linux-kernel - Re: [PATCH v2 1/2] dt-bindings: display: rockchip: Add compatible for rk3568 HDMI

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Message-ID: <3865833.Ac65pObt5d@diego>
Date:   Tue, 13 Jul 2021 10:49:37 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        hjc@...k-chips.com, airlied@...ux.ie, daniel@...ll.ch,
        robh+dt@...nel.org, algea.cao@...k-chips.com,
        andy.yan@...k-chips.com,
        Michael Riesch <michael.riesch@...fvision.net>
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v2 1/2] dt-bindings: display: rockchip: Add compatible for rk3568 HDMI

Hi Michael,

Am Dienstag, 13. Juli 2021, 10:44:00 CEST schrieb Michael Riesch:
> The HDMI TX block in the RK3568 requires two power supplies, which have
> to be enabled in some cases (at least on the RK3568 EVB1 the voltages
> VDDA0V9_IMAGE and VCCA1V8_IMAGE are disabled by default). It would be
> great if this was considered by the driver and the device tree binding.
> I am not sure, though, whether this is a RK3568 specific or
> rockchip_dw_hdmi specific thing. Maybe it can even enter the Synopsis DW
> HDMI driver.

I do remember that this discussion happened many years back already.
And yes the supplies are needed for all but back then there was opposition
as these are supposedly phy-related supplies, not for the dw-hdmi itself.
[There are variants with an external phy, like on the rk3328]

See discussion on [0]

[0] https://dri-devel.freedesktop.narkive.com/pen2zWo1/patch-v3-1-2-drm-bridge-dw-hdmi-support-optional-supply-regulators



> On 7/7/21 2:03 PM, Benjamin Gaignard wrote:
> > Define a new compatible for rk3568 HDMI.
> > This version of HDMI hardware block needs two new clocks hclk_vio and hclk
> > to provide phy reference clocks.
> > 
> > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> > ---
> > version 2:
> > - Add the clocks needed for the phy.
> > 
> >  .../bindings/display/rockchip/rockchip,dw-hdmi.yaml         | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-hdmi.yaml b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-hdmi.yaml
> > index 75cd9c686e985..cb8643b3a8b84 100644
> > --- a/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-hdmi.yaml
> > +++ b/Documentation/devicetree/bindings/display/rockchip/rockchip,dw-hdmi.yaml
> > @@ -23,6 +23,7 @@ properties:
> >        - rockchip,rk3288-dw-hdmi
> >        - rockchip,rk3328-dw-hdmi
> >        - rockchip,rk3399-dw-hdmi
> > +      - rockchip,rk3568-dw-hdmi
> >  
> >    reg-io-width:
> >      const: 4
> > @@ -51,8 +52,11 @@ properties:
> >            - vpll
> >        - enum:
> >            - grf
> > +          - hclk_vio
> > +          - vpll
> > +      - enum:
> > +          - hclk
> >            - vpll
> > -      - const: vpll
> 
> The description and documentation of the clocks are somewhat misleading
> IMHO. This is not caused by your patches, of course. But maybe this is a
> chance to clean them up a bit.
> 
> It seems that the CEC clock is an optional clock of the dw-hdmi driver.
> Shouldn't it be documented in the synopsys,dw-hdmi.yaml?
> 
> Also, it would be nice if the clocks hclk_vio and hclk featured a
> description in the binding.
> 
> BTW, I am not too familiar with the syntax here, but shouldn't items in
> clocks and items in clock-names be aligned (currently, there is a plain
> list vs. an enum structure)?
> 
> Best regards,
> Michael
> 
> >  
> >    ddc-i2c-bus:
> >      $ref: /schemas/types.yaml#/definitions/phandle
> > 
>