linux-kernel - Re: [PATCH v4 2/4] dt-bindings: media: Document bindings for HDMI RX Controller

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Message-ID: <cf8c1764-7721-4a5a-8012-b62ead4e2e57@wolfvision.net>
Date: Mon, 26 Aug 2024 10:19:06 +0200
From: Michael Riesch <michael.riesch@...fvision.net>
To: Shreeya Patel <shreeya.patel@...labora.com>, heiko@...ech.de,
 mchehab@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, mturquette@...libre.com, sboyd@...nel.org,
 p.zabel@...gutronix.de, jose.abreu@...opsys.com, nelson.costa@...opsys.com,
 shawn.wen@...k-chips.com, nicolas.dufresne@...labora.com,
 hverkuil@...all.nl, hverkuil-cisco@...all.nl
Cc: kernel@...labora.com, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 Dmitry Osipenko <dmitry.osipenko@...labora.com>
Subject: Re: [PATCH v4 2/4] dt-bindings: media: Document bindings for HDMI RX
 Controller

Hi Shreeya, hi all,

First of all thank you very much for your efforts and patches!

I have got more of a general question that came up during my recent work
on a HDMI RX companion chip driver. It may or may not be out of scope of
this initial submission for the Synopsys HDMI RX IP core, but anyway I
feel like I should ask it now:

On 7/19/24 14:40, Shreeya Patel wrote:
> [...]
> +examples:
> +  - |
> +    #include <dt-bindings/clock/rockchip,rk3588-cru.h>
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +    #include <dt-bindings/power/rk3588-power.h>
> +    #include <dt-bindings/reset/rockchip,rk3588-cru.h>
> +    hdmi_receiver: hdmi-receiver@...e0000 {
> +      compatible = "rockchip,rk3588-hdmirx-ctrler", "snps,dw-hdmi-rx";
> +      reg = <0xfdee0000 0x6000>;
> +      interrupts = <GIC_SPI 177 IRQ_TYPE_LEVEL_HIGH 0>,
> +                   <GIC_SPI 436 IRQ_TYPE_LEVEL_HIGH 0>,
> +                   <GIC_SPI 179 IRQ_TYPE_LEVEL_HIGH 0>;
> +      interrupt-names = "cec", "hdmi", "dma";
> +      clocks = <&cru ACLK_HDMIRX>,
> +               <&cru CLK_HDMIRX_AUD>,
> +               <&cru CLK_CR_PARA>,
> +               <&cru PCLK_HDMIRX>,
> +               <&cru CLK_HDMIRX_REF>,
> +               <&cru PCLK_S_HDMIRX>,
> +               <&cru HCLK_VO1>;
> +      clock-names = "aclk",
> +                    "audio",
> +                    "cr_para",
> +                    "pclk",
> +                    "ref",
> +                    "hclk_s_hdmirx",
> +                    "hclk_vo1";
> +      power-domains = <&power RK3588_PD_VO1>;
> +      resets = <&cru SRST_A_HDMIRX>, <&cru SRST_P_HDMIRX>,
> +               <&cru SRST_HDMIRX_REF>, <&cru SRST_A_HDMIRX_BIU>;
> +      reset-names = "axi", "apb", "ref", "biu";
> +      memory-region = <&hdmi_receiver_cma>;
> +      pinctrl-0 = <&hdmim1_rx_cec &hdmim1_rx_hpdin &hdmim1_rx_scl &hdmim1_rx_sda &hdmirx_5v_detection>;
> +      pinctrl-names = "default";
> +      hpd-gpios = <&gpio1 22 GPIO_ACTIVE_LOW>;
> +    };

Should HDMI RX connectors be described in the device tree?

It seems that V4L2 features support for svidio and composite connectors,
but newer standards such as HDMI never made it to e.g,
drivers/media/v4l2-core/v4l2-fwnode.c. The name of the corresponding DT
binding
Documentation/devicetree/bindings/display/connector/analog-tv-connector.yaml
somewhat confirms that only analog connectors are in the scope there.
This means that some initial discussion and effort on the framework
would be required.

However, this would enable some nice (although not exactly killer)
features: describing label, orientation, and connector (sub)type on DT
level, thus eliminating the need to know the HW description in the
higher SW layers.

If the notion of HDMI RX (or, in general, digital video input)
connectors in DT sounds reasonable to you all, there may be the chance
to rework the submission at hand accordingly to avoid any compatibility
issues with older/newer device trees. This is why I am bringing this up
right now.

What do you all think?

Best regards,
Michael