Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

[mirror_ubuntu-artful-kernel.git] / arch / arc / mm / cache.c

/*
 * ARC Cache Management
 *
 * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
 * 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.
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/cache.h>
#include <linux/mmu_context.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#include <linux/pagemap.h>
#include <asm/cacheflush.h>
#include <asm/cachectl.h>
#include <asm/setup.h>

static int l2_line_sz;
static int ioc_exists;
int slc_enable = 1, ioc_enable = 1;
unsigned long perip_base = ARC_UNCACHED_ADDR_SPACE; /* legacy value for boot */
unsigned long perip_end = 0xFFFFFFFF; /* legacy value */

void (*_cache_line_loop_ic_fn)(phys_addr_t paddr, unsigned long vaddr,
                               unsigned long sz, const int cacheop);

void (*__dma_cache_wback_inv)(phys_addr_t start, unsigned long sz);
void (*__dma_cache_inv)(phys_addr_t start, unsigned long sz);
void (*__dma_cache_wback)(phys_addr_t start, unsigned long sz);

char *arc_cache_mumbojumbo(int c, char *buf, int len)
{
        int n = 0;
        struct cpuinfo_arc_cache *p;

#define PR_CACHE(p, cfg, str)                                           \
        if (!(p)->line_len)                                             \
                n += scnprintf(buf + n, len - n, str"\t\t: N/A\n");     \
        else                                                            \
                n += scnprintf(buf + n, len - n,                        \
                        str"\t\t: %uK, %dway/set, %uB Line, %s%s%s\n",  \
                        (p)->sz_k, (p)->assoc, (p)->line_len,           \
                        (p)->vipt ? "VIPT" : "PIPT",                    \
                        (p)->alias ? " aliasing" : "",                  \
                        IS_USED_CFG(cfg));

        PR_CACHE(&cpuinfo_arc700[c].icache, CONFIG_ARC_HAS_ICACHE, "I-Cache");
        PR_CACHE(&cpuinfo_arc700[c].dcache, CONFIG_ARC_HAS_DCACHE, "D-Cache");

        p = &cpuinfo_arc700[c].slc;
        if (p->line_len)
                n += scnprintf(buf + n, len - n,
                               "SLC\t\t: %uK, %uB Line%s\n",
                               p->sz_k, p->line_len, IS_USED_RUN(slc_enable));

        n += scnprintf(buf + n, len - n, "Peripherals\t: %#lx%s%s\n",
                       perip_base,
                       IS_AVAIL3(ioc_exists, ioc_enable, ", IO-Coherency "));

        return buf;
}

/*
 * Read the Cache Build Confuration Registers, Decode them and save into
 * the cpuinfo structure for later use.
 * No Validation done here, simply read/convert the BCRs
 */
static void read_decode_cache_bcr_arcv2(int cpu)
{
        struct cpuinfo_arc_cache *p_slc = &cpuinfo_arc700[cpu].slc;
        struct bcr_generic sbcr;

        struct bcr_slc_cfg {
#ifdef CONFIG_CPU_BIG_ENDIAN
                unsigned int pad:24, way:2, lsz:2, sz:4;
#else
                unsigned int sz:4, lsz:2, way:2, pad:24;
#endif
        } slc_cfg;

        struct bcr_clust_cfg {
#ifdef CONFIG_CPU_BIG_ENDIAN
                unsigned int pad:7, c:1, num_entries:8, num_cores:8, ver:8;
#else
                unsigned int ver:8, num_cores:8, num_entries:8, c:1, pad:7;
#endif
        } cbcr;

        struct bcr_volatile {
#ifdef CONFIG_CPU_BIG_ENDIAN
                unsigned int start:4, limit:4, pad:22, order:1, disable:1;
#else
                unsigned int disable:1, order:1, pad:22, limit:4, start:4;
#endif
        } vol;


        READ_BCR(ARC_REG_SLC_BCR, sbcr);
        if (sbcr.ver) {
                READ_BCR(ARC_REG_SLC_CFG, slc_cfg);
                p_slc->sz_k = 128 << slc_cfg.sz;
                l2_line_sz = p_slc->line_len = (slc_cfg.lsz == 0) ? 128 : 64;
        }

