/*
 * PowerPC64 Segment Translation Support.
 *
 * Dave Engebretsen and Mike Corrigan {engebret|mikejc}@us.ibm.com
 *    Copyright (c) 2001 Dave Engebretsen
 *
 * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
 *
 *      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.
 */

#include <linux/lmb.h>

#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/paca.h>
#include <asm/cputable.h>
#include <asm/prom.h>
#include <asm/abs_addr.h>
#include <asm/firmware.h>
#include <asm/iseries/hv_call.h>

struct stab_entry {
        unsigned long esid_data;
        unsigned long vsid_data;
};

#define NR_STAB_CACHE_ENTRIES 8
static DEFINE_PER_CPU(long, stab_cache_ptr);
static DEFINE_PER_CPU(long [NR_STAB_CACHE_ENTRIES], stab_cache);

/*
 * Create a segment table entry for the given esid/vsid pair.
 */
static int make_ste(unsigned long stab, unsigned long esid, unsigned long vsid)
{
        unsigned long esid_data, vsid_data;
        unsigned long entry, group, old_esid, castout_entry, i;
        unsigned int global_entry;
        struct stab_entry *ste, *castout_ste;
        unsigned long kernel_segment = (esid << SID_SHIFT) >= PAGE_OFFSET;

        vsid_data = vsid << STE_VSID_SHIFT;
        esid_data = esid << SID_SHIFT | STE_ESID_KP | STE_ESID_V;
        if (! kernel_segment)
                esid_data |= STE_ESID_KS;

        /* Search the primary group first. */
        global_entry = (esid & 0x1f) << 3;
        ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));

        /* Find an empty entry, if one exists. */
        for (group = 0; group < 2; group++) {
                for (entry = 0; entry < 8; entry++, ste++) {
                        if (!(ste->esid_data & STE_ESID_V)) {
                                ste->vsid_data = vsid_data;
                                eieio();
                                ste->esid_data = esid_data;
                                return (global_entry | entry);
                        }
                }
                /* Now search the secondary group. */
                global_entry = ((~esid) & 0x1f) << 3;
                ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
        }

        /*
         * Could not find empty entry, pick one with a round robin selection.
         * Search all entries in the two groups.
         */
        castout_entry = get_paca()->stab_rr;
        for (i = 0; i < 16; i++) {
                if (castout_entry < 8) {
                        global_entry = (esid & 0x1f) << 3;
                        ste = (struct stab_entry *)(stab | ((esid & 0x1f) << 7));
                        castout_ste = ste + castout_entry;
                } else {
                        global_entry = ((~esid) & 0x1f) << 3;
                        ste = (struct stab_entry *)(stab | (((~esid) & 0x1f) << 7));
                        castout_ste = ste + (castout_entry - 8);
                }

                /* Dont cast out the first kernel segment */
                if ((castout_ste->esid_data & ESID_MASK) != PAGE_OFFSET)
                        break;

                castout_entry = (castout_entry + 1) & 0xf;
        }

        get_paca()->stab_rr = (castout_entry + 1) & 0xf;

        /* Modify the old entry to the new value. */

        /* Force previous translations to complete. DRENG */
        asm volatile("isync" : : : "memory");

        old_esid = castout_ste->esid_data >> SID_SHIFT;
        castout_ste->esid_data = 0;             /* Invalidate old entry */

        asm volatile("sync" : : : "memory");    /* Order update */

        castout_ste->vsid_data = vsid_data;
        eieio();                                /* Order update */
        castout_ste->esid_data = esid_data;

        asm volatile("slbie  %0" : : "r" (old_esid << SID_SHIFT));
        /* Ensure completion of slbie */
        asm volatile("sync" : : : "memory");

        return (global_entry | (castout_entry & 0x7));
}

/*
 * Allocate a segment table entry for the given ea and mm
 */
static int __ste_allocate(unsigned long ea, struct mm_struct *mm)
{
        unsigned long vsid;
        unsigned char stab_entry;
        unsigned long offset;

        /* Kernel or user address? */
        if (is_kernel_addr(ea)) {
                vsid = get_kernel_vsid(ea, MMU_SEGSIZE_256M);
        } else {
                if ((ea >= TASK_SIZE_USER64) || (! mm))
                        return 1;

                vsid = get_vsid(mm->context.id, ea, MMU_SEGSIZE_256M);
        }

        stab_entry = make_ste(get_paca()->stab_addr, GET_ESID(ea), vsid);

        if (!is_kernel_addr(ea)) {
                offset = __get_cpu_var(stab_cache_ptr);
                if (offset < NR_STAB_CACHE_ENTRIES)
                        __get_cpu_var(stab_cache[offset++]) = stab_entry;
                else
                        offset = NR_STAB_CACHE_ENTRIES+1;
                __get_cpu_var(stab_cache_ptr) = offset;

