Re: [PATCH v2 3/4] dt-bindings: Add pinctrl bindings for mt65xx/mt81xx.

On Tue, Sep 23, 2014 at 5:39 AM, Hongzhou.Yang
[off-list ref] wrote:

From: Hongzhou Yang <hongzhou.yang-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>

Add devicetree bindings for Mediatek SoC pinctrl driver.

Signed-off-by: Hongzhou Yang <hongzhou.yang-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>

I have worked on generic pin control bindings a bit because it
is getting out of hand with all these custom bindings.

See:
http://marc.info/?l=devicetree&m=141223584006648&w=2

Especially.

+- mediatek,pinfunc: List of gpio number and function to mux.

A "GPIO number" and a "pin number" is not the same thing at all,
this is very confusing. Those are two separate number spaces.
This is likely about the pin numbers.

+The mediatek,pinfunc can use defines directly,
+which are already defind in boot/dts/mt8135-pinfunc.h.
+
+Optional subnode-properties:
+- generic pin configuration option to use, bias-disable, bias-pull-down,
+  bias-pull,up, output-low and output-high are valid.
+  Example :
+       i2c0_pins_a {
+               mediatek,pinfunc = <MT8135_PIN_195_SDA1__FUNC_SDA1>;
+               bias-disable;
+       };

I don't like this approach at all.

I prefer that pins are put into groups named by strings, like "i2c0-pos0"
inside the driver and then connected to function with a certain
device-related name, such as "i2c0".

Then put the pin configuration (bias etc) in a separate node in the same
state definition like that:

i2c0_pins_a {
         function = "i2c0";
         groups = "i2c0-pos0";
};
i2c0_pins_b {
         bias-disable;
};

Yours,
Linus Walleij
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