[RFC,PATCH 1/2] Add a common struct clk
Russell King - ARM Linux
linux at arm.linux.org.uk
Thu Jun 3 07:05:33 EDT 2010
On Thu, Jun 03, 2010 at 06:24:50PM +0800, Jeremy Kerr wrote:
> OK, this would mean adding parent to struct clk:
>
> struct clk {
> struct clk_operations *ops;
> atomic_t enable_count;
I don't think it makes sense for this to be an atomic type.
> static inline int clk_enable(struct clk *clk)
> {
> int ret;
>
> if (atomic_inc(clk->enable_count) != 1))
> return 0;
Okay, so what if we sleep at this point, and someone else comes along
and calls clk_enable(), which'll merely increment the count and return.
Unfortunately, the clock is still disabled at that point - which is a
violation of what's supposed to happen.
Or to put it another way, the above method results in clk_enable()
sometimes returning with the clock enabled and sometimes with the
clock still disabled.
That's not nice behaviour for drivers which may need the clock enabled
to read/write the device registers.
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