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