ARC: No need to flush the TLB in early boot

[~andy/linux] / arch / arc / mm / tlb.c

/*
 * TLB Management (flush/create/diagnostics) for ARC700
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * vineetg: Aug 2011
 *  -Reintroduce duplicate PD fixup - some customer chips still have the issue
 *
 * vineetg: May 2011
 *  -No need to flush_cache_page( ) for each call to update_mmu_cache()
 *   some of the LMBench tests improved amazingly
 *      = page-fault thrice as fast (75 usec to 28 usec)
 *      = mmap twice as fast (9.6 msec to 4.6 msec),
 *      = fork (5.3 msec to 3.7 msec)
 *
 * vineetg: April 2011 :
 *  -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore,
 *      helps avoid a shift when preparing PD0 from PTE
 *
 * vineetg: April 2011 : Preparing for MMU V3
 *  -MMU v2/v3 BCRs decoded differently
 *  -Remove TLB_SIZE hardcoding as it's variable now: 256 or 512
 *  -tlb_entry_erase( ) can be void
 *  -local_flush_tlb_range( ):
 *      = need not "ceil" @end
 *      = walks MMU only if range spans < 32 entries, as opposed to 256
 *
 * Vineetg: Sept 10th 2008
 *  -Changes related to MMU v2 (Rel 4.8)
 *
 * Vineetg: Aug 29th 2008
 *  -In TLB Flush operations (Metal Fix MMU) there is a explict command to
 *    flush Micro-TLBS. If TLB Index Reg is invalid prior to TLBIVUTLB cmd,
 *    it fails. Thus need to load it with ANY valid value before invoking
 *    TLBIVUTLB cmd
 *
 * Vineetg: Aug 21th 2008:
 *  -Reduced the duration of IRQ lockouts in TLB Flush routines
 *  -Multiple copies of TLB erase code seperated into a "single" function
 *  -In TLB Flush routines, interrupt disabling moved UP to retrieve ASID
 *       in interrupt-safe region.
 *
 * Vineetg: April 23rd Bug #93131
 *    Problem: tlb_flush_kernel_range() doesnt do anything if the range to
 *              flush is more than the size of TLB itself.
 *
 * Rahul Trivedi : Codito Technologies 2004
 */

#include <linux/module.h>
#include <linux/bug.h>
#include <asm/arcregs.h>
#include <asm/setup.h>
#include <asm/mmu_context.h>
#include <asm/mmu.h>

/*                      Need for ARC MMU v2
 *
 * ARC700 MMU-v1 had a Joint-TLB for Code and Data and is 2 way set-assoc.
 * For a memcpy operation with 3 players (src/dst/code) such that all 3 pages
 * map into same set, there would be contention for the 2 ways causing severe
 * Thrashing.
 *
 * Although J-TLB is 2 way set assoc, ARC700 caches J-TLB into uTLBS which has
 * much higher associativity. u-D-TLB is 8 ways, u-I-TLB is 4 ways.
 * Given this, the thrasing problem should never happen because once the 3
 * J-TLB entries are created (even though 3rd will knock out one of the prev
 * two), the u-D-TLB and u-I-TLB will have what is required to accomplish memcpy
 *
 * Yet we still see the Thrashing because a J-TLB Write cause flush of u-TLBs.
 * This is a simple design for keeping them in sync. So what do we do?
 * The solution which James came up was pretty neat. It utilised the assoc
 * of uTLBs by not invalidating always but only when absolutely necessary.
 *
 * - Existing TLB commands work as before
 * - New command (TLBWriteNI) for TLB write without clearing uTLBs
 * - New command (TLBIVUTLB) to invalidate uTLBs.
 *
 * The uTLBs need only be invalidated when pages are being removed from the
 * OS page table. If a 'victim' TLB entry is being overwritten in the main TLB
 * as a result of a miss, the removed entry is still allowed to exist in the
 * uTLBs as it is still valid and present in the OS page table. This allows the
 * full associativity of the uTLBs to hide the limited associativity of the main
 * TLB.
 *
 * During a miss handler, the new "TLBWriteNI" command is used to load
 * entries without clearing the uTLBs.
 *
 * When the OS page table is updated, TLB entries that may be associated with a
 * removed page are removed (flushed) from the TLB using TLBWrite. In this
 * circumstance, the uTLBs must also be cleared. This is done by using the
 * existing TLBWrite command. An explicit IVUTLB is also required for those
 * corner cases when TLBWrite was not executed at all because the corresp
 * J-TLB entry got evicted/replaced.
 */


