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/*
* U-boot - start.S Startup file for Blackfin u-boot
*
* Copyright (c) 2005-2008 Analog Devices Inc.
*
* This file is based on head.S
* Copyright (c) 2003 Metrowerks/Motorola
* Copyright (C) 1998 D. Jeff Dionne <jeff@ryeham.ee.ryerson.ca>,
* Kenneth Albanowski <kjahds@kjahds.com>,
* The Silver Hammer Group, Ltd.
* (c) 1995, Dionne & Associates
* (c) 1995, DKG Display Tech.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
* MA 02110-1301 USA
*/
#include <config.h>
#include <asm/blackfin.h>
#include <asm/mach-common/bits/core.h>
#include <asm/mach-common/bits/dma.h>
#include <asm/mach-common/bits/pll.h>
#include "serial.h"
/* It may seem odd that we make calls to functions even though we haven't
* relocated ourselves yet out of {flash,ram,wherever}. This is OK because
* the "call" instruction in the Blackfin architecture is actually PC
* relative. So we can call functions all we want and not worry about them
* not being relocated yet.
*/
.text
ENTRY(_start)
/* Set our initial stack to L1 scratch space */
sp.l = LO(L1_SRAM_SCRATCH_END - 20);
sp.h = HI(L1_SRAM_SCRATCH_END - 20);
#ifdef CONFIG_HW_WATCHDOG
# ifndef CONFIG_HW_WATCHDOG_TIMEOUT_START
# define CONFIG_HW_WATCHDOG_TIMEOUT_START 5000
# endif
/* Program the watchdog with an initial timeout of ~5 seconds.
* That should be long enough to bootstrap ourselves up and
* then the common u-boot code can take over.
*/
P0.L = LO(WDOG_CNT);
P0.H = HI(WDOG_CNT);
R0.L = 0;
R0.H = HI(MSEC_TO_SCLK(CONFIG_HW_WATCHDOG_TIMEOUT_START));
[P0] = R0;
/* fire up the watchdog - R0.L above needs to be 0x0000 */
W[P0 + (WDOG_CTL - WDOG_CNT)] = R0;
#endif
/* Turn on the serial for debugging the init process */
serial_early_init
serial_early_set_baud
serial_early_puts("Init Registers");
/* Disable self-nested interrupts and enable CYCLES for udelay() */
R0 = CCEN | 0x30;
SYSCFG = R0;
/* Zero out registers required by Blackfin ABI.
* http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
*/
r1 = 0 (x);
/* Disable circular buffers */
l0 = r1;
l1 = r1;
l2 = r1;
l3 = r1;
/* Disable hardware loops in case we were started by 'go' */
lc0 = r1;
lc1 = r1;
/* Save RETX so we can pass it while booting Linux */
r7 = RETX;
/* Figure out where we are currently executing so that we can decide
* how to best reprogram and relocate things. We'll pass below:
* R4: load address of _start
* R5: current (not load) address of _start
*/
serial_early_puts("Find ourselves");
call _get_pc;
.Loffset:
r1.l = .Loffset;
r1.h = .Loffset;
r4.l = _start;
r4.h = _start;
r3 = r1 - r4;
r5 = r0 - r3;
/* Inform upper layers if we had to do the relocation ourselves.
* This allows us to detect whether we were loaded by 'go 0x1000'
* or by the bootrom from an LDR. "R6" is "loaded_from_ldr".
*/
r6 = 1 (x);
cc = r4 == r5;
if cc jump .Lnorelocate;
r6 = 0 (x);
/* In bypass mode, we don't have an LDR with an init block
* so we need to explicitly call it ourselves. This will
* reprogram our clocks, memory, and setup our async banks.
*/
serial_early_puts("Program Clocks");
/* if we're executing >=0x20000000, then we dont need to dma */
r3 = 0x0;
r3.h = 0x2000;
cc = r5 < r3 (iu);
if cc jump .Ldma_and_reprogram;
r0 = 0 (x); /* set bootstruct to NULL */
call _initcode;
jump .Lprogrammed;
/* we're sitting in external memory, so dma into L1 and reprogram */
.Ldma_and_reprogram:
r0.l = LO(L1_INST_SRAM);
r0.h = HI(L1_INST_SRAM);
r1.l = __initcode_lma;
r1.h = __initcode_lma;
r2.l = __initcode_len;
r2.h = __initcode_len;
r1 = r1 - r4; /* convert r1 from load address of initcode ... */
r1 = r1 + r5; /* ... to current (not load) address of initcode */
p3 = r0;
call _dma_memcpy_nocache;
r0 = 0 (x); /* set bootstruct to NULL */
call (p3);
/* Since we reprogrammed SCLK, we need to update the serial divisor */
.Lprogrammed:
serial_early_set_baud
/* Relocate from wherever we are (FLASH/RAM/etc...) to the hardcoded
* monitor location in the end of RAM. We know that memcpy() only
* uses registers, so it is safe to call here. Note that this only
* copies to external memory ... we do not start executing out of
* it yet (see "lower to 15" below).
*/
serial_early_puts("Relocate");
r0 = r4;
r1 = r5;
r2.l = LO(CONFIG_SYS_MONITOR_LEN);
r2.h = HI(CONFIG_SYS_MONITOR_LEN);
call _memcpy_ASM;
/* Initialize BSS section ... we know that memset() does not
* use the BSS, so it is safe to call here. The bootrom LDR
* takes care of clearing things for us.
*/
serial_early_puts("Zero BSS");
r0.l = __bss_vma;
r0.h = __bss_vma;
r1 = 0 (x);
r2.l = __bss_len;
r2.h = __bss_len;
call _memset;
.Lnorelocate:
/* Setup the actual stack in external memory */
sp.h = HI(CONFIG_STACKBASE);
sp.l = LO(CONFIG_STACKBASE);
fp = sp;
/* Now lower ourselves from the highest interrupt level to
* the lowest. We do this by masking all interrupts but 15,
* setting the 15 handler to ".Lenable_nested", raising the 15
* interrupt, and then returning from the highest interrupt
* level to the dummy "jump" until the interrupt controller
* services the pending 15 interrupt. If executing out of
* flash, these steps also changes the code flow from flash
* to external memory.
*/
serial_early_puts("Lower to 15");
r0 = r7;
r1 = r6;
p0.l = LO(EVT15);
p0.h = HI(EVT15);
p1.l = .Lenable_nested;
p1.h = .Lenable_nested;
[p0] = p1;
r7 = EVT_IVG15 (z);
sti r7;
raise 15;
p4.l = .LWAIT_HERE;
p4.h = .LWAIT_HERE;
reti = p4;
rti;
/* Enable nested interrupts before continuing with cpu init */
.Lenable_nested:
cli r7;
[--sp] = reti;
jump.l _cpu_init_f;
.LWAIT_HERE:
jump .LWAIT_HERE;
ENDPROC(_start)
LENTRY(_get_pc)
r0 = rets;
#if ANOMALY_05000371
NOP;
NOP;
NOP;
#endif
rts;
ENDPROC(_get_pc)
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