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    SubjectRe: [PATCH v7 2/3] clk: introduce the common clock framework
    On Tue, Mar 20, 2012 at 10:46 AM, Saravana Kannan
    <> wrote:
    > On Tue, March 20, 2012 7:02 am, Shawn Guo wrote:
    >> On Thu, Mar 15, 2012 at 11:11:19PM -0700, Mike Turquette wrote:
    >> ...
    >>> +struct clk_ops {
    >>> +    int             (*prepare)(struct clk_hw *hw);
    >>> +    void            (*unprepare)(struct clk_hw *hw);
    >>> +    int             (*enable)(struct clk_hw *hw);
    >>> +    void            (*disable)(struct clk_hw *hw);
    >>> +    int             (*is_enabled)(struct clk_hw *hw);
    >>> +    unsigned long   (*recalc_rate)(struct clk_hw *hw,
    >>> +                                    unsigned long parent_rate);
    >> I believe I have heard people love the interface with parent_rate
    >> passed in.  I love that too.  But I would like to ask the same thing
    >> on .round_rate and .set_rate as well for the same reason why we have
    >> it for .recalc_rate.
    > In my case, for most clocks, set rate involves reparenting. So, what does
    > passing parent_rate for these even mean? Passing parent_rate seems more
    > apt for recalc_rate since it's called when the parent rate changes -- so,
    > the actual parent itself is not expected to change.

    From my conversations with folks across many platforms, I think that
    the way your clock tree expects to change rates is the exception, not
    the rule. As such you should just ignore the parent_rate parameter as
    it useless to you.

    > I could ignore the parameter, but just wondering how many of the others
    > see value in this. And if we do add this parameter, it shouldn't be made
    > mandatory for the platform driver to use it (due to other assumptions the
    > clock framework might make).

    From my rough census of folks that actually need .set_rate support, I
    think that everyone except MSM could benefit from this. Your concept
    of clk_set_rate is everyone else's clk_set_parent.

    Ignoring the new parameter should cause you no harm. It does make me
    wonder if it would be a good idea to pass in the parent rate for
    .set_parent, which is analogous to .set_rate in many ways.


    > -Saravana
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