blob: a5bf961a077d271cbb3acfb53392cc90bf409627 [file] [log] [blame]
/*
* Copyright (c) 2008 Travis Geiselbrecht
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
.globl init_48mhz_clock
#define PMC_MCKR 0x30
#define PMC_SR 0x68
#define PMC_MCKRDY 0x08
#define PMC_PRES_DIV2 0x04
#define PMC_CSS_PLL 0x03
/* BUG?
**
** If I try to exit by bx lr, lr is corrupted somewhere in here.
** No clue why. FIQ USB wedge not playing nice? Am I cheating
** with my CPSR calls?
*/
init_48mhz_clock:
ldr r1, =0xfffffc00
mov r2, lr
// turn on /2 prescaler
mov r0, #PMC_PRES_DIV2
str r0, [r1, #PMC_MCKR]
wait_for_clock1:
ldr r0, [r1, #PMC_SR]
tst r0, #PMC_MCKRDY
beq wait_for_clock1
// switch to pll clock
mov r0, #(PMC_PRES_DIV2 | PMC_CSS_PLL)
str r0, [r1, #PMC_MCKR]
wait_for_clock2:
ldr r0, [r1, #PMC_SR]
tst r0, #PMC_MCKRDY
beq wait_for_clock2
bx r2