/* A copy of the ASID from the PID reg is kept in asid_cache */
int asid_cache = FIRST_ASID;

/* ASID to mm struct mapping. We have one extra entry corresponding to
 * NO_ASID to save us a compare when clearing the mm entry for old asid
 * see get_new_mmu_context (asm-arc/mmu_context.h)
 */
struct mm_struct *asid_mm_map[NUM_ASID + 1];

/*
 * Utility Routine to erase a J-TLB entry
 * Caller needs to setup Index Reg (manually or via getIndex)
 */
static inline void __tlb_entry_erase(void)
{
        write_aux_reg(ARC_REG_TLBPD1, 0);
        write_aux_reg(ARC_REG_TLBPD0, 0);
        write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite);
}

static inline unsigned int tlb_entry_lkup(unsigned long vaddr_n_asid)
{
        unsigned int idx;

        write_aux_reg(ARC_REG_TLBPD0, vaddr_n_asid);

        write_aux_reg(ARC_REG_TLBCOMMAND, TLBProbe);
        idx = read_aux_reg(ARC_REG_TLBINDEX);

        return idx;
}

static void tlb_entry_erase(unsigned int vaddr_n_asid)
{
        unsigned int idx;

        /* Locate the TLB entry for this vaddr + ASID */
        idx = tlb_entry_lkup(vaddr_n_asid);

        /* No error means entry found, zero it out */
        if (likely(!(idx & TLB_LKUP_ERR))) {
                __tlb_entry_erase();
        } else {
                /* Duplicate entry error */
                WARN(idx == TLB_DUP_ERR, "Probe returned Dup PD for %x\n",
                                           vaddr_n_asid);
        }
}

/****************************************************************************
 * ARC700 MMU caches recently used J-TLB entries (RAM) as uTLBs (FLOPs)
 *
 * New IVUTLB cmd in MMU v2 explictly invalidates the uTLB
 *
 * utlb_invalidate ( )
 *  -For v2 MMU calls Flush uTLB Cmd
 *  -For v1 MMU does nothing (except for Metal Fix v1 MMU)
 *      This is because in v1 TLBWrite itself invalidate uTLBs
 ***************************************************************************/

static void utlb_invalidate(void)
{
#if (CONFIG_ARC_MMU_VER >= 2)

#if (CONFIG_ARC_MMU_VER == 2)
        /* MMU v2 introduced the uTLB Flush command.
         * There was however an obscure hardware bug, where uTLB flush would
         * fail when a prior probe for J-TLB (both totally unrelated) would
         * return lkup err - because the entry didnt exist in MMU.
         * The Workround was to set Index reg with some valid value, prior to
         * flush. This was fixed in MMU v3 hence not needed any more
         */
        unsigned int idx;

        /* make sure INDEX Reg is valid */
        idx = read_aux_reg(ARC_REG_TLBINDEX);

        /* If not write some dummy val */
        if (unlikely(idx & TLB_LKUP_ERR))
                write_aux_reg(ARC_REG_TLBINDEX, 0xa);
#endif

        write_aux_reg(ARC_REG_TLBCOMMAND, TLBIVUTLB);
#endif

}

static void tlb_entry_insert(unsigned int pd0, unsigned int pd1)
{
        unsigned int idx;

        /*
         * First verify if entry for this vaddr+ASID already exists
         * This also sets up PD0 (vaddr, ASID..) for final commit
         */
        idx = tlb_entry_lkup(pd0);

        /*
         * If Not already present get a free slot from MMU.
         * Otherwise, Probe would have located the entry and set INDEX Reg
         * with existing location. This will cause Write CMD to over-write
         * existing entry with new PD0 and PD1
         */
        if (likely(idx & TLB_LKUP_ERR))
                write_aux_reg(ARC_REG_TLBCOMMAND, TLBGetIndex);

        /* setup the other half of TLB entry (pfn, rwx..) */
        write_aux_reg(ARC_REG_TLBPD1, pd1);

        /*
         * Commit the Entry to MMU
         * It doesnt sound safe to use the TLBWriteNI cmd here
         * which doesn't flush uTLBs. I'd rather be safe than sorry.
         */
        write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite);
}

/*
 * Un-conditionally (without lookup) erase the entire MMU contents
 */

noinline void local_flush_tlb_all(void)
{
        unsigned long flags;
        unsigned int entry;
        struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;

        local_irq_save(flags);

