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/*
 * Copyright (C) 2005 Martin Decky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <arch/mm/page.h>
#include <genarch/mm/page_pt.h>
#include <arch/mm/frame.h>
#include <arch/asm.h>
#include <mm/frame.h>
#include <mm/page.h>
#include <mm/as.h>
#include <arch.h>
#include <arch/types.h>
#include <arch/exception.h>
#include <config.h>
#include <print.h>
#include <symtab.h>

static phte_t *phte;


/** Try to find PTE for faulting address
 *
 * Try to find PTE for faulting address.
 * The AS->lock must be held on entry to this function.
 *
 * @param badvaddr Faulting virtual address.
 * @param istate Pointer to interrupted state.
 * @param pfrc Pointer to variable where as_page_fault() return code will be stored.
 * @return         PTE on success, NULL otherwise.
 *
 */
static pte_t *find_mapping_and_check(__address badvaddr, istate_t *istate, int *pfcr)
{
    /*
     * Check if the mapping exists in page tables.
     */ 
    pte_t *pte = page_mapping_find(AS, badvaddr);
    if ((pte) && (pte->p)) {
        /*
         * Mapping found in page tables.
         * Immediately succeed.
         */
        return pte;
    } else {
        int rc;
    
        /*
         * Mapping not found in page tables.
         * Resort to higher-level page fault handler.
         */
        page_table_unlock(AS, true);
        switch (rc = as_page_fault(badvaddr, istate)) {
            case AS_PF_OK:
                /*
                 * The higher-level page fault handler succeeded,
                 * The mapping ought to be in place.
                 */
                page_table_lock(AS, true);
                pte = page_mapping_find(AS, badvaddr);
                ASSERT((pte) && (pte->p));
                return pte;
            case AS_PF_DEFER:
                page_table_lock(AS, true);
                *pfcr = rc;
                return NULL;
            case AS_PF_FAULT:
                page_table_lock(AS, true);
                printf("Page fault.\n");
                *pfcr = rc;
                return NULL;
            default:
                panic("unexpected rc (%d)\n", rc);
        }   
    }
}


static void pht_refill_fail(__address badvaddr, istate_t *istate)
{
    char *symbol = "";
    char *sym2 = "";

    char *s = get_symtab_entry(istate->pc);
    if (s)
        symbol = s;
    s = get_symtab_entry(istate->lr);
    if (s)
        sym2 = s;
    panic("%p: PHT Refill Exception at %p (%s<-%s)\n", badvaddr, istate->pc, symbol, sym2);
}

static void pht_insert(const __address vaddr, const pfn_t pfn)
{
    __u32 page = (vaddr >> 12) & 0xffff;
    __u32 api = (vaddr >> 22) & 0x3f;
    __u32 vsid;
    
    asm volatile (
        "mfsrin %0, %1\n"
        : "=r" (vsid)
        : "r" (vaddr)
    );
    
    /* Primary hash (xor) */
    __u32 hash = ((vsid ^ page) & 0x3ff) << 3;
    
    __u32 i;
    /* Find unused PTE in PTEG */
    for (i = 0; i < 8; i++) {
        if (!phte[hash + i].v)
            break;
    }
    
    // TODO: Check access/change bits, secondary hash
    
    if (i == 8) 
        i = page % 8;
    
    phte[hash + i].v = 1;
    phte[hash + i].vsid = vsid;
    phte[hash + i].h = 0;
    phte[hash + i].api = api;
    phte[hash + i].rpn = pfn;
    phte[hash + i].r = 0;
    phte[hash + i].c = 0;
    phte[hash + i].pp = 2; // FIXME
}


/** Process Instruction/Data Storage Interrupt
 *
 * @param data   True if Data Storage Interrupt.
 * @param istate Interrupted register context.
 *
 */
void pht_refill(bool data, istate_t *istate)
{
    asid_t asid;
    __address badvaddr;
    pte_t *pte;
    
    int pfcr;
    
    if (data) {
        asm volatile (
            "mfdar %0\n"
            : "=r" (badvaddr)
        );
    } else
        badvaddr = istate->pc;
        
    spinlock_lock(&AS->lock);
    asid = AS->asid;
    spinlock_unlock(&AS->lock);
    
    page_table_lock(AS, true);
    
    pte = find_mapping_and_check(badvaddr, istate, &pfcr);
    if (!pte) {
        switch (pfcr) {
        case AS_PF_FAULT:
            goto fail;
            break;
        case AS_PF_DEFER:
            /*
             * The page fault came during copy_from_uspace()
             * or copy_to_uspace().
             */
            page_table_unlock(AS, true);
            return;
        default:
            panic("Unexpected pfrc (%d)\n", pfcr);
            break;
        }
    }
    
    pte->a = 1; /* Record access to PTE */
    pht_insert(badvaddr, pte->pfn);
    
    page_table_unlock(AS, true);
    return;
    
fail:
    page_table_unlock(AS, true);
    pht_refill_fail(badvaddr, istate);
}


void pht_init(void)
{
    memsetb((__address) phte, 1 << PHT_BITS, 0);
    
    /* Insert global kernel mapping */
    
    __address cur;
    for (cur = 0; cur < last_frame; cur += FRAME_SIZE) {
        pte_t *pte = page_mapping_find(AS_KERNEL, PA2KA(cur));
        if ((pte) && (pte->p) && (pte->g))
            pht_insert(PA2KA(cur), pte->pfn);
    }
}


void page_arch_init(void)
{
    if (config.cpu_active == 1) {
        page_mapping_operations = &pt_mapping_operations;
        
        /*
         * PA2KA(identity) mapping for all frames until last_frame.
         */
        __address cur;
        int flags;
        
        for (cur = 0; cur < last_frame; cur += FRAME_SIZE) {
            flags = PAGE_CACHEABLE;
            if ((PA2KA(cur) >= config.base) && (PA2KA(cur) < config.base + config.kernel_size))
                flags |= PAGE_GLOBAL;
            page_mapping_insert(AS_KERNEL, PA2KA(cur), cur, flags);
        }
        
        /* Allocate page hash table */
        phte_t *physical_phte = (phte_t *) PFN2ADDR(frame_alloc(PHT_ORDER, FRAME_KA | FRAME_PANIC));
        phte = (phte_t *) PA2KA((__address) physical_phte);
        
        ASSERT((__address) physical_phte % (1 << PHT_BITS) == 0);
        pht_init();
        
        asm volatile (
            "mtsdr1 %0\n"
            :
            : "r" ((__address) physical_phte)
        );
        
        /* Invalidate block address translation registers,
           thus remove the temporary mapping */
//      invalidate_bat();
    }
}