[PATCH v5 2/3] mmc: sh_mobile_sdhi: explain clock bindings

[Chris Brandt <chris.brandt-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org>]

In the case of a single clock source, you don't need names. However,
if the controller has 2 clock sources, you need to name them correctly
so the driver can find the 2nd one. The 2nd clock is for the internal
card detect logic.

Signed-off-by: Chris Brandt <chris.brandt-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org>
---
v4:
* just explain there might be 2 clocks, don't explain how
  we will use them in the driver
v3:
* add more clarification about why there are sometimes 2 clocks
  and what you should do with them.
* remove 'status = "disabled"' from example
v2:
* fix spelling and change wording
* changed clock name from "carddetect" to "cd"
---
 Documentation/devicetree/bindings/mmc/tmio_mmc.txt | 24 ++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
index a1650ed..1464c16 100644
--- a/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/tmio_mmc.txt
@@ -25,8 +25,32 @@ Required properties:
 		"renesas,sdhi-r8a7795" - SDHI IP on R8A7795 SoC
 		"renesas,sdhi-r8a7796" - SDHI IP on R8A7796 SoC
 
+- clocks: Most controllers only have 1 clock source per channel. However, on
+	  some variations of this controller, the internal card detection
+	  logic that exists in this controller is sectioned off to be run by a
+	  separate second clock source to allow the main core clock to be turned
+	  off to save power.
+	  If 2 clocks are specified by the hardware, you must name them as
+	  "core" and "cd".
+	  If the controller only has 1 clock, naming is not required.
+
 Optional properties:
 - toshiba,mmc-wrprotect-disable: write-protect detection is unavailable
 - pinctrl-names: should be "default", "state_uhs"
 - pinctrl-0: should contain default/high speed pin ctrl
 - pinctrl-1: should contain uhs mode pin ctrl
+
+Example showing 2 clocks:
+	sdhi0: sd@e804e000 {
+		compatible = "renesas,sdhi-r7s72100";
+		reg = <0xe804e000 0x100>;
+		interrupts = <GIC_SPI 270 IRQ_TYPE_LEVEL_HIGH
+			      GIC_SPI 271 IRQ_TYPE_LEVEL_HIGH
+			      GIC_SPI 272 IRQ_TYPE_LEVEL_HIGH>;
+
+		clocks = <&mstp12_clks R7S72100_CLK_SDHI00>,
+			 <&mstp12_clks R7S72100_CLK_SDHI01>;
+		clock-names = "core", "cd";
+		cap-sd-highspeed;
+		cap-sdio-irq;
+	};
-- 
2.10.1


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