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: Douglas Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Rob Herring <robh@xxxxxxxxxx>
Reviewed-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
Changes in v3:
- Add collected tags
Changes in v2:
- Adjust commit message wording (Rob)
- Add Rob Herring's Ack.
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 476604e6ce2a..3404afa9b938 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@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";
};
--
2.8.0.rc3.226.g39d4020
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