linux-kernel - Re: [PATCH v3 0/3] Convert Microchip's HLCDC Text based DT bindings to JSON schema

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Date: Thu, 18 Jan 2024 20:30:40 +0100
From: Sam Ravnborg <sam@...nborg.org>
To: Dharma Balasubiramani <dharma.b@...rochip.com>
Cc: conor.dooley@...rochip.com, bbrezillon@...nel.org,
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
	tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
	robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
	conor+dt@...nel.org, nicolas.ferre@...rochip.com,
	alexandre.belloni@...tlin.com, claudiu.beznea@...on.dev,
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	lee@...nel.org, thierry.reding@...il.com,
	u.kleine-koenig@...gutronix.de, linux-pwm@...r.kernel.org,
	linux4microchip@...rochip.com
Subject: Re: [PATCH v3 0/3] Convert Microchip's HLCDC Text based DT bindings
 to JSON schema

Hi Dharma et al.

On Thu, Jan 18, 2024 at 02:56:09PM +0530, Dharma Balasubiramani wrote:
> Converted the text bindings to YAML and validated them individually using following commands
> 
> $ make dt_binding_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/
> $ make dtbs_check DT_SCHEMA_FILES=Documentation/devicetree/bindings/
> 
> changelogs are available in respective patches.
> 
> Dharma Balasubiramani (3):
>   dt-bindings: display: convert Atmel's HLCDC to DT schema
>   dt-bindings: atmel,hlcdc: convert pwm bindings to json-schema
>   dt-bindings: mfd: atmel,hlcdc: Convert to DT schema format

I know this is a bit late to ask - sorry in advance.

The binding describes the single IP block as a multi functional device,
but it is a single IP block that includes the display controller and a
simple pwm that can be used for contrast or backlight.

If we ignore the fact that the current drivers for hlcdc uses an mfd
abstraction, is this then the optimal way to describe the HW?

In one of my stale git tree I converted atmel lcdc to DT, and here
I used:

+  "#pwm-cells":
+    description:
+      This PWM chip use the default 3 cells bindings
+      defined in ../../pwm/pwm.yaml.
+    const: 3
+
+  clocks:
+    maxItems: 2
+
+  clock-names:
+    maxItems: 2
+    items:
+      - const: lcdc_clk
+      - const: hclk

This proved to be a simple way to describe the HW.

To make the DT binding backward compatible you likely need to add a few
compatible that otherwise would have been left out - but that should do
the trick.

The current atmel hlcdc driver that is split in three is IMO an
over-engineering, and the driver could benefit merging it all in one.
And the binding should not prevent this.

	Sam