UM0851 datasheet(27/245 Pages) STMICROELECTRONICS

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UM0851

Platform section

Doc ID 16604 Rev 2

27/245

Figure 3.

GPT software architecture

In the Linux source tree, the GPT layer is present in arch/arm/plat-spear/gpt.c

GPT layer interface

The GPT layer represents the timer as a structure with the following fields.

struct spear_timer {

unsigned long phys_base;

int irq;

struct clk *iclk; /* interface clk */

struct clk *fclk; /* functional clk */

void __iomem *io_base;

unsigned reserved:1;

unsigned enabled:1;

};

The SPEAr LSP defines an array (of struct spear_timer) for the available timers on each

respective platform. The GPT layer provides a set of APIs which operate on this structure to

manage the set of available timers.

Allocating a timer

There are two ways of allocating a GPT. You can either ask for a free timer, in this case an

available timer on the list will be allocated to you, or, ask for a specific timer, so if it is

available, it will be allocated to you. Both the APIs return one of the available timers (or

NULL), which you can subsequently use to program and control the timer.

/* request for a free timer */

struct spear_timer *spear_timer_request(void);

/* request for a specific timer greater than or equal to 1 */

struct spear_timer *spear_timer_request_specific(int timer);

UM0851 데이터시트(PDF) 27 Page - STMicroelectronics