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    SubjectRe: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux mappings
    On Sun, Jan 08, 2012 at 08:51:59PM +0800, Richard Zhao wrote:
    > > > So, this does appear to be conflating the two things: The definition of
    > > > what pins are in a pingroup, and the mux function for a particular
    > > > setting of that pingroup. I think you need separate nodes for this.
    > > >
    > > At least for imx, we do not have mux function setting for pingroup.
    > > Instead, it only applies to individual pin.
    > I think it depends on function definition of pinmux driver. For the
    > imx example patch, it's one-to-one.

    It should depend on particular imx soc pinmux design rather than
    pinmux driver. If it's always one-to-one case, we do not need
    pinmux at all. Aisheng's patch just did not enumerate all the groups
    for given function. Instead, it puts a couple simple examples there
    for demonstration.


    > > > uart4func: func@1 {
    > > > func-name = "uart4";
    > > > locations = <&bargrp &bazgrp>;
    > > > mux-value = <6 3>;
    > > > };
    > >
    > > I prefer to have function node defined in <board>.dtsi, since it's
    > > all about defining phandle to the correct pingroup, which should be
    > > decided by board design.
    > group and function are one-to-one mapped for imx.

    Again, it's not the case.

    > So if you put function
    > in board dts, why not put pin group there too?

    If we put pingroup data in <board>.dts, the data will be likely get
    duplicated a lot in different board dts files. For example, if
    imx6q-sabrelite chooses the same pingroup for usdhc3 and usdhc4 as
    imx6q-arm2, the pingroup data will be duplicated between imx6q-arm2.dts
    and imx6q-sabrelite.dts.

    On the contrary, putting pingroup data in <soc>.dtsi and having function
    node in <board>.dts with phandle pointing to the correct pingroup will
    help avoid such data duplication.


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