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    SubjectRe: [RFC,PATCH 1/3] Add a common struct clk
    Hello,

    On Thu, Feb 10, 2011 at 06:03:19PM +0800, Richard Zhao wrote:
    > On Thu, Feb 10, 2011 at 09:21:14AM +1300, Ryan Mallon wrote:
    > > On 02/09/2011 07:41 PM, Jeremy Kerr wrote:
    > >
    > > Hi Jeremy,
    > >
    > > Couple more comments below.
    > >
    > > ~Ryan
    > >
    > [...]
    > > > +int clk_enable(struct clk *clk)
    > > > +{
    > > > + unsigned long flags;
    > > > + int ret = 0;
    > > > +
    > > > + spin_lock_irqsave(&clk->enable_lock, flags);
    > >
    > > WARN_ON(clk->prepare_count == 0); ?
    > >
    > > > + if (clk->enable_count == 0 && clk->ops->enable)
    > > > + ret = clk->ops->enable(clk);
    > >
    > > Does it make sense to have a clock with no enable function which still
    > > returns success from clk_enable? Do we have any platforms which have
    > > NULL clk_enable functions?
    > >
    > > I think that for enable/disable at least we should require platforms to
    > > provide functions and oops if they have failed to do so. In the rare
    > > case that a platform doesn't need to do anything for enable/disable they
    > > can just supply empty functions.
    > It's possible to be NULL. So are set_rate/get_rate.
    > Ideally, if it's NULL:
    > prepare/unprepare: only call parent's prepare/unprepare
    > enable/disable: only call parent's enable/disable
    > set_rate: fail
    > get_rate: reture parent's get_rate
    > set_parent: fail
    > get_parent: fail
    I wouldn't hard-code the parents into the generic functions. But I
    suggest to provide generic callbacks to do this, e.g.

    clk_get_rate_from_parent(struct clk *c)
    {
    struct clk *parent = clk_get_parent(c);

    return clk_get_rate(parent);
    }

    Best regards
    Uwe

    --
    Pengutronix e.K. | Uwe Kleine-König |
    Industrial Linux Solutions | http://www.pengutronix.de/ |
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