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    SubjectRE: [PATCH] pinctrl: make the pinmux-pins more helpful
    Linus Walleij wrote at Wednesday, February 29, 2012 2:39 AM:
    > On Fri, Feb 24, 2012 at 5:44 PM, Stephen Warren <swarren@nvidia.com> wrote:
    >
    > > If we do make a change like this, I'd prefer the format to be:
    > >
    > > UNCLAIMED
    > > "%s (HOG)", desc->owner
    > > desc->owner
    >
    > I don't see the point, the debugfs files are supposed to be
    > human-readable, a human is not interested in the fact that
    > the pinctrl device itself is owning the pin, what is interesting is
    > that it is hogged.

    Well, I'm a human and I care far more that the pin controller device is
    what owns the configuration rather than some artificial "hog" concept
    is present...

    > >> I somewhat mourn the loss of being able to tell from the debugfs
    > >> which function is using a certain pin, does anyone have ideas on
    > >> how to go about fixing this properly? The root file
    > >> pinctrl-handles does tell it, but requires cross-referencing
    > >> which isn't helpful.
    > >
    > > This doesn't seem like a big deal to me; it's very easy to cross-
    > > reference.
    >
    > Not to me it isn't, looks like I would have to create scripts to
    > do that for a large pin controller and that's less helpful than
    > just having the information there.
    >
    > > That said, we could either:
    > >
    > > a) Add a field to pin_desc which indicates current usage. This would be
    > > set whenever the pin's mux function was set, i.e. in pinctrl_select_state()
    > > or pinctrl_request_gpio().
    >
    > That's like re-introducing the former "function" field I guess.
    >
    > Simple if I just also #ifdef CONFIG_DEBUGFS... so I'd go
    > for this.
    >
    > > b) Add a pinctrl driver ops function which reads and prints the current
    > > state from HW.
    > >
    > > (and note the fact that having the debug file list the current mux
    > > function per pin doesn't really make sense on HW where the muxing is
    > > per group...)
    >
    > On U300 it makes a lot of sense even thogh it is essentially
    > group based. When sitting with the datasheet with the pin names
    > and use groups it's simple to see exactly how any one pin is muxed
    > for the moment and troubleshoot from there.

    If the HW muxes per group, then there's no concept of "which function is
    selected for a pin", since functions are selected for a group not for a
    pin.

    So, the datasheet will be written in terms of "group X supports functions
    A, B, C, D", not pins P, Q, R support functions "A, B, C, D". So,
    representing mux function in debugfs at the group level would make a lot
    more sense given that HW design.

    --
    nvpublic



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