        /* Load PD0 and PD1 with template for a Blank Entry */
        write_aux_reg(ARC_REG_TLBPD1, 0);
        write_aux_reg(ARC_REG_TLBPD0, 0);

        for (entry = 0; entry < mmu->num_tlb; entry++) {
                /* write this entry to the TLB */
                write_aux_reg(ARC_REG_TLBINDEX, entry);
                write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite);
        }

        utlb_invalidate();

        local_irq_restore(flags);
}

/*
 * Flush the entrie MM for userland. The fastest way is to move to Next ASID
 */
noinline void local_flush_tlb_mm(struct mm_struct *mm)
{
        /*
         * Small optimisation courtesy IA64
         * flush_mm called during fork,exit,munmap etc, multiple times as well.
         * Only for fork( ) do we need to move parent to a new MMU ctxt,
         * all other cases are NOPs, hence this check.
         */
        if (atomic_read(&mm->mm_users) == 0)
                return;

        /*
         * Workaround for Android weirdism:
         * A binder VMA could end up in a task such that vma->mm != tsk->mm
         * old code would cause h/w - s/w ASID to get out of sync
         */
        if (current->mm != mm)
                destroy_context(mm);
        else
                get_new_mmu_context(mm);
}

/*
 * Flush a Range of TLB entries for userland.
 * @start is inclusive, while @end is exclusive
 * Difference between this and Kernel Range Flush is
 *  -Here the fastest way (if range is too large) is to move to next ASID
 *      without doing any explicit Shootdown
 *  -In case of kernel Flush, entry has to be shot down explictly
 */
void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
                           unsigned long end)
{
        unsigned long flags;
        unsigned int asid;

        /* If range @start to @end is more than 32 TLB entries deep,
         * its better to move to a new ASID rather than searching for
         * individual entries and then shooting them down
         *
         * The calc above is rough, doesn't account for unaligned parts,
         * since this is heuristics based anyways
         */
        if (unlikely((end - start) >= PAGE_SIZE * 32)) {
                local_flush_tlb_mm(vma->vm_mm);
                return;
        }

        /*
         * @start moved to page start: this alone suffices for checking
         * loop end condition below, w/o need for aligning @end to end
         * e.g. 2000 to 4001 will anyhow loop twice
         */
        start &= PAGE_MASK;

        local_irq_save(flags);
        asid = vma->vm_mm->context.asid;

        if (asid != NO_ASID) {
                while (start < end) {
                        tlb_entry_erase(start | (asid & 0xff));
                        start += PAGE_SIZE;
                }
        }

        utlb_invalidate();

        local_irq_restore(flags);
}

/* Flush the kernel TLB entries - vmalloc/modules (Global from MMU perspective)
 *  @start, @end interpreted as kvaddr
 * Interestingly, shared TLB entries can also be flushed using just
 * @start,@end alone (interpreted as user vaddr), although technically SASID
 * is also needed. However our smart TLbProbe lookup takes care of that.
 */
void local_flush_tlb_kernel_range(unsigned long start, unsigned long end)
{
        unsigned long flags;

        /* exactly same as above, except for TLB entry not taking ASID */

        if (unlikely((end - start) >= PAGE_SIZE * 32)) {
                local_flush_tlb_all();
                return;
        }

        start &= PAGE_MASK;

        local_irq_save(flags);
        while (start < end) {
                tlb_entry_erase(start);
                start += PAGE_SIZE;
        }

        utlb_invalidate();

        local_irq_restore(flags);
}

/*
 * Delete TLB entry in MMU for a given page (??? address)
 * NOTE One TLB entry contains translation for single PAGE
 */

void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
        unsigned long flags;

        /* Note that it is critical that interrupts are DISABLED between
         * checking the ASID and using it flush the TLB entry
         */
        local_irq_save(flags);

        if (vma->vm_mm->context.asid != NO_ASID) {
                tlb_entry_erase((page & PAGE_MASK) |
                                (vma->vm_mm->context.asid & 0xff));
                utlb_invalidate();
        }

        local_irq_restore(flags);
}

/*
 * Routine to create a TLB entry
 */
void create_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep)
{
        unsigned long flags;
        unsigned int asid_or_sasid, rwx;
        unsigned long pd0, pd1;