                /* Order update */
                asm volatile("sync":::"memory");
        }

        return 0;
}

int ste_allocate(unsigned long ea)
{
        return __ste_allocate(ea, current->mm);
}

/*
 * Do the segment table work for a context switch: flush all user
 * entries from the table, then preload some probably useful entries
 * for the new task
 */
void switch_stab(struct task_struct *tsk, struct mm_struct *mm)
{
        struct stab_entry *stab = (struct stab_entry *) get_paca()->stab_addr;
        struct stab_entry *ste;
        unsigned long offset;
        unsigned long pc = KSTK_EIP(tsk);
        unsigned long stack = KSTK_ESP(tsk);
        unsigned long unmapped_base;

        /* Force previous translations to complete. DRENG */
        asm volatile("isync" : : : "memory");

        /*
         * We need interrupts hard-disabled here, not just soft-disabled,
         * so that a PMU interrupt can't occur, which might try to access
         * user memory (to get a stack trace) and possible cause an STAB miss
         * which would update the stab_cache/stab_cache_ptr per-cpu variables.
         */
        hard_irq_disable();

        offset = __get_cpu_var(stab_cache_ptr);
        if (offset <= NR_STAB_CACHE_ENTRIES) {
                int i;

                for (i = 0; i < offset; i++) {
                        ste = stab + __get_cpu_var(stab_cache[i]);
                        ste->esid_data = 0; /* invalidate entry */
                }
        } else {
                unsigned long entry;

                /* Invalidate all entries. */
                ste = stab;

                /* Never flush the first entry. */
                ste += 1;
                for (entry = 1;
                     entry < (HW_PAGE_SIZE / sizeof(struct stab_entry));
                     entry++, ste++) {
                        unsigned long ea;
                        ea = ste->esid_data & ESID_MASK;
                        if (!is_kernel_addr(ea)) {
                                ste->esid_data = 0;
                        }
                }
        }

        asm volatile("sync; slbia; sync":::"memory");

        __get_cpu_var(stab_cache_ptr) = 0;

        /* Now preload some entries for the new task */
        if (test_tsk_thread_flag(tsk, TIF_32BIT))
                unmapped_base = TASK_UNMAPPED_BASE_USER32;
        else
                unmapped_base = TASK_UNMAPPED_BASE_USER64;

        __ste_allocate(pc, mm);

        if (GET_ESID(pc) == GET_ESID(stack))
                return;

        __ste_allocate(stack, mm);

        if ((GET_ESID(pc) == GET_ESID(unmapped_base))
            || (GET_ESID(stack) == GET_ESID(unmapped_base)))
                return;

        __ste_allocate(unmapped_base, mm);

        /* Order update */
        asm volatile("sync" : : : "memory");
}

/*
 * Allocate segment tables for secondary CPUs.  These must all go in
 * the first (bolted) segment, so that do_stab_bolted won't get a
 * recursive segment miss on the segment table itself.
 */
void __init stabs_alloc(void)
{
        int cpu;

        if (cpu_has_feature(CPU_FTR_SLB))
                return;

        for_each_possible_cpu(cpu) {
                unsigned long newstab;

                if (cpu == 0)
                        continue; /* stab for CPU 0 is statically allocated */

                newstab = lmb_alloc_base(HW_PAGE_SIZE, HW_PAGE_SIZE,
                                         1<<SID_SHIFT);
                newstab = (unsigned long)__va(newstab);

                memset((void *)newstab, 0, HW_PAGE_SIZE);

                paca[cpu].stab_addr = newstab;
                paca[cpu].stab_real = virt_to_abs(newstab);
                printk(KERN_INFO "Segment table for CPU %d at 0x%llx "
                       "virtual, 0x%llx absolute\n",
                       cpu, paca[cpu].stab_addr, paca[cpu].stab_real);
        }
}

/*
 * Build an entry for the base kernel segment and put it into
 * the segment table or SLB.  All other segment table or SLB
 * entries are faulted in.
 */
void stab_initialize(unsigned long stab)
{
        unsigned long vsid = get_kernel_vsid(PAGE_OFFSET, MMU_SEGSIZE_256M);
        unsigned long stabreal;

        asm volatile("isync; slbia; isync":::"memory");
        make_ste(stab, GET_ESID(PAGE_OFFSET), vsid);

        /* Order update */
        asm volatile("sync":::"memory");

        /* Set ASR */
        stabreal = get_paca()->stab_real | 0x1ul;

#ifdef CONFIG_PPC_ISERIES
        if (firmware_has_feature(FW_FEATURE_ISERIES)) {
                HvCall1(HvCallBaseSetASR, stabreal);
                return;
        }
#endif /* CONFIG_PPC_ISERIES */

        mtspr(SPRN_ASR, stabreal);
}