ARM: Improve documentation in arm_timer.h

#ifndef __ASM_ARM_HARDWARE_ARM_TIMER_H

#define __ASM_ARM_HARDWARE_ARM_TIMER_H

#define TIMER_LOAD	0x00

#define TIMER_VALUE	0x04

#define TIMER_CTRL	0x08

#define TIMER_CTRL_ONESHOT	(1 << 0)

#define TIMER_CTRL_32BIT	(1 << 1)

#define TIMER_CTRL_DIV1		(0 << 2)

#define TIMER_CTRL_DIV16	(1 << 2)

#define TIMER_CTRL_DIV256	(2 << 2)

#define TIMER_CTRL_IE		(1 << 5)	/* Interrupt Enable (versatile only) */

#define TIMER_CTRL_PERIODIC	(1 << 6)

#define TIMER_CTRL_ENABLE	(1 << 7)

/*

 * ARM timer implementation, found in Integrator, Versatile and Realview

 * platforms.  Not all platforms support all registers and bits in these

 * registers, so we mark them with A for Integrator AP, C for Integrator

 * CP, V for Versatile and R for Realview.

 *

 * Integrator AP has 16-bit timers, Integrator CP, Versatile and Realview

 * can have 16-bit or 32-bit selectable via a bit in the control register.

 */

#define TIMER_LOAD	0x00			/* ACVR rw */

#define TIMER_VALUE	0x04			/* ACVR ro */

#define TIMER_CTRL	0x08			/* ACVR rw */

#define TIMER_CTRL_ONESHOT	(1 << 0)	/*  CVR */

#define TIMER_CTRL_32BIT	(1 << 1)	/*  CVR */

#define TIMER_CTRL_DIV1		(0 << 2)	/* ACVR */

#define TIMER_CTRL_DIV16	(1 << 2)	/* ACVR */

#define TIMER_CTRL_DIV256	(2 << 2)	/* ACVR */

#define TIMER_CTRL_IE		(1 << 5)	/*   VR */

#define TIMER_CTRL_PERIODIC	(1 << 6)	/* ACVR */

#define TIMER_CTRL_ENABLE	(1 << 7)	/* ACVR */

#define TIMER_INTCLR	0x0c

#define TIMER_RIS	0x10

#define TIMER_MIS	0x14

#define TIMER_BGLOAD	0x18

#define TIMER_INTCLR	0x0c			/* ACVR wo */

#define TIMER_RIS	0x10			/*  CVR ro */

#define TIMER_MIS	0x14			/*  CVR ro */

#define TIMER_BGLOAD	0x18			/*  CVR rw */

#endif