linux-kernel - Re: [PATCH] arm64: dts: rockchip: Add avdd supplies to hdmi on rock64

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Message-ID: <6192146.IJkX0fH94T@bagend>
Date: Mon, 08 Jul 2024 11:55:07 +0200
From: Diederik de Haas <didi.debian@...ow.org>
To: Dragan Simic <dsimic@...jaro.org>
Cc: Heiko Stuebner <heiko@...ech.de>, Alex Bee <knaerzche@...il.com>,
 linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: rockchip: Add avdd supplies to hdmi on rock64

Hi Dragan,

On Sunday, 7 July 2024 23:23:30 CEST Dragan Simic wrote:
> On 2024-07-04 21:18, Diederik de Haas wrote:
> > Pine64's Rock64 was missing the avdd supply properties on the hdmi
> > node,
> > 
> > causing the following warnings:
> >   dwhdmi-rockchip ff3c0000.hdmi: supply avdd-0v9 not found, using
> > dummy regulator
> > 
> >   dwhdmi-rockchip ff3c0000.hdmi: supply avdd-1v8 not found, using
> > dummy regulator
> > 
> > In the Rock64 Schematic document version 2.0 those supplies are marked
> > as DVIDEO_AVDD_1V0 and DVIDEO_AVDD_1V8 respectively, but in version 3.0
> > those are named HDMI_AVDD_1V0 and HDMI_AVDD_1V8, which is a bit
> > clearer.
> > In both versions those are connected to LDO3 and LDO1 respectively.
> > 
> > While the DeviceTree property is named 'avdd-0v9-supply' the
> > 
> > 'rockchip,dw-hdmi.yaml' binding document notes the following:
> >   A 0.9V supply that powers up the SoC internal circuitry. The actual
> >   pin name varies between the different SoCs and is usually
> >   HDMI_TX_AVDD_0V9 or sometimes HDMI_AVDD_1V0.
> > 
> > So the 'vdd_10' reference is not an error.
> > 
> > Signed-off-by: Diederik de Haas <didi.debian@...ow.org>
> 
> Already verified the above-quoted statement from the .yaml binding
> in the RK3328 and RK3399 datasheets.  Thus, hoping that you agree
> with the first line:
> 
> Helped-by: Dragan Simic <dsimic@...jaro.org>

While you helped me in several areas (understanding 'things') and I think 
proper attribution is very important, in this case it would be incorrect IMO.
I was helped by Heiko's (big) hint in their counter-proposal (which does 
deserve a Helped-by tag), from that point on, it was all my own work.

After Heiko's counter-proposal I had found the regulator I needed to 
reference. I then resolved the DVIDEO vs HDMI remark by looking at v2 and v3 
of the Schematic document. Which left 1 thing to resolve ...

On Thursday, 4 July 2024 12:34:18 CEST Diederik de Haas wrote:
> I do wonder about 0.9V vs 1.0V, but I'll bug someone else about that ;-)

I did mean you with that, but in the end I did resolve it myself.
I found the 'note' in the binding document and when I then found "min: 0.9; 
typical: 1.0; max: 1.1" in para 3.2 (page 36) of the RK3328 Datasheet, I felt 
I had resolved that issue sufficiently as well and was confident enough to sent 
the patch out (without sending you a RFC patch first).

> Reviewed-by: Dragan Simic <dsimic@...jaro.org>

Thanks :-)

> I'd also suggest that a brief comment is added to rk3328-rock64.dts,
> right above the "avdd-0v9-supply = <&vdd_10>;" line.  Perhaps something
> 
> like this:
> > +	/*
> > +	 * RK3328 requires 1.0 V on HDMI_AVDD_1V0, which is HDMI_AVDD_0V9
> > +	 * and requires 0.9 V on other Rockchip SoCs
> > +	 */

The binding doc mention this: "The actual pin name varies between the different 
SoCs and is *usually* HDMI_TX_AVDD_0V9" (emphasis mine)

So that comment would make stronger claims then is present in the binding 
document and also uses a different pin name. I also don't think it's useful to 
mention what other SoCs (or boards) use in the rk3328-rock64.dts.

While I fully agree that the apparent discrepancy should be documented, I 
choose to do that in the commit message and I don't see a value to repeat that 
in the dts file itself.
When I see something which looks 'odd', I'd then use `git blame` to find the 
commit which set that and then I'd see the commit message which explains it.

Cheers,
  Diederik

> > ---
> > 
> >  arch/arm64/boot/dts/rockchip/rk3328-rock64.dts | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3328-rock64.dts
> > b/arch/arm64/boot/dts/rockchip/rk3328-rock64.dts
> > index 229fe9da9c2d..90fef766f3ae 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3328-rock64.dts
> > +++ b/arch/arm64/boot/dts/rockchip/rk3328-rock64.dts
> > @@ -154,6 +154,8 @@ &gmac2io {
> > 
> >  };
> >  
> >  &hdmi {
> > 
> > +	avdd-0v9-supply = <&vdd_10>;
> > +	avdd-1v8-supply = <&vcc_18>;
> > 
> >  	status = "okay";
> >  
> >  };

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