On 03/28/2013 06:43 AM, Kishon Vijay Abraham I wrote:
diff --git a/Documentation/devicetree/bindings/phy/phy-bindings.txt
b/Documentation/devicetree/bindings/phy/phy-bindings.txt
new file mode 100644
index 0000000..35696b2
--- /dev/null
+++ b/Documentation/devicetree/bindings/phy/phy-bindings.txt
@@ -0,0 +1,76 @@
+This document explains only the dt data binding. For general information about
+PHY subsystem refer Documentation/phy.txt
+
+PHY device node
+===============
+
+Optional Properties:
+#phy-cells: Number of cells in a PHY specifier; The meaning of all those
+ cells is defined by the binding for the phy node. However
+ in-order to return the correct PHY, the PHY susbsystem
+ requires the first cell always refers to the port.
+
+This property is optional because it is needed only for the case where a
+single IP implements multiple PHYs.
+
+For example:
+
+phys: phy {
+ compatible = "xxx";
+ reg1 =<...>;
+ reg2 =<...>;
+ reg3 =<...>;
+ .
+ .
+ #phy-cells =<1>;
+ .
+ .
+};
+
+That node describes an IP block that implements 3 different PHYs. In order to
+differentiate between these 3 PHYs, an additonal specifier should be given
+while trying to get a reference to it. (The PHY subsystem assumes the
+specifier is port id).
+
+PHY user node
+=============
+
+Required Properties:
+phys : the phandle for the PHY device (used by the PHY subsystem)
+
+Optional properties:
+phy-names : the names of the PHY corresponding to the PHYs present in the
+ *phys* phandle
+
+example1:
+phys: phy {
+ compatible = "xxx";
+ reg =<...>;
+ .
+ .
+ phys =<&usb2_phy>,<&usb3_phy>;
+ phy-names = "usb2phy", "usb3phy";
+ .
+ .
+};
+This node represents a controller that uses two PHYs one for usb2 and one for
+usb3. The controller driver can get the appropriate PHY either by using
+devm_of_phy_get/of_phy_get by passing the correct index or by using
+of_phy_get_byname/devm_of_phy_get_byname by passing the names given in
+*phy-names*.
+
+example2:
+phys: phy {
+ compatible = "xxx";
+ reg =<...>;
+ .
+ .
+ phys =<&phys 1>;
+ .
+ .
+};
+
+This node represents a controller that uses one of the PHYs which is defined
+previously. Note that the phy handle has an additional specifier "1" to
+differentiate between the three PHYs. For this case, the controller driver
+should use of_phy_get_with_args/devm_of_phy_get_with_args.
This means a PHY user needs to know indexes at the PHY driver ?
I have been thinking of using this for an IP which has 4 video PHYs: 2 MIPI
CSI-2 and 2 MIPI DSI. The IP has just 2 registers, each of which is shared
between one MIPI CSI-2 DPHY and one MIPI DSI DPHY. So I thought about
creating
a single device node for this IP and using 4 indexes for the PHYs, e.g.
0...3.
Then users of each PHY type would use only indexes 0..1 (to select their
corresponding port).
However I fail to see how this could now be represented in the bindings.
I assume struct phy::type could be used to differentiate between CSI-2
and DSI.
And struct phy::port could be used to select specific CSI-2 or DSI channel
(0, 1). Ideally the phy users should not care about index of a PHY at
the PHY
device tree node. E.g. there are 2 MIPI CSI-2 receivers and each has only
one PHY assigned to it. I'm just wondering how the binding should look like,
so a PHY could be associated with a receiver automatically by the phy-core,
e.g.
/* DPHY IP node */
video-phy {
reg = <0x10000000 8>;
};
/* MIPI DSI nodes */
dsi_0 {
phys = <&video-phy 0>;
};
dsi_1 {
phys = <&video-phy 1>;
};
/* MIPI CSI-2 nodes */
csi_0 {
phys = <&video-phy 2>;
};
csi_1 {
phys = <&video-phy 3>;
};
I'm not sure if it is not an overkill to use this the PHY framework with
a device which has only 2 registers. Perhaps something less heavy could
be designed for it. However, if the PHY framework is commonly used there
should be no issue wrt enabling the whole big infrastructure for a simple
device like this.
Thanks,
Sylwester
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