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Diffstat (limited to 'arch/blackfin/cpu/start.S')
| -rw-r--r-- | arch/blackfin/cpu/start.S | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/arch/blackfin/cpu/start.S b/arch/blackfin/cpu/start.S new file mode 100644 index 0000000..7a3abba --- /dev/null +++ b/arch/blackfin/cpu/start.S @@ -0,0 +1,238 @@ +/* + * 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; + +#if CONFIG_MEM_SIZE + /* 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; +#else + r6 = 1 (x); /* fake loaded_from_ldr = 1 */ +#endif + 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 + +#if CONFIG_MEM_SIZE + /* 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; +#endif + + /* 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) |