        /*
         * create_tlb() assumes that current->mm == vma->mm, since
         * -it ASID for TLB entry is fetched from MMU ASID reg (valid for curr)
         * -completes the lazy write to SASID reg (again valid for curr tsk)
         *
         * Removing the assumption involves
         * -Using vma->mm->context{ASID,SASID}, as opposed to MMU reg.
         * -Fix the TLB paranoid debug code to not trigger false negatives.
         * -More importantly it makes this handler inconsistent with fast-path
         *  TLB Refill handler which always deals with "current"
         *
         * Lets see the use cases when current->mm != vma->mm and we land here
         *  1. execve->copy_strings()->__get_user_pages->handle_mm_fault
         *     Here VM wants to pre-install a TLB entry for user stack while
         *     current->mm still points to pre-execve mm (hence the condition).
         *     However the stack vaddr is soon relocated (randomization) and
         *     move_page_tables() tries to undo that TLB entry.
         *     Thus not creating TLB entry is not any worse.
         *
         *  2. ptrace(POKETEXT) causes a CoW - debugger(current) inserting a
         *     breakpoint in debugged task. Not creating a TLB now is not
         *     performance critical.
         *
         * Both the cases above are not good enough for code churn.
         */
        if (current->active_mm != vma->vm_mm)
                return;

        local_irq_save(flags);

        tlb_paranoid_check(vma->vm_mm->context.asid, address);

        address &= PAGE_MASK;

        /* update this PTE credentials */
        pte_val(*ptep) |= (_PAGE_PRESENT | _PAGE_ACCESSED);

        /* Create HW TLB(PD0,PD1) from PTE  */

        /* ASID for this task */
        asid_or_sasid = read_aux_reg(ARC_REG_PID) & 0xff;

        pd0 = address | asid_or_sasid | (pte_val(*ptep) & PTE_BITS_IN_PD0);

        /*
         * ARC MMU provides fully orthogonal access bits for K/U mode,
         * however Linux only saves 1 set to save PTE real-estate
         * Here we convert 3 PTE bits into 6 MMU bits:
         * -Kernel only entries have Kr Kw Kx 0 0 0
         * -User entries have mirrored K and U bits
         */
        rwx = pte_val(*ptep) & PTE_BITS_RWX;

        if (pte_val(*ptep) & _PAGE_GLOBAL)
                rwx <<= 3;              /* r w x => Kr Kw Kx 0 0 0 */
        else
                rwx |= (rwx << 3);      /* r w x => Kr Kw Kx Ur Uw Ux */

        pd1 = rwx | (pte_val(*ptep) & PTE_BITS_NON_RWX_IN_PD1);

        tlb_entry_insert(pd0, pd1);

        local_irq_restore(flags);
}

/*
 * Called at the end of pagefault, for a userspace mapped page
 *  -pre-install the corresponding TLB entry into MMU
 *  -Finalize the delayed D-cache flush of kernel mapping of page due to
 *      flush_dcache_page(), copy_user_page()
 *
 * Note that flush (when done) involves both WBACK - so physical page is
 * in sync as well as INV - so any non-congruent aliases don't remain
 */
void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr_unaligned,
                      pte_t *ptep)
{
        unsigned long vaddr = vaddr_unaligned & PAGE_MASK;
        unsigned long paddr = pte_val(*ptep) & PAGE_MASK;
        struct page *page = pfn_to_page(pte_pfn(*ptep));

        create_tlb(vma, vaddr, ptep);

        if (page == ZERO_PAGE(0)) {
                return;
        }

        /*
         * Exec page : Independent of aliasing/page-color considerations,
         *             since icache doesn't snoop dcache on ARC, any dirty
         *             K-mapping of a code page needs to be wback+inv so that
         *             icache fetch by userspace sees code correctly.
         * !EXEC page: If K-mapping is NOT congruent to U-mapping, flush it
         *             so userspace sees the right data.
         *  (Avoids the flush for Non-exec + congruent mapping case)
         */
        if ((vma->vm_flags & VM_EXEC) ||
             addr_not_cache_congruent(paddr, vaddr)) {

                int dirty = !test_and_set_bit(PG_dc_clean, &page->flags);
                if (dirty) {
                        /* wback + inv dcache lines */
                        __flush_dcache_page(paddr, paddr);

                        /* invalidate any existing icache lines */
                        if (vma->vm_flags & VM_EXEC)
                                __inv_icache_page(paddr, vaddr);
                }
        }
}

