188 lines
4.0 KiB
C
188 lines
4.0 KiB
C
/*
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* cpu.c - A few helper functions for ARM
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*
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* Copyright (c) 2007 Sascha Hauer <s.hauer@pengutronix.de>, Pengutronix
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*
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* See file CREDITS for list of people who contributed to this
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* project.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/**
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* @file
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* @brief A few helper functions for ARM
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*/
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#include <common.h>
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#include <command.h>
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#include <asm/mmu.h>
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/**
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* Read special processor register
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* @return co-processor 15, register #1 (control register)
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*/
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static unsigned long read_p15_c1 (void)
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{
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unsigned long value;
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__asm__ __volatile__(
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"mrc p15, 0, %0, c1, c0, 0 @ read control reg\n"
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: "=r" (value)
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:
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: "memory");
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#ifdef MMU_DEBUG
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printf ("p15/c1 is = %08lx\n", value);
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#endif
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return value;
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}
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/**
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*
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* Write special processor register
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* @param[in] value to write
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* @return to co-processor 15, register #1 (control register)
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*/
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static void write_p15_c1 (unsigned long value)
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{
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#ifdef MMU_DEBUG
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printf ("write %08lx to p15/c1\n", value);
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#endif
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__asm__ __volatile__(
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"mcr p15, 0, %0, c1, c0, 0 @ write it back\n"
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:
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: "r" (value)
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: "memory");
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read_p15_c1 ();
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}
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/**
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* Wait for co prozessor (waste time)
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* Co processor seems to need some delay between accesses
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*/
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static void cp_delay (void)
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{
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volatile int i;
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for (i = 0; i < 100; i++) /* FIXME does it work as expected?? */
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;
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}
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/** mmu off/on */
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#define C1_MMU (1<<0)
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/** alignment faults off/on */
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#define C1_ALIGN (1<<1)
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/** dcache off/on */
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#define C1_DC (1<<2)
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/** big endian off/on */
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#define C1_BIG_ENDIAN (1<<7)
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/** system protection */
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#define C1_SYS_PROT (1<<8)
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/** ROM protection */
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#define C1_ROM_PROT (1<<9)
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/** icache off/on */
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#define C1_IC (1<<12)
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/** location of vectors: low/high addresses */
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#define C1_HIGH_VECTORS (1<<13)
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/**
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* Enable processor's instruction cache
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*/
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void icache_enable (void)
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{
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ulong reg;
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reg = read_p15_c1 (); /* get control reg. */
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cp_delay ();
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write_p15_c1 (reg | C1_IC);
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}
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/**
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* Disable processor's instruction cache
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*/
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void icache_disable (void)
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{
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ulong reg;
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reg = read_p15_c1 ();
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cp_delay ();
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write_p15_c1 (reg & ~C1_IC);
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}
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/**
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* Detect processor's current instruction cache status
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* @return 0=disabled, 1=enabled
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*/
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int icache_status (void)
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{
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return (read_p15_c1 () & C1_IC) != 0;
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}
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/**
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* Prepare a "clean" CPU for Linux to run
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* @return 0 (always)
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*
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* This function is called by the generic barebox part just before we call
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* Linux. It prepares the processor for Linux.
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*/
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int cleanup_before_linux (void)
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{
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int i;
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shutdown_barebox();
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#ifdef CONFIG_MMU
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mmu_disable();
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#endif
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/* flush I/D-cache */
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i = 0;
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asm ("mcr p15, 0, %0, c7, c7, 0": :"r" (i));
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return 0;
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}
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/**
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* @page arm_boot_preparation Linux Preparation on ARM
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*
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* For ARM we never enable data cache so we do not need to disable it again.
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* Linux can be called with instruction cache enabled. As this is the
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* default setting we are running in barebox, there's no special preparation
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* required.
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*/
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static int do_icache(cmd_tbl_t *cmdtp, int argc, char *argv[])
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{
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if (argc == 1) {
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printf("icache is %sabled\n", icache_status() ? "en" : "dis");
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return 0;
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}
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if (simple_strtoul(argv[1], NULL, 0) > 0)
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icache_enable();
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else
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icache_disable();
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return 0;
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}
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static const __maybe_unused char cmd_icache_help[] =
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"Usage: icache [0|1]\n";
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BAREBOX_CMD_START(icache)
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.cmd = do_icache,
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.usage = "show/change icache status",
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BAREBOX_CMD_HELP(cmd_icache_help)
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BAREBOX_CMD_END
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