI's AM62P SoC contains two instances of the TI Keystone Display
>> SubSystem (DSS), each with two video ports and two video planes. These
>> instances support up to three independent video streams through OLDI,
>> DPI, and DSI interfaces.
>>
>> DSS0 (first instance) supports:
>>   - Two OLDI transmitters on video port 1, configurable in dual-link or
>>     single-link mode.
>>   - DPI output on video port 2.
>>
>> DSS1 (second instance) supports:
>>   - One OLDI transmitter on video port 1 (single-link mode only).
>>   - DSI controller output on video port 2.
>>
>> The two OLDI transmitters can be configured in clone mode to drive a
>> pair of identical OLDI single-link displays. DPI outputs from
>> DSS0 VP2, DSS1 VP1, and DSS1 VP2 are multiplexed, allowing only one
>> DPI output at a time.
>>
>> Add the compatible string "ti,am62p-dss" and update related
>> description accordingly.
>>
>> AM62P has different power domains for DSS and OLDI compared to other
>> Keystone SoCs. Therefore, add 'minItems' and set to 1 and 'maxItems'
>> field in the power-domains property to 3 for the "ti,am62p-dss"
>> compatible entry to reflect this hardware difference.
> 
> Last sentence is redundant. You are again explain repeating the diff
> which is pointless, but did not explain WHY you think 2 power domains is
> correct.
> 

Will explain properly in the commit message why 2 power domains are 
correct in v4.

>>
>> Signed-off-by: Swamil Jain <s-jain1@...com>
>> ---
>>   .../bindings/display/ti/ti,am65x-dss.yaml     | 33 ++++++++++++++++++-
>>   1 file changed, 32 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> index 38fcee91211e..e74e710934fc 100644
>> --- a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> +++ b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> @@ -24,6 +24,19 @@ description: |
>>     DPI signals are also routed internally to DSI Tx controller present within the
>>     SoC. Due to clocking limitations only one of the interface i.e. either DSI or
>>     DPI can be used at once.
>> +  The AM62P has two instances of TI Keystone Display SubSystem, each with two
>> +  video ports and two video planes. These instances can support up to 3
>> +  independent video streams through OLDI, DPI, and DSI interfaces.
>> +  DSS0 (first instance) supports:
>> +    - Two OLDI TXes on video port 1, configurable in dual-link or
>> +      single link clone mode
>> +    - DPI output on video port 2
>> +  DSS1 (second instance) supports:
>> +    - One OLDI TX on video port 1 (single-link mode only)
>> +    - DSI controller output on video port 2
>> +  The two OLDI TXes can be configured in clone mode to drive a pair of
>> +  identical OLDI single-link displays. DPI outputs from DSS0 VP2, DSS1 VP1,
>> +  and DSS1 VP2 are muxed, allowing only one DPI output at a time.
>>   
>>   properties:
>>     compatible:
>> @@ -31,6 +44,7 @@ properties:
>>         - ti,am625-dss
>>         - ti,am62a7-dss
>>         - ti,am62l-dss
>> +      - ti,am62p-dss
>>         - ti,am65x-dss
>>   
>>     reg:
>> @@ -81,7 +95,8 @@ properties:
>>       maxItems: 1
>>   
>>     power-domains:
>> -    maxItems: 1
>> +    minItems: 1
>> +    maxItems: 3
>>       description: phandle to the associated power domain
>>   
>>     dma-coherent: true
>> @@ -196,6 +211,22 @@ allOf:
>>                 properties:
>>                   endpoint@1: false
>>   
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            const: ti,am62p-dss
>> +    then:
>> +      properties:
>> +        power-domains:
>> +          minItems: 1
>> +          maxItems: 3
> 
> This is still not constrained enough. You need to define the items
> instead. I still do not understand why number of power domains is
> flexible.

Planning to add:
```
power-domains:
   minItems: 1
   description:
     phandle to the associated power domain(s).
   items:
     - description: DSS controller power domain
     - description: OLDI0 power domain
     - description: OLDI1 power domain
```

There can be up to 3 power-domains in a DSS instance on AM62P SoC.
Please check the Technical Reference Manual for AM62P SoC[0].
On page 542 it is mentioned LPSC_main_dss0 has a partial dependence
on LPSC_main_oldi0 and LPSC_main_oldi1, and, similarly for
LPSC_main_dss1 there is a partial dependence on LPSC_main_oldi1.
This mean if you are only enabling DSS0 Video port 1 for HDMI output
only you need not mention other power-domains and similarly for DSS1
if you need OLDI1 output you need to use DSS1 and OLDI1 power-domains.
So, we can use up to 3 power-domains depending on the use-case.

[0]: https://www.ti.com/lit/ug/spruj83c/spruj83c.pdf
> 
>> +    else:
>> +      properties:
>> +        power-domains:
>> +          minItems: 1
> 
> You can drop this one.
> 

Yeah, sure will drop this in v4.

>> +          maxItems: 1
>> +
>>   required:
>>     - compatible
>>     - reg

Regards,
Swamil.

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