[RFC,PATCH 1/2] Add a common struct clk
Jeremy Kerr
jeremy.kerr at canonical.com
Thu Sep 9 22:10:55 EDT 2010
Hi Ben,
> > > > +#define INIT_CLK(name, o) \
> > > > + { .ops = &o, .enable_count = 0, \
> > > > + .mutex = __MUTEX_INITIALIZER(name.mutex) }
> > >
> > > how about doing the mutex initinitialisation at registration
> > > time, will save a pile of non-zero code in the image to mess up
> > > the compression.
> >
> > I've just yesterday added the following to my tree, to allow dynamic
> > initialisation:
> >
> > static inline void clk_init(struct clk *clk, const struct clk_ops *ops)
> > {
> > clk->ops = ops;
> > clk->enable_count = 0;
> > mutex_init(&clk->mutex);
> > }
> >
> > So we can do this either way.
>
> the above is in my view better.
After implementing this, it turns out it won't work - we don't have
access to all clocks in order to do the mutex init (thanks to Jason Hui
for pointing this out).
At present, I'm calling clk_init_common() (which initialises the mutex)
from clkdev_add, but there are clocks that don't get initialised. For
example:
struct clk_fixed parent_clk = INIT_CLK(32768);
struct clk_foo child_clk = INIT_CLK_FOO(parent.clk);
struct clk_lookup lookup = {
.dev_id = "foo",
.clk = child_clk,
};
function platform_clk_init(void)
{
clkdev_add(lookup);
}
In this case, the child_clk's mutex will get initialised, but
parent_clk's won't. We can't walk the parents of child_clk and
initialise, as we may re-initialise the mutexes of parents with > 1
child.
Now, we *could* do the clk_common_init() from board-specific code, and
require that that code guarantees to call clk_common_init() on every
clock defined. I think that's a recipe for pain, as there will
undoubtedly be clocks missed, causing an oops when the clock is first
used.
So I think the solution will have to be to do the mutex initialisation
statically. I'm planning to leave clk_common_init() available for clocks
initalised at runtime, but it will no longer be called automatically
from core code.
Any thoughts?
Cheers,
Jeremy
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