linux-kernel - Re: [PATCH v7 1/3] dt-bindings: soc: imx93-media-blk-ctrl: Add PDFC subnode to schema and example

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Message-ID: <20251219153537.zgxcokyhcqerw4jp@pengutronix.de>
Date: Fri, 19 Dec 2025 16:35:37 +0100
From: Marco Felsch <m.felsch@...gutronix.de>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Liu Ying <victor.liu@....com>, krzk+dt@...nel.org,
	Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, Peng Fan <peng.fan@....com>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.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>,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v7 1/3] dt-bindings: soc: imx93-media-blk-ctrl: Add PDFC
 subnode to schema and example

Hi Krzysztof, Rob,

On 25-12-18, Krzysztof Kozlowski wrote:
> On 15/12/2025 17:17, Marco Felsch wrote:
> > Hi Liu,
> > 
> > On 25-12-08, Liu Ying wrote:
> >> Hi Marco,
> >>
> >> On 12/02/2025, Marco Felsch wrote:
> >>> From: Liu Ying <victor.liu@....com>
> >>>
> >>> i.MX93 SoC mediamix blk-ctrl contains one DISPLAY_MUX register which
> >>> configures parallel display format by using the "PARALLEL_DISP_FORMAT"
> >>> field. Document the Parallel Display Format Configuration(PDFC) subnode
> >>> and add the subnode to example.
> >>>
> >>> Signed-off-by: Liu Ying <victor.liu@....com>
> >>> [m.felsch@...gutronix.de: port to v6.18-rc1]
> >>> [m.felsch@...gutronix.de: add bus-width]
> >>> Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> >>> ---
> >>>  .../bindings/soc/imx/fsl,imx93-media-blk-ctrl.yaml | 92 ++++++++++++++++++++++
> >>>  1 file changed, 92 insertions(+)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/soc/imx/fsl,imx93-media-blk-ctrl.yaml b/Documentation/devicetree/bindings/soc/imx/fsl,imx93-media-blk-ctrl.yaml
> >>> index 34aea58094e55365a2f9c86092f637e533f954ff..6e2d86d9341c75108b492bcbabc8a560d8e707cd 100644
> >>> --- a/Documentation/devicetree/bindings/soc/imx/fsl,imx93-media-blk-ctrl.yaml
> >>> +++ b/Documentation/devicetree/bindings/soc/imx/fsl,imx93-media-blk-ctrl.yaml
> >>> @@ -26,6 +26,12 @@ properties:
> >>>    reg:
> >>>      maxItems: 1
> >>>  
> >>> +  '#address-cells':
> >>> +    const: 1
> >>> +
> >>> +  '#size-cells':
> >>> +    const: 1
> >>> +
> >>>    '#power-domain-cells':
> >>>      const: 1
> >>>  
> >>> @@ -40,6 +46,60 @@ properties:
> >>>      minItems: 8
> >>>      maxItems: 10
> >>>  
> >>> +  bridge@60:
> >>
> >> The dependency patch series mentioned in cover letter has two links in it's
> >> cover letter.  Reading the patch sets pointed by the two links, we may find
> >> Krzysztof's comments - the child nodes of the blk-ctrl should be completely
> >> documented.
> > 
> > Thanks for pointing this out.
> > 
> > @Krzysztof
> > Requesting to add everything seems not feasible if everything added
> > should be tested too.
> > I don't see why everything should be added in one step, since the base
> > .dtsi isn't added in one step too.
> 
> Because otherwise we do not see entire picture and people post incorrect
> bindings, claiming they are complete picture, like messing nodes with
> addressing and nodes without. So sure, if you do not want to post
> complete picture, we cannot review that complete picture, therefore YOU
> MUST POST CORRECT CODE.
> 
> I will not be taking excuses later "we did not know that such code is
> not allowed". You must know all rules.

We discussed the ranges/reg usage internally as well with the following
outcome:

- Situation

  With i.MX8M SoCs NXP introduced MIX domains. Each domain has a so
  called BLK-CTRL IP. There is no common register layout for the
  BLK-CTRL IPs. In addition to this, the register fields within one
  register may not related to the same IP. Please see my below example:
  
  The DISP_MUX register configures the DPI output routed to physical
  SoC pads as well as the internal MIPI-DSI DPI behavior. This PDFC
  bridge binding is only interested in the first part, not the 2nd.

  In other words, the BLK-CTRL IP can be seen as a bunch of loose
  register fields.

- Our outcome

  To be future compatible and extentible, we believe that the best
  abstraction is the syscon, no mappings (no ranges/regs). A BLK-CTRL
  sub-device has no address, just the node name. The driver needs to rely
  on the syscon parent device. All register(-field) handling is done
  within the sub-device driver.

  This way new functionallity like MIPI-DSI PLL clock provider driver
  can be added easily.

I will adapt this patchset accordingly, if you agree to rely on the
syscon (no regs/ranges).

Regards,
  Marco


> 
> 
> Best regards,
> Krzysztof
> 

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