Subversion Repositories c0or1k

/*

 * CPU cycles per timer tick

 *

 * Copyright (C) 2010 B Labs Ltd.

 *

 * Author: Bahadir Balban

 */

#define CPUOP_NOOP      0

#define CPUOP_MEMORY    1

#include INC_ARCH(asm.h)

        .section .text

/*

 * Default:

 * Go for 1000 CPU cycles on no ops and calculate

 * how many timer ticks it takes.

 *

 * By default timer is expected to tick per 1/1,000,000 second,

 * has been preloaded, and initialized for enabling. All we do

 * here is enable it, do our ops and read back the counter

 * difference.

 *

 * r0 = timer enable address

 * r1 = timer value address

 * r2 = op type

 * r3 = op count

 * return = how many timer ticks

 */

BEGIN_PROC(cpu_do_cycles_and_tick)

        stmfd sp!, {r4, lr}     @ Make room for new data in r4-5

        ldr r4, [r1]            @ Load timer value to r5

        str r2, [r0]            @ Start the timer.

1:

        subs r3, r3, #1         @ Decrement count

        bhi 1b

finish:

        ldr r0, [r1, #4]        @ Load current value, from load register + 4

        sub r0, r4, r0          @ Return difference between original and read

        ldmfd sp!, {r4, pc}     @ Restore R4-R5, pc

BEGIN_PROC(busy_loop)

        subs r0, r0, #1

        bhi busy_loop

        mov pc, lr

END_PROC(busy_loop)