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Commit 6db90c59 authored by Douglas Anderson's avatar Douglas Anderson Committed by Ulf Hansson
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Documentation: mmc: sdhci-of-arasan: Add ability to export card clock 



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 frequency in order to
function properly.  Physically in a SoC this clock is exported from the
SDHCI IP block to the PHY IP block and the PHY needs to know the speed.
Let's export the SDHCI card clock using a standard device tree mechanism
so that the PHY can get access to it and query the card clock frequency.

Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Acked-by: default avatarRob Herring <robh@kernel.org>
Reviewed-by: default avatarHeiko Stuebner <heiko@sntech.de>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 3ea4666e

Documentation/devicetree/bindings/mmc/arasan,sdhci.txt

+8 −0
Original line number Diff line number Diff line
@@ -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@e0100000 {
@@ -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";

	};