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    SubjectRe: [PATCH 07/10] pinctrl: add pinctrl driver for Rockchip SoCs
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    On Tue, Jun 4, 2013 at 2:05 PM, Heiko Stübner <heiko@sntech.de> wrote:

    >> > +PULL_AUTO (1 << 0): indicate this pin needs a pull setting for SoCs
    >> > + that determine the pull up or down themselfs
    >>
    >> Hm, never saw that before...
    >
    > Citing the original gpio driver:
    >
    > /*
    > * Values written to this register independently
    > * control Pullup/Pulldown or not for the
    > * corresponding data bit in GPIO.
    > * 0: pull up/down enable, PAD type will decide
    > * to be up or down, not related with this value
    > * 1: pull up/down disable
    > */
    >
    > So if it's a pull up or down is decided based on the mux of the pin. Calling
    > everything a "pull down" (or up) when it isn't seemed somehow wrong to me.
    >
    > The rk3188 on the other hand supports both pull up and down separately.
    >
    > Or should this be selected as PULL_UP | PULL_DOWN in the config?

    The generic config is pretty much either/or so it'd be a new
    config for that approach.

    Basically it seems they have embedded knowledge into the
    silicon: there is no specific rule as to whether a pad should be
    pulled up or down depending on "pad type" as is stated, rather
    it's so that if you know a pad will be used for I2C SCL then
    you know it needs pull-up. Probably something like a "1" on
    some constant switch in VHDL/Verilog is hard-coded into
    the silicon turning on pull-up if I2C is selected and the
    autopull is set for example.

    >> +config PINCTRL_ROCKCHIP
    >> + bool
    >> + select PINMUX
    >> + select PINCONF
    >> + select GENERIC_IRQ_CHIP
    >>
    >> Why is this super-simple pin config thing not using
    >> GENERIC_PINCONF?
    >>
    >> I *know* it is simpler to implement your own thing, but think of the
    >> poor maintainers that have to wade through 50 identical implementations.
    >> Do this, it pays off.
    >
    > generic pinconf sounds interesting ... will give it a try.
    >
    > The only problem is the pull stuff mentioned above that is either pull up or
    > down without the driver having knowledge about it. And generic_pinconf only
    > knows about them separately right now.

    Create a separate patch adding PIN_CONFIG_BIAS_PULL_AUTO
    to include/linux/pinctrl/pinconf-generic.h, don't forget the
    kerneldoc, and patching drivers/pinctrl/pinconf-generic.c.

    I'll apply it right away.

    >> Nothing else you want to say about the pins here?
    >> (No big deal for sure, but....)
    >
    > when using pinconfig_generic, its dump_pin function should be more talkative
    > right?

    Yes, one of the things you get for free... soon also the pin config
    DT parser will be for free I hope.

    Yours,
    Linus Walleij
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