Clock Manager

Macros

CLOCK_MANAGER_OFFSET

This macro defines the offset at which the clock manager registers are located relative to the peripheral base. It has the value 0x101000

CLOCK_MANAGER_SIZE

This macro holds the size of the clock manager registers which needs to be mapped. It has the value 0xA4

CM_PASSWD

This macro holds the clock manager password. This value must always be present when writing to a clock manager register (e.g. by OR with the value). It has the value 0x5A000000

Registers

volatile uint32_t *clock_manager_base_ptr

This pointer points, when mapped, to the base of the clock manager registers.

struct clock_manager_register_map

This struct maps the registers of the clock manager. The names of the struct members correspond to the registers. Unfortunately, the official datasheet does not feature this chapter. But there is an upload of this chapter here: BCM2835 clocks:

struct clock_manager_register_map {
    uint32_t GP0CTL;
    uint32_t GP0DIV;
    uint32_t GP1CTL;
    uint32_t GP1DIV;
    uint32_t GP2CTL;
    uint32_t GP2DIV;
    uint32_t: 32;
    uint32_t: 32;
    uint32_t: 32;
    uint32_t: 32;
    uint32_t PCMCTL;
    uint32_t PCMDIV;
    uint32_t PWMCTL;
    uint32_t PWMDIV;
}

CM

#define CM ((volatile struct clock_manager_register_map *)(clock_manager_base_ptr + 28))

By using this macro, the registers of the clcok manager can be accessed like this CM->PWMCTL.

Enums

clock_source_t

This enum holds the values for the different clock sources:

typedef enum {
    CLOCK_GND,
    CLOCK_OSC,
    CLOCK_TST0,
    CLOCK_TST1,
    CLOCK_PLLA,
    CLOCK_PLLC,
    CLOCK_PLLD,
    CLOCK_HDMI
} clock_source_t;

Functions

uint32_t * clock_map(void)

This function maps the clock manager registers. It calls peripheral_map() with the values CLOCK_MANAGER_OFFSET and CLOCK_MANAGER_SIZE.

void clock_unmap(void)

This function unmaps the clock manager.

The following functions all take a pointer to a clock manager register as an argument because all the registers for the different clocks have the same structure. This means that you just need to tell the clock manager which clock to use (by pointing to the right register). For example: clock_enable(&CM->PWMCTL);

void clock_enable(volatile uint32_t *reg)

This function enables the clock with the register pointed to by reg.

void clock_disable(volatile uint32_t *reg)

This function disables the clock with the register pointed to by reg.

void clock_configure(volatile uint32_t *reg, clock_source_t src, unsigned int divisor, unsigned int mash)

This function configures the clock with the register pointed to by reg and sets up the clock_source_t src, the divisor divisor with the mash factor mash.

Todo

Add a decimal places to the divisor.