On Thu, Sep 22, 2011 at 03:26:56PM -0700, Mike Turquette wrote:
> From: Jeremy Kerr <jeremy.k...@canonical.com>
>
> We currently have ~21 definitions of struct clk in the ARM architecture,
> each defined on a per-platform basis. This makes it difficult to define
> platform- (or architecture-) independent clock sources without making
> assumptions about struct clk, and impossible to compile two
> platforms with different struct clks into a single image.
>
> This change is an effort to unify struct clk where possible, by defining
> a common struct clk, and a set of clock operations. Different clock
> implementations can set their own operations, and have a standard
> interface for generic code. The callback interface is exposed to the
> kernel proper, while the clock implementations only need to be seen by
> the platform internals.
>
> The interface is split into two halves:
>
> * struct clk, which is the generic-device-driver interface. This
> provides a set of functions which drivers may use to request
> enable/disable, query or manipulate in a hardware-independent manner.
>
> * struct clk_hw and struct clk_hw_ops, which is the hardware-specific
> interface. Clock drivers implement the ops, which allow the core
> clock code to implement the generic 'struct clk' API.
>
> This allows us to share clock code among platforms, and makes it
> possible to dynamically create clock devices in platform-independent
> code.
>
> Platforms can enable the generic struct clock through
> CONFIG_GENERIC_CLK. In this case, the clock infrastructure consists of a
> common, opaque struct clk, and a set of clock operations (defined per
> type of clock):
>
> struct clk_hw_ops {
> int (*prepare)(struct clk_hw *);
> void (*unprepare)(struct clk_hw *);
> int (*enable)(struct clk_hw *);
> void (*disable)(struct clk_hw *);
> unsigned long (*recalc_rate)(struct clk_hw *);
> int (*set_rate)(struct clk_hw *,
> unsigned long, unsigned long *);
> long (*round_rate)(struct clk_hw *, unsigned long);
> int (*set_parent)(struct clk_hw *, struct clk *);
> struct clk * (*get_parent)(struct clk_hw *);
> };
>
> Platform clock code can register a clock through clk_register, passing a
> set of operations, and a pointer to hardware-specific data:
>
> struct clk_hw_foo {
> struct clk_hw clk;
> void __iomem *enable_reg;
> };
>
> #define to_clk_foo(c) offsetof(c, clk_hw_foo, clk)
>
> static int clk_foo_enable(struct clk_hw *clk)
> {
> struct clk_foo *foo = to_clk_foo(clk);
> raw_writeb(foo->enable_reg, 1);
> return 0;
> }
>
> struct clk_hw_ops clk_foo_ops = {
> .enable = clk_foo_enable,
> };
>
> And in the platform initialisation code:
>
> struct clk_foo my_clk_foo;
>
> void init_clocks(void)
> {
> my_clk_foo.enable_reg = ioremap(...);
>
> clk_register(&clk_foo_ops, &my_clk_foo, NULL);
Shouldn't this be:
clk_register(&clk_foo_ops, &my_clk_foo->clk, NULL);
?
Also, this documentation would be good to have in the Documentation
directory instead of lost in a commit header.
Otherwise looks okay to me.
Reviewed-by: Grant Likely <grant.lik...@secretlab.ca>
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