/* Read the Cache Build Confuration Registers, Decode them and save into
 * the cpuinfo structure for later use.
 * No Validation is done here, simply read/convert the BCRs
 */
void read_decode_mmu_bcr(void)
{
        struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;
        unsigned int tmp;
        struct bcr_mmu_1_2 {
#ifdef CONFIG_CPU_BIG_ENDIAN
                unsigned int ver:8, ways:4, sets:4, u_itlb:8, u_dtlb:8;
#else
                unsigned int u_dtlb:8, u_itlb:8, sets:4, ways:4, ver:8;
#endif
        } *mmu2;

        struct bcr_mmu_3 {
#ifdef CONFIG_CPU_BIG_ENDIAN
        unsigned int ver:8, ways:4, sets:4, osm:1, reserv:3, pg_sz:4,
                     u_itlb:4, u_dtlb:4;
#else
        unsigned int u_dtlb:4, u_itlb:4, pg_sz:4, reserv:3, osm:1, sets:4,
                     ways:4, ver:8;
#endif
        } *mmu3;

        tmp = read_aux_reg(ARC_REG_MMU_BCR);
        mmu->ver = (tmp >> 24);

        if (mmu->ver <= 2) {
                mmu2 = (struct bcr_mmu_1_2 *)&tmp;
                mmu->pg_sz = PAGE_SIZE;
                mmu->sets = 1 << mmu2->sets;
                mmu->ways = 1 << mmu2->ways;
                mmu->u_dtlb = mmu2->u_dtlb;
                mmu->u_itlb = mmu2->u_itlb;
        } else {
                mmu3 = (struct bcr_mmu_3 *)&tmp;
                mmu->pg_sz = 512 << mmu3->pg_sz;
                mmu->sets = 1 << mmu3->sets;
                mmu->ways = 1 << mmu3->ways;
                mmu->u_dtlb = mmu3->u_dtlb;
                mmu->u_itlb = mmu3->u_itlb;
        }

        mmu->num_tlb = mmu->sets * mmu->ways;
}

char *arc_mmu_mumbojumbo(int cpu_id, char *buf, int len)
{
        int n = 0;
        struct cpuinfo_arc_mmu *p_mmu = &cpuinfo_arc700[cpu_id].mmu;

        n += scnprintf(buf + n, len - n, "ARC700 MMU [v%x]\t: %dk PAGE, ",
                       p_mmu->ver, TO_KB(p_mmu->pg_sz));

        n += scnprintf(buf + n, len - n,
                       "J-TLB %d (%dx%d), uDTLB %d, uITLB %d, %s\n",
                       p_mmu->num_tlb, p_mmu->sets, p_mmu->ways,
                       p_mmu->u_dtlb, p_mmu->u_itlb,
                       IS_ENABLED(CONFIG_ARC_MMU_SASID) ? "SASID" : "");

        return buf;
}

void arc_mmu_init(void)
{
        char str[256];
        struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;

        printk(arc_mmu_mumbojumbo(0, str, sizeof(str)));

        /* For efficiency sake, kernel is compile time built for a MMU ver
         * This must match the hardware it is running on.
         * Linux built for MMU V2, if run on MMU V1 will break down because V1
         *  hardware doesn't understand cmds such as WriteNI, or IVUTLB
         * On the other hand, Linux built for V1 if run on MMU V2 will do
         *   un-needed workarounds to prevent memcpy thrashing.
         * Similarly MMU V3 has new features which won't work on older MMU
         */
        if (mmu->ver != CONFIG_ARC_MMU_VER) {
                panic("MMU ver %d doesn't match kernel built for %d...\n",
                      mmu->ver, CONFIG_ARC_MMU_VER);
        }

        if (mmu->pg_sz != PAGE_SIZE)
                panic("MMU pg size != PAGE_SIZE (%luk)\n", TO_KB(PAGE_SIZE));

        /* Enable the MMU */
        write_aux_reg(ARC_REG_PID, MMU_ENABLE);

        /* In smp we use this reg for interrupt 1 scratch */
#ifndef CONFIG_SMP
        /* swapper_pg_dir is the pgd for the kernel, used by vmalloc */
        write_aux_reg(ARC_REG_SCRATCH_DATA0, swapper_pg_dir);
#endif
}

