linux-kernel - Re: [PATCH 1/4] ARM: dts: exynos5250: Add #sound-dai-cells property to hdmi device node

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Message-id: <5AA5CE4F.6050807@samsung.com>
Date:   Mon, 12 Mar 2018 09:48:15 +0900
From:   Inki Dae <inki.dae@...sung.com>
To:     Sylwester Nawrocki <s.nawrocki@...sung.com>, krzk@...nel.org
Cc:     kgene@...nel.org, devicetree@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        b.zolnierkie@...sung.com, m.szyprowski@...sung.com
Subject: Re: [PATCH 1/4] ARM: dts: exynos5250: Add #sound-dai-cells property
 to hdmi device node

Hi Sylwester,

2018년 03월 09일 20:52에 Sylwester Nawrocki 이(가) 쓴 글:
> Hi Inki,
> 
> On 03/09/2018 03:40 AM, Inki Dae wrote:
>> 2018년 03월 08일 02:27에 Sylwester Nawrocki 이(가) 쓴 글:
>>> This property is required for specifying link between the HDMI IP block
>>> and the SoC's audio subsystem.
>>>
>>> Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
>>> ---
>>>  arch/arm/boot/dts/exynos5250.dtsi | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/arm/boot/dts/exynos5250.dtsi b/arch/arm/boot/dts/exynos5250.dtsi
>>> index 56626d1a4235..71d2ede118e3 100644
>>> --- a/arch/arm/boot/dts/exynos5250.dtsi
>>> +++ b/arch/arm/boot/dts/exynos5250.dtsi
>>> @@ -700,6 +700,7 @@
>>>  					"sclk_hdmiphy", "mout_hdmi";
>>>  			samsung,syscon-phandle = <&pmu_system_controller>;
>>>  			phy = <&hdmiphy>;
>>> +			#sound-dai-cells = <0>;
>>
>> This patch adds this property to hdmi device node which is bound by HDMI driver 
>> of Exynos DRM. As we talked about this at other email thread, seems this property 
>> is required mandatorily for Odroid XU3/4 board which uses Exynos5422.
>> There may be something I'm missing so could you let me know how this property 
>> is required?
> 
> It is required to properly interpret the list of DAI specified in the 'sound-dai'
> property. If a device supports only one DAI it will have #sound-dai-cells = <0>
> and the sound-dai property values in cpu<->codec link may look like this:
> 
>  cpu { ... }
>  codec {
> 	 sound-dai = <&max98090>, <&hdmi>;
>  };
> 
> When the CODEC support more DAIs it will have #sound-dai-cells = <1> and we can
> additionally specify which DAI we exactly refer to, in this case DAI 0:
> 
>  cpu { ... }
>  codec {
> 	sound-dai = <&max98095 0>, <&hdmi>;
>  };
> 
> More details can be found in documentation of of_parse_phandle_with_args()
> function.
> 
> The above refers to cpu/codec mapping like I2S0 -> [max9809x, hdmi], on Exynos5433
> we have I2S0 -> wm5110 and I2S1 -> hdmi.

Thanks for explanation. By the way, who binds '#sound-dai-cells' property?.
This patch adds this property to hdmi device node which will be bound by HDMI driver fo Exynos DRM but I don't see any place to bind '#sound-dai-cells' property in this driver.
So I think some driver like Odroid XU3/4 audio driver(sound/soc/samsung/odroid.c) or ASoC simple audio card driver(sound/soc/generic/simple-card.c) should exist and this property should be placed to such device node.

Thanks,
Inki Dae

> 
>