linux-kernel - Re: [PATCH 1/4] dt-bindings: display: ti,am65x-dss: Add clk property for data edge synchronization

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Message-ID: <28715810-1279-45ad-b978-f991ecf49c70@bootlin.com>
Date: Thu, 31 Jul 2025 11:50:11 +0200
From: Louis Chauvet <louis.chauvet@...tlin.com>
To: Rob Herring <robh@...nel.org>
Cc: Jyri Sarha <jyri.sarha@....fi>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Sam Ravnborg <sam@...nborg.org>,
 Benoit Parrot <bparrot@...com>, Lee Jones <lee@...nel.org>,
 Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Tero Kristo <kristo@...nel.org>, thomas.petazzoni@...tlin.com,
 Jyri Sarha <jsarha@...com>, Tomi Valkeinen <tomi.valkeinen@...com>,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 stable@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: display: ti,am65x-dss: Add clk property
 for data edge synchronization



Le 31/07/2025 à 01:56, Rob Herring a écrit :
> On Wed, Jul 30, 2025 at 07:02:44PM +0200, Louis Chauvet wrote:
>> The dt-bindings for the display, specifically ti,am65x-dss, need to
>> include a clock property for data edge synchronization. The current
>> implementation does not correctly apply the data edge sampling property.
>>
>> To address this, synchronization of writes to two different registers is
>> required: one in the TIDSS IP (which is already described in the tidss
>> node) and one is in the Memory Mapped Control Register Modules (added by
>> the previous commit).
>>
>> As the Memory Mapped Control Register Modules is located in a different
>> IP, we need to use a phandle to write values in its registers.
> 
> You can always just lookup the target node by compatible. Then you don't
> need a DT update to solve your problem.

I just followed what was already done for dss_oldi_io_ctrl/ti,oldi-io-ctrl.

I will use syscon_regmap_lookup_by_compatible for the v2.

>>
>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
>> Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>
>>
>> ---
>>
>> Cc: stable@...r.kernel.org
>> ---
>>   Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> index 361e9cae6896c1f4d7fa1ec47a6e3a73bca2b102..b9a373b569170332f671416eb7bbc0c83f7b5ea6 100644
>> --- a/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> +++ b/Documentation/devicetree/bindings/display/ti/ti,am65x-dss.yaml
>> @@ -133,6 +133,12 @@ properties:
>>         and OLDI_CLK_IO_CTRL registers. This property is needed for OLDI
>>         interface to work.
>>   
>> +  ti,clk-ctrl:
>> +    $ref: /schemas/types.yaml#/definitions/phandle
>> +    description:
>> +      phandle to syscon device node mapping CFG0_CLK_CTRL registers.
>> +      This property is needed for proper data sampling edge.
>> +
>>     max-memory-bandwidth:
>>       $ref: /schemas/types.yaml#/definitions/uint32
>>       description:
>>
>> -- 
>> 2.50.1
>>

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com