linux-kernel - Re: [PATCH 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl property

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Message-ID: <20250805-imperial-bobcat-of-improvement-5cf705@kuoka>
Date: Tue, 5 Aug 2025 08:44:20 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Louis Chauvet <louis.chauvet@...tlin.com>
Cc: Rob Herring <robh@...nel.org>, 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 3/4] arm64: dts: ti: k3-am62-main: Add tidss clk-ctrl
 property

On Thu, Jul 31, 2025 at 11:50:16AM +0200, Louis Chauvet wrote:
> 
> 
> Le 31/07/2025 à 02:17, Rob Herring a écrit :
> > On Wed, Jul 30, 2025 at 07:02:46PM +0200, Louis Chauvet wrote:
> > > For am62 processors, we need to use the newly created clk-ctrl property to
> > > properly handle data edge sampling configuration. Add them in the main
> > > device tree.
> > > 
> > > 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
> > > ---
> > >   arch/arm64/boot/dts/ti/k3-am62-main.dtsi | 6 ++++++
> > >   1 file changed, 6 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > index 9e0b6eee9ac77d66869915b2d7bec3e2275c03ea..d3131e6da8e70fde035d3c44716f939e8167795a 100644
> > > --- a/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > +++ b/arch/arm64/boot/dts/ti/k3-am62-main.dtsi
> > > @@ -76,6 +76,11 @@ audio_refclk1: clock-controller@...4 {
> > >   			assigned-clock-parents = <&k3_clks 157 18>;
> > >   			#clock-cells = <0>;
> > >   		};
> > > +
> > > +		dss_clk_ctrl: dss_clk_ctrl@...0 {
> > > +			compatible = "ti,am625-dss-clk-ctrl", "syscon";
> > > +			reg = <0x8300 0x4>;
> > 
> > H/w blocks are rarely only 4 bytes of registers... Does this belong to
> > some larger block. The problem with bindings defining single registers
> > like this is they don't get defined until needed and you have a constant
> > stream of DT updates.
> 
> In this case, I don't think there is a "larger block". This register exists
> only because TI had issues in the display controller [1].
> 
> Here is the extract of MMR registers ([2], page 4311):
> 
> [...]
> A2E4h AUDIO_REFCLK1_CTRL_PROXY <unrelated>

Here is clk ctrl proxy...

> A300h DPI0_CLK_CTRL_PROXY <this register, 32 bits>

and here as well, so pretty related. This looks also close to regular
syscon and we do not define individual syscon registers as device nodes.

Best regards,
Krzysztof