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Diffstat (limited to 'arch/arc/mm/tlb.c')
| -rw-r--r-- | arch/arc/mm/tlb.c | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c index 404e5be4f70..232a0ff80a5 100644 --- a/arch/arc/mm/tlb.c +++ b/arch/arc/mm/tlb.c @@ -6,13 +6,97 @@ * 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 <asm/arcregs.h> +#include <asm/setup.h> #include <asm/mmu_context.h> #include <asm/tlb.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; @@ -22,6 +106,233 @@ int asid_cache = FIRST_ASID; */ struct mm_struct *asid_mm_map[NUM_ASID + 1]; +/* + * Utility Routine to erase a J-TLB entry + * The procedure is to look it up in the MMU. If found, ERASE it by + * issuing a TlbWrite CMD with PD0 = PD1 = 0 + */ + +static 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 void tlb_entry_erase(unsigned int vaddr_n_asid) +{ + unsigned int idx; + + /* Locate the TLB entry for this vaddr + ASID */ + write_aux_reg(ARC_REG_TLBPD0, vaddr_n_asid); + write_aux_reg(ARC_REG_TLBCOMMAND, TLBProbe); + idx = read_aux_reg(ARC_REG_TLBINDEX); + + /* No error means entry found, zero it out */ + if (likely(!(idx & TLB_LKUP_ERR))) { + __tlb_entry_erase(); + } else { /* Some sort of Error */ + + /* Duplicate entry error */ + if (idx & 0x1) { + /* TODO we need to handle this case too */ + pr_emerg("unhandled Duplicate flush for %x\n", + vaddr_n_asid); + } + /* else entry not found so nothing to do */ + } +} + +/**************************************************************************** + * 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 < 3) + /* 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 + +} + +/* + * 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 |