/*
 * Early kernel startup code for Hexagon
 *
 * Copyright (c) 2010-2013, The Linux Foundation. All rights reserved.
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * 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 Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/linkage.h>
#include <linux/init.h>
#include <asm/asm-offsets.h>
#include <asm/mem-layout.h>
#include <asm/vm_mmu.h>
#include <asm/page.h>
#include <asm/hexagon_vm.h>

#define SEGTABLE_ENTRIES #0x0e0

        __INIT
ENTRY(stext)
        /*
         * VMM will already have set up true vector page, MMU, etc.
         * To set up initial kernel identity map, we have to pass
         * the VMM a pointer to some canonical page tables. In
         * this implementation, we're assuming that we've got
         * them precompiled. Generate value in R24, as we'll need
         * it again shortly.
         */
        r24.L = #LO(swapper_pg_dir)
        r24.H = #HI(swapper_pg_dir)

        /*
         * Symbol is kernel segment address, but we need
         * the logical/physical address.
         */
        r25 = pc;
        r2.h = #0xffc0;
        r2.l = #0x0000;
        r25 = and(r2,r25);      /*  R25 holds PHYS_OFFSET now  */
        r1.h = #HI(PAGE_OFFSET);
        r1.l = #LO(PAGE_OFFSET);
        r24 = sub(r24,r1);      /* swapper_pg_dir - PAGE_OFFSET */
        r24 = add(r24,r25);     /* + PHYS_OFFSET */

        r0 = r24;  /* aka __pa(swapper_pg_dir)  */

        /*
         * Initialize page dir to make the virtual and physical
         * addresses where the kernel was loaded be identical.
         * Done in 4MB chunks.
         */
#define PTE_BITS ( __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X      \
                  | __HEXAGON_C_WB_L2 << 6                      \
                  | __HVM_PDE_S_4MB)

        /*
         * Get number of VA=PA entries; only really needed for jump
         * to hyperspace; gets blown away immediately after
         */

        {
                r1.l = #LO(_end);
                r2.l = #LO(stext);
                r3 = #1;
        }
        {
                r1.h = #HI(_end);
                r2.h = #HI(stext);
                r3 = asl(r3, #22);
        }
        {
                r1 = sub(r1, r2);
                r3 = add(r3, #-1);
        }  /* r1 =  _end - stext  */
        r1 = add(r1, r3);  /*  + (4M-1) */
        r26 = lsr(r1, #22); /*  / 4M = # of entries */

        r1 = r25;
        r2.h = #0xffc0;
        r2.l = #0x0000;         /* round back down to 4MB boundary  */
        r1 = and(r1,r2);
        r2 = lsr(r1, #22)       /* 4MB page number              */
        r2 = asl(r2, #2)        /* times sizeof(PTE) (4bytes)   */
        r0 = add(r0,r2)         /* r0 = address of correct PTE  */
        r2 = #PTE_BITS
        r1 = add(r1,r2)         /* r1 = 4MB PTE for the first entry     */
        r2.h = #0x0040
        r2.l = #0x0000          /* 4MB increments */
        loop0(1f,r26);
1:
        memw(r0 ++ #4) = r1
        { r1 = add(r1, r2); } :endloop0

        /*  Also need to overwrite the initial 0xc0000000 entries  */
        /*  PAGE_OFFSET >> (4MB shift - 4 bytes per entry shift)  */
        R1.H = #HI(PAGE_OFFSET >> (22 - 2))
        R1.L = #LO(PAGE_OFFSET >> (22 - 2))

        r0 = add(r1, r24);      /* advance to 0xc0000000 entry */
        r1 = r25;
        r2.h = #0xffc0;
        r2.l = #0x0000;         /* round back down to 4MB boundary  */
        r1 = and(r1,r2);        /* for huge page */
        r2 = #PTE_BITS
        r1 = add(r1,r2);
        r2.h = #0x0040
        r2.l = #0x0000          /* 4MB increments */

        loop0(1f,SEGTABLE_ENTRIES);
1:
        memw(r0 ++ #4) = r1;
        { r1 = add(r1,r2); } :endloop0

        r0 = r24;

        /*
         * The subroutine wrapper around the virtual instruction touches
         * no memory, so we should be able to use it even here.
         * Note that in this version, R1 and R2 get "clobbered"; see
         * vm_ops.S
         */
        r1 = #VM_TRANS_TYPE_TABLE
        call    __vmnewmap;

        /*  Jump into virtual address range.  */

        r31.h = #hi(__head_s_vaddr_target)
        r31.l = #lo(__head_s_vaddr_target)
        jumpr r31

        /*  Insert trippy space effects.  */

__head_s_vaddr_target:
        /*
         * Tear down VA=PA translation now that we are running
         * in kernel virtual space.
         */
        r0 = #__HVM_PDE_S_INVALID

        r1.h = #0xffc0;
        r1.l = #0x0000;
        r2 = r25;               /* phys_offset */
        r2 = and(r1,r2);

        r1.l = #lo(swapper_pg_dir)
        r1.h = #hi(swapper_pg_dir)
        r2 = lsr(r2, #22)       /* 4MB page number              */
        r2 = asl(r2, #2)        /* times sizeof(PTE) (4bytes)   */
        r1 = add(r1,r2);
        loop0(1f,r26)

1:
        {
                memw(R1 ++ #4) = R0
        }:endloop0

        r0 = r24
        r1 = #VM_TRANS_TYPE_TABLE
        call __vmnewmap

        /*  Go ahead and install the trap0 return so angel calls work  */
        r0.h = #hi(_K_provisional_vec)
        r0.l = #lo(_K_provisional_vec)
        call __vmsetvec

        /*
         * OK, at this point we should start to be much more careful,
         * we're going to enter C code and start touching memory
         * in all sorts of places.
         * This means:
         *      SGP needs to be OK
         *      Need to lock shared resources
         *      A bunch of other things that will cause
         *      all kinds of painful bugs
         */

        /*
         * Stack pointer should be pointed at the init task's
         * thread stack, which should have been declared in arch/init_task.c.
         * So uhhhhh...
         * It's accessible via the init_thread_union, which is a union
         * of a thread_info struct and a stack; of course, the top
         * of the stack is not for you.  The end of the stack
         * is simply init_thread_union + THREAD_SIZE.
         */

        {r29.H = #HI(init_thread_union); r0.H = #HI(_THREAD_SIZE); }
        {r29.L = #LO(init_thread_union); r0.L = #LO(_THREAD_SIZE); }

        /*  initialize the register used to point to current_thread_info */
        /*  Fixme:  THREADINFO_REG can't be R2 because of that memset thing. */
        {r29 = add(r29,r0); THREADINFO_REG = r29; }

        /*  Hack:  zero bss; */
        { r0.L = #LO(__bss_start);  r1 = #0; r2.l = #LO(__bss_stop); }
        { r0.H = #HI(__bss_start);           r2.h = #HI(__bss_stop); }

        r2 = sub(r2,r0);
        call memset;

        /*  Set PHYS_OFFSET; should be in R25 */
#ifdef CONFIG_HEXAGON_PHYS_OFFSET
        r0.l = #LO(__phys_offset);
        r0.h = #HI(__phys_offset);
        memw(r0) = r25;
#endif

        /* Time to make the doughnuts.   */
        call start_kernel

        /*
         * Should not reach here.
         */
1:
        jump 1b

.p2align PAGE_SHIFT
ENTRY(external_cmdline_buffer)
        .fill _PAGE_SIZE,1,0

.data
.p2align PAGE_SHIFT
ENTRY(empty_zero_page)
        .fill _PAGE_SIZE,1,0