How to describe I2C and MDIO bus multiplexers with the device tree?
From: David Daney
Date: Wed Aug 03 2011 - 18:04:39 EST
I have a board (ASCII art representation below) that has a bunch of
PHY devices that are connected behind a MDIO bus switch/multiplexer.
This multiplexer is in turn controlled by GPIO pins on a I2C GPIO port
expander. which is in turn on a I2C bus switch/multiplexer.
There is another switch/multiplexer that is controlled directly via I2C.
Q: How can this be represented?
My attempt is below...
I2C-0
MDIO-1 MDIO-0
|
| |
| |--------------|
| |
| | +---- I2C-A -----
| |
+---------+ multiplexor |
| |
| | +---- I2C-B -----
| |
| | I2C-0x70 |
| |
| | +---- I2C-C -----
| |
| | |
| |
| | +---- I2C-D -----
| |
| | |
| |
| | +---- I2C-E -----
| |
| | |
| |
| | +---- I2C-F --------+
| |
| | | |
| |
| | +---- I2C-G --+ |
| |
| |--------------| | |
| |
| | |
| |
| |------------| +-----+ |
| |
| | | | |
| |
+--------+ ds1337 RTC| | |
| |
| | I2C-0x68 | | |-----+-----|
|--------+---------| |
| |------------| | | GPIO | |
| |
| | | Port +--Pin 3---+
multiplexor | |
| | | Expander +--Pin 4---+
| |
| | | | |
74CBTLV3253 | |
| | |I2C-0x38 | |
| |
| | | | |
| |
| | |-----------|
|-+--------------+-| |
| | |
| |
| | |
| |
| |----+-----| M
M |
| | GPIO | D
D |
| | Port | I
I |
| | Expander | O
O |
| | | |
| |
| |I2C-0x38 | W
X |
| |----------| |
| |
| |
| |
| |
| |
|
|----+---| |----+---| |
| |
| | | |
| | PHY-11
| | PHY-21 | |
| | PHY-12
| | PHY-22 | |
| | PHY-13
| | PHY-23 | |
| | PHY-14
| | PHY-24 | |
|
|--------| |--------| |
|
|
| |-------------|
|
| | multiplexor |
|
| | I2C-0x77
+----------------------------------------------------------------+
+---------+ foo |
| | |
| |-+--------+--|
| | |
| |
M M
D D
I I
O O
| |
Y Z
| |
|-----+--| |--+----|
| PHY-3 | | PHY-4 |
|--------| |-------|
/dts-v1/;
/ {
model = "cavium,brfl";
compatible = "cavium,brfl";
#address-cells = <2>;
#size-cells = <2>;
interrupt-parent = <&ciu>;
soc@0 {
.
.
.
smi0: mdio@1180000001800 {
compatible = "cavium,octeon-3860-mdio";
#address-cells = <1>;
#size-cells = <0>;
reg = <0x11800 0x00001800 0x0 0x40>;
};
smi1: mdio@1180000001900 {
compatible = "cavium,octeon-3860-mdio";
#address-cells = <1>;
#size-cells = <0>;
reg = <0x11800 0x00001900 0x0 0x40>;
};
.
.
.
twsi0: i2c@1180000001000 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "cavium,octeon-3860-twsi";
reg = <0x11800 0x00001000 0x0 0x200>;
interrupts = <0 45>;
clock-rate = <100000>;
.
.
.
i2c-mux@70 {
compatible = "nxp,pca9548";
reg = <0x38>;
i2c@6 {
#address-cells = <1>;
#size-cells = <0>;
cell-index = <6>;
gpio66: gpio@38 {
compatible = "nxp,pca8574";
reg = <0x38>;
#gpio-cells = <2>;
gpio-controller;
};
}
};
.
.
.
mdio-mux@77 {
compatible = "bar,foo";
reg = <0x77>;
parent-bus = <&smi0>
#address-cells = <1>;
#size-cells = <0>;
mdio@0 {
#address-cells = <1>;
#size-cells = <0>;
cell-index = <0>;
phy3: ethernet-phy@1 {
reg = <1>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
mdio@1 {
#address-cells = <1>;
#size-cells = <0>;
cell-index = <1>;
phy4: ethernet-phy@1 {
reg = <1>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
};
.
.
.
};
mdio-mux@0 {
compatible = "ti,sn74cbtlv3253"
gpios = <&gpio66 3 1
&gpio66 4 1>
parent-bus = <&smi1>
#address-cells = <1>;
#size-cells = <0>;
mdio@2 {
#address-cells = <1>;
#size-cells = <0>;
cell-index = <2>;
phy11: ethernet-phy@1 {
reg = <1>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy12: ethernet-phy@1 {
reg = <2>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy13: ethernet-phy@1 {
reg = <3>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy14: ethernet-phy@1 {
reg = <4>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
};
mdio@3 {
#address-cells = <1>;
#size-cells = <0>;
cell-index = <3>;
phy21: ethernet-phy@1 {
reg = <1>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy22: ethernet-phy@1 {
reg = <2>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy23: ethernet-phy@1 {
reg = <3>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
phy24: ethernet-phy@1 {
reg = <4>;
compatible = "marvell,88e1149r";
marvell,reg-init = <3 0x10 0 0x5777>,
<3 0x11 0 0x00aa>,
<3 0x12 0 0x4105>,
<3 0x13 0 0x0a60>;
};
};
};
.
.
.
};
};
Some notes/questions:
o mdio-mux@0 is a child of soc@0, but conceptually it might just as
well be floating in space.
o The parent-bus property of both mdio-mux@0 and mdio-mux@77 denotes
the connection of the multiplexer to its 'parent' bus.
o The cell-index property of the multiplexed bus instances denotes the
sub-bus of the switch/multiplexer the children are connected to.
Would a different property name be better here?
o For mdio-mux@0 the driver will use the cell-index to determine how
to program the gpios that control the switch/multiplexer.
Am I totally insane?
David Daney
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