linux-kernel - Re: [PATCH 06/11] Documentation: mmc: sdhci-of-arasan: Add ability to export card clock

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Message-ID: <20160608201923.GA20683@rob-hp-laptop>
Date:	Wed, 8 Jun 2016 15:19:23 -0500
From:	Rob Herring <robh@...nel.org>
To:	Douglas Anderson <dianders@...omium.org>
Cc:	ulf.hansson@...aro.org, kishon@...com,
	Heiko Stuebner <heiko@...ech.de>, shawn.lin@...k-chips.com,
	xzy.xu@...k-chips.com, briannorris@...omium.org,
	adrian.hunter@...el.com, linux-rockchip@...ts.infradead.org,
	linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/11] Documentation: mmc: sdhci-of-arasan: Add ability
 to export card clock

On Tue, Jun 07, 2016 at 03:44:39PM -0700, Douglas Anderson wrote:
> Some SD/eMMC PHYs (like the PHY from Arasan that is designed to work
> with arasan,sdhci-5.1) need to know the card clock in order to function
> properly.  Let's expose this clock using a standard device tree
> mechanism so that the PHY can get access to and query the card clock.

Need to know the clock freq or need the clock? The former doesn't need 
to be in DT.

> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>  Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> index b67e623ca1ff..074d03e630ec 100644
> --- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> +++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
> @@ -30,6 +30,12 @@ Optional Properties:
>    - arasan,soc-ctl-syscon: A phandle to a syscon device (see ../mfd/syscon.txt)
>      used to access core corecfg registers.  Offsets of registers in this
>      syscon are determined based on the main compatible string for the device.
> +  - clock-output-names: If specified, this will be the name of the card clock
> +    which will be exposed by this device.  Required if #clock-cells is
> +    specified.
> +  - #clock-cells: If specified this should be the value <0>.  With this property
> +    in place we will export a clock representing the Card Clock.  This clock
> +    is expected to be consumed by our PHY.  You must also specify
>  
>  Example:
>  	sdhci@...00000 {
> @@ -61,7 +67,9 @@ Example:
>  		arasan,soc-ctl-syscon = <&grf>;
>  		assigned-clocks = <&cru SCLK_EMMC>;
>  		assigned-clock-rates = <200000000>;
> +		clock-output-names = "emmc_cardclock";
>  		phys = <&emmc_phy>;
>  		phy-names = "phy_arasan";
> +		#clock-cells = <0>;
>  		status = "disabled";
>  	};
> -- 
> 2.8.0.rc3.226.g39d4020
>