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

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Date:   Tue, 13 Jul 2021 10:44:00 +0200
From:   Michael Riesch <michael.riesch@...fvision.net>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        hjc@...k-chips.com, heiko@...ech.de, airlied@...ux.ie,
        daniel@...ll.ch, robh+dt@...nel.org, algea.cao@...k-chips.com,
        andy.yan@...k-chips.com
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

Hello Benjamin,

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.

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
>