On 02.03.2015 21:01, Stephen Warren wrote:
On 02/27/2015 05:24 AM, Sebastian Hesselbarth wrote:
I2C mux pinctrl driver currently determines the number of sub-busses by
counting available pinctrl-names. Unfortunately, this requires each
incarnation of the devicetree node with different available sub-busses
to be rewritten.
This patch reworks i2c-mux-pinctrl driver to count the number of
available sub-nodes instead. The rework should be compatible to the old
way of probing for sub-busses and additionally allows to disable unused
sub-busses with standard DT property status = "disabled".
This also amends the corresponding devicetree binding documentation to
reflect the new functionality to disable unused sub-nodes. While at it,
also fix two references to binding documentation files that miss an
"i2c-"
prefix.
diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
-For each named state defined in the pinctrl-names property, an I2C
child bus
-will be created. I2C child bus numbers are assigned based on the
index into
-the pinctrl-names property.
+For each enabled child node an I2C child bus will be created. I2C
child bus
+numbers are assigned based on the order of child nodes.
I think that I2C bus numbers are an internal concept for the OS. As
such, we should probably remove any mention re: the bus numbers from the
binding.
Stephen,
yeah as you can see I am struggling to find a good documentation. I
agree that we should get rid of the bus number thing above.
-The only exception is that no bus will be created for a state named
"idle". If
-such a state is defined, it must be the last entry in pinctrl-names. For
-example:
+There must be a corresponding pinctrl-names entry for each enabled child
+node at the position of the child node's "reg" property. Also, there
can be
+an idle pinctrl state defined at the end of possible pinctrl states.
If such
+a state is defined, it must be the last entry in pinctrl-names. For
example:
What about gaps in the numbering sequence? IIRC, in a situation with 5
nodes with reg 0, 1, 2, 3, 4 but where only the nodes with reg of 1, 3
enabled, we only want 2 entries in pinctrl-names? If so, "at the
position of the child node's "reg" property" isn't correct, since "at
the position" implies there must be gaps in pinctrl-names. "In the same
order as the reg property values for enabled subnodes" might be a better
description.
Good point. The idea was to _have_ gaps in pinctrl-names to allow to
configure the current mux layout by status properties only. The existing
implementation (and docu) suggested you have to amend pinctrl-names to
achieve a specific setup.
Perhaps I'm misremembering and you explicitly didn't want to remove
entries from pinctrl-names if child nodes were disabled? If so, then
surely then in the text above, "for each enabled child" should be
replaced with "for each child"?
True.
@@ -68,6 +68,7 @@ Example:
pinctrl-1 = <&state_i2cmux_pta>;
pinctrl-2 = <&state_i2cmux_idle>;
+ /* Enabled child bus 0 */
i2c@0 {
reg = <0>;
#address-cells = <1>;
@@ -79,10 +80,12 @@ Example:
};
};
+ /* Disabled child bus 1 */
i2c@1 {
reg = <1>;
#address-cells = <1>;
#size-cells = <0>;
+ status = "disabled";
To make the example cover more cases, perhaps make child node i2c@0
disabled and i2c@1 enabled. Then, the example would show what happens to
pinctrl-names when there are gaps in the reg property numbering space of
enabled children?
The idea was to make nothing happen to pinctrl-names if you enable/
disable any of the children. But I can move the disabled status to
i2c@0 to make it more clear that there should still be a pinctrl-names
cell for it.
Sebastian
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