UM0851 datasheet(229/245 Pages) STMICROELECTRONICS

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UM0851

Power management section

Doc ID 16604 Rev 2

229/245

Figure 68.

Clock framework architecture

The interaction with the kernel and the architecture specific code can be subdivided into

three parts: kernel, middle level clock management layer and low level clock management

layer (see Figure 68).

Kernel interaction

Whenever the device drivers need some functionality that involves the interaction with the

clock framework, Linux provides the following APIs defined in the Linux Clock framework.

struct clk* clk_get /* lookup and obtain a reference to a clock producer */

struct clk*

clk_enable /* inform the system when the clock source should be running

struct clk*

clk_disable /* inform the system when the clock source is no longer

required */

struct clk*

clk_put: /* free

the clock source */

struct clk*

clk_get_rate /* obtain the current clock rate (in Hz) for a clock

source. */

struct clk*

clk_set_rate /* set the clock rate for a clock source */

User application

Kernel device driver

Middle level clock management

(arch/arm/plat-spear/clock.c)

Low level clock management

(arch/arm/mach-spearxxx/spearxxx_clock.c)

clk_enable

clk_disable

clk_get

clk_get_rate

clk_put

Kernel

space

User

space

Hardware

Hardware clock generating unit

Reference count

Dependency resolving

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