/*
 * Nios2-specific parts of system setup
 *
 * Copyright (C) 2010 Tobias Klauser <tklauser@distanz.ch>
 * Copyright (C) 2004 Microtronix Datacom Ltd.
 * Copyright (C) 2001 Vic Phillips <vic@microtronix.com>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/console.h>
#include <linux/memblock.h>
#include <linux/initrd.h>
#include <linux/of_fdt.h>

#include <asm/mmu_context.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/cpuinfo.h>

unsigned long memory_start;
EXPORT_SYMBOL(memory_start);

unsigned long memory_end;
EXPORT_SYMBOL(memory_end);

static struct pt_regs fake_regs = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                                        0, 0, 0, 0, 0, 0,
                                        0};

/* Copy a short hook instruction sequence to the exception address */
static inline void copy_exception_handler(unsigned int addr)
{
        unsigned int start = (unsigned int) exception_handler_hook;
        volatile unsigned int tmp = 0;

        if (start == addr) {
                /* The CPU exception address already points to the handler. */
                return;
        }

        __asm__ __volatile__ (
                "ldw    %2,0(%0)\n"
                "stw    %2,0(%1)\n"
                "ldw    %2,4(%0)\n"
                "stw    %2,4(%1)\n"
                "ldw    %2,8(%0)\n"
                "stw    %2,8(%1)\n"
                "flushd 0(%1)\n"
                "flushd 4(%1)\n"
                "flushd 8(%1)\n"
                "flushi %1\n"
                "addi   %1,%1,4\n"
                "flushi %1\n"
                "addi   %1,%1,4\n"
                "flushi %1\n"
                "flushp\n"
                : /* no output registers */
                : "r" (start), "r" (addr), "r" (tmp)
                : "memory"
        );
}

/* Copy the fast TLB miss handler */
static inline void copy_fast_tlb_miss_handler(unsigned int addr)
{
        unsigned int start = (unsigned int) fast_handler;
        unsigned int end = (unsigned int) fast_handler_end;
        volatile unsigned int tmp = 0;

        __asm__ __volatile__ (
                "1:\n"
                "       ldw     %3,0(%0)\n"
                "       stw     %3,0(%1)\n"
                "       flushd  0(%1)\n"
                "       flushi  %1\n"
                "       flushp\n"
                "       addi    %0,%0,4\n"
                "       addi    %1,%1,4\n"
                "       bne     %0,%2,1b\n"
                : /* no output registers */
                : "r" (start), "r" (addr), "r" (end), "r" (tmp)
                : "memory"
        );
}

/*
 * save args passed from u-boot, called from head.S
 *
 * @r4: NIOS magic
 * @r5: initrd start
 * @r6: initrd end or fdt
 * @r7: kernel command line
 */
asmlinkage void __init nios2_boot_init(unsigned r4, unsigned r5, unsigned r6,
                                       unsigned r7)
{
        unsigned dtb_passed = 0;
        char cmdline_passed[COMMAND_LINE_SIZE] __maybe_unused = { 0, };

#if defined(CONFIG_NIOS2_PASS_CMDLINE)
        if (r4 == 0x534f494e) { /* r4 is magic NIOS */
#if defined(CONFIG_BLK_DEV_INITRD)
                if (r5) { /* initramfs */
                        initrd_start = r5;
                        initrd_end = r6;
                }
#endif /* CONFIG_BLK_DEV_INITRD */
                dtb_passed = r6;

                if (r7)
                        strscpy(cmdline_passed, (char *)r7, COMMAND_LINE_SIZE);
        }
#endif

        early_init_devtree((void *)dtb_passed);

#ifndef CONFIG_CMDLINE_FORCE
        if (cmdline_passed[0])
                strscpy(boot_command_line, cmdline_passed, COMMAND_LINE_SIZE);
#ifdef CONFIG_NIOS2_CMDLINE_IGNORE_DTB
        else
                strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
#endif
#endif

        parse_early_param();
}

static void __init find_limits(unsigned long *min, unsigned long *max_low,
                               unsigned long *max_high)
{
        *max_low = PFN_DOWN(memblock_get_current_limit());
        *min = PFN_UP(memblock_start_of_DRAM());
        *max_high = PFN_DOWN(memblock_end_of_DRAM());
}

static void __init adjust_lowmem_bounds(void)
{
        phys_addr_t block_start, block_end;
        u64 i;
        phys_addr_t memblock_limit = 0;

        for_each_mem_range(i, &block_start, &block_end) {
                if (block_end > memblock_limit)
                        memblock_limit = block_end;
        }

        memblock_set_current_limit(memblock_limit);
}

void __init setup_arch(char **cmdline_p)
{
        console_verbose();

        memory_start = memblock_start_of_DRAM();
        memory_end = memblock_end_of_DRAM();

        pr_debug("%s: start=%lx, end=%lx\n", __func__, memory_start, memory_end);

        setup_initial_init_mm(_stext, _etext, _edata, _end);
        init_task.thread.kregs = &fake_regs;

        /* Keep a copy of command line */
        *cmdline_p = boot_command_line;

        adjust_lowmem_bounds();
        find_limits(&min_low_pfn, &max_low_pfn, &max_pfn);

        memblock_reserve(__pa_symbol(_stext), _end - _stext);
#ifdef CONFIG_BLK_DEV_INITRD
        if (initrd_start) {
                memblock_reserve(virt_to_phys((void *)initrd_start),
                                initrd_end - initrd_start);
        }
#endif /* CONFIG_BLK_DEV_INITRD */

        early_init_fdt_reserve_self();
        early_init_fdt_scan_reserved_mem();

        unflatten_and_copy_device_tree();

        setup_cpuinfo();

        copy_exception_handler(cpuinfo.exception_addr);

        mmu_init();

        copy_fast_tlb_miss_handler(cpuinfo.fast_tlb_miss_exc_addr);

        /*
         * Initialize MMU context handling here because data from cpuinfo is
         * needed for this.
         */
        mmu_context_init();

        /*
         * get kmalloc into gear
         */
        paging_init();
}