/*
 * TLB Programmer's Model uses Linear Indexes: 0 to {255, 511} for 128 x {2,4}
 * The mapping is Column-first.
 *              ---------------------   -----------
 *              |way0|way1|way2|way3|   |way0|way1|
 *              ---------------------   -----------
 * [set0]       |  0 |  1 |  2 |  3 |   |  0 |  1 |
 * [set1]       |  4 |  5 |  6 |  7 |   |  2 |  3 |
 *              ~                   ~   ~         ~
 * [set127]     | 508| 509| 510| 511|   | 254| 255|
 *              ---------------------   -----------
 * For normal operations we don't(must not) care how above works since
 * MMU cmd getIndex(vaddr) abstracts that out.
 * However for walking WAYS of a SET, we need to know this
 */
#define SET_WAY_TO_IDX(mmu, set, way)  ((set) * mmu->ways + (way))

/* Handling of Duplicate PD (TLB entry) in MMU.
 * -Could be due to buggy customer tapeouts or obscure kernel bugs
 * -MMU complaints not at the time of duplicate PD installation, but at the
 *      time of lookup matching multiple ways.
 * -Ideally these should never happen - but if they do - workaround by deleting
 *      the duplicate one.
 * -Knob to be verbose abt it.(TODO: hook them up to debugfs)
 */
volatile int dup_pd_verbose = 1;/* Be slient abt it or complain (default) */

void do_tlb_overlap_fault(unsigned long cause, unsigned long address,
                          struct pt_regs *regs)
{
        int set, way, n;
        unsigned int pd0[4], pd1[4];    /* assume max 4 ways */
        unsigned long flags, is_valid;
        struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;

        local_irq_save(flags);

        /* re-enable the MMU */
        write_aux_reg(ARC_REG_PID, MMU_ENABLE | read_aux_reg(ARC_REG_PID));

        /* loop thru all sets of TLB */
        for (set = 0; set < mmu->sets; set++) {

                /* read out all the ways of current set */
                for (way = 0, is_valid = 0; way < mmu->ways; way++) {
                        write_aux_reg(ARC_REG_TLBINDEX,
                                          SET_WAY_TO_IDX(mmu, set, way));
                        write_aux_reg(ARC_REG_TLBCOMMAND, TLBRead);
                        pd0[way] = read_aux_reg(ARC_REG_TLBPD0);
                        pd1[way] = read_aux_reg(ARC_REG_TLBPD1);
                        is_valid |= pd0[way] & _PAGE_PRESENT;
                }

                /* If all the WAYS in SET are empty, skip to next SET */
                if (!is_valid)
                        continue;

                /* Scan the set for duplicate ways: needs a nested loop */
                for (way = 0; way < mmu->ways; way++) {
                        if (!pd0[way])
                                continue;

                        for (n = way + 1; n < mmu->ways; n++) {
                                if ((pd0[way] & PAGE_MASK) ==
                                    (pd0[n] & PAGE_MASK)) {

                                        if (dup_pd_verbose) {
                                                pr_info("Duplicate PD's @"
                                                        "[%d:%d]/[%d:%d]\n",
                                                     set, way, set, n);
                                                pr_info("TLBPD0[%u]: %08x\n",
                                                     way, pd0[way]);
                                        }

                                        /*
                                         * clear entry @way and not @n. This is
                                         * critical to our optimised loop
                                         */
                                        pd0[way] = pd1[way] = 0;
                                        write_aux_reg(ARC_REG_TLBINDEX,
                                                SET_WAY_TO_IDX(mmu, set, way));
                                        __tlb_entry_erase();
                                }
                        }
                }
        }

        local_irq_restore(flags);
}

/***********************************************************************
 * Diagnostic Routines
 *  -Called from Low Level TLB Hanlders if things don;t look good
 **********************************************************************/

#ifdef CONFIG_ARC_DBG_TLB_PARANOIA

/*
 * Low Level ASM TLB handler calls this if it finds that HW and SW ASIDS
 * don't match
 */
void print_asid_mismatch(int is_fast_path)
{
        int pid_sw, pid_hw;
        pid_sw = current->active_mm->context.asid;
        pid_hw = read_aux_reg(ARC_REG_PID) & 0xff;

        pr_emerg("ASID Mismatch in %s Path Handler: sw-pid=0x%x hw-pid=0x%x\n",
               is_fast_path ? "Fast" : "Slow", pid_sw, pid_hw);

        __asm__ __volatile__("flag 1");
}

void tlb_paranoid_check(unsigned int pid_sw, unsigned long addr)
{
        unsigned int pid_hw;

        pid_hw = read_aux_reg(ARC_REG_PID) & 0xff;

        if (addr < 0x70000000 && ((pid_hw != pid_sw) || (pid_sw == NO_ASID)))
                print_asid_mismatch(0);
}
#endif