        READ_BCR(ARC_REG_CLUSTER_BCR, cbcr);
        if (cbcr.c)
                ioc_exists = 1;
        else
                ioc_enable = 0;

        /* HS 2.0 didn't have AUX_VOL */
        if (cpuinfo_arc700[cpu].core.family > 0x51) {
                READ_BCR(AUX_VOL, vol);
                perip_base = vol.start << 28;
                /* HS 3.0 has limit and strict-ordering fields */
                if (cpuinfo_arc700[cpu].core.family > 0x52)
                        perip_end = (vol.limit << 28) - 1;
        }
}

void read_decode_cache_bcr(void)
{
        struct cpuinfo_arc_cache *p_ic, *p_dc;
        unsigned int cpu = smp_processor_id();
        struct bcr_cache {
#ifdef CONFIG_CPU_BIG_ENDIAN
                unsigned int pad:12, line_len:4, sz:4, config:4, ver:8;
#else
                unsigned int ver:8, config:4, sz:4, line_len:4, pad:12;
#endif
        } ibcr, dbcr;

        p_ic = &cpuinfo_arc700[cpu].icache;
        READ_BCR(ARC_REG_IC_BCR, ibcr);

        if (!ibcr.ver)
                goto dc_chk;

        if (ibcr.ver <= 3) {
                BUG_ON(ibcr.config != 3);
                p_ic->assoc = 2;                /* Fixed to 2w set assoc */
        } else if (ibcr.ver >= 4) {
                p_ic->assoc = 1 << ibcr.config; /* 1,2,4,8 */
        }

        p_ic->line_len = 8 << ibcr.line_len;
        p_ic->sz_k = 1 << (ibcr.sz - 1);
        p_ic->vipt = 1;
        p_ic->alias = p_ic->sz_k/p_ic->assoc/TO_KB(PAGE_SIZE) > 1;

dc_chk:
        p_dc = &cpuinfo_arc700[cpu].dcache;
        READ_BCR(ARC_REG_DC_BCR, dbcr);

        if (!dbcr.ver)
                goto slc_chk;

        if (dbcr.ver <= 3) {
                BUG_ON(dbcr.config != 2);
                p_dc->assoc = 4;                /* Fixed to 4w set assoc */
                p_dc->vipt = 1;
                p_dc->alias = p_dc->sz_k/p_dc->assoc/TO_KB(PAGE_SIZE) > 1;
        } else if (dbcr.ver >= 4) {
                p_dc->assoc = 1 << dbcr.config; /* 1,2,4,8 */
                p_dc->vipt = 0;
                p_dc->alias = 0;                /* PIPT so can't VIPT alias */
        }

        p_dc->line_len = 16 << dbcr.line_len;
        p_dc->sz_k = 1 << (dbcr.sz - 1);

slc_chk:
        if (is_isa_arcv2())
                read_decode_cache_bcr_arcv2(cpu);
}

/*
 * Line Operation on {I,D}-Cache
 */

#define OP_INV          0x1
#define OP_FLUSH        0x2
#define OP_FLUSH_N_INV  0x3
#define OP_INV_IC       0x4

/*
 *              I-Cache Aliasing in ARC700 VIPT caches (MMU v1-v3)
 *
 * ARC VIPT I-cache uses vaddr to index into cache and paddr to match the tag.
 * The orig Cache Management Module "CDU" only required paddr to invalidate a
 * certain line since it sufficed as index in Non-Aliasing VIPT cache-geometry.
 * Infact for distinct V1,V2,P: all of {V1-P},{V2-P},{P-P} would end up fetching
 * the exact same line.
 *
 * However for larger Caches (way-size > page-size) - i.e. in Aliasing config,
 * paddr alone could not be used to correctly index the cache.
 *
 * ------------------
 * MMU v1/v2 (Fixed Page Size 8k)
 * ------------------
 * The solution was to provide CDU with these additonal vaddr bits. These
 * would be bits [x:13], x would depend on cache-geometry, 13 comes from
 * standard page size of 8k.
 * H/w folks chose [17:13] to be a future safe range, and moreso these 5 bits
 * of vaddr could easily be "stuffed" in the paddr as bits [4:0] since the
 * orig 5 bits of paddr were anyways ignored by CDU line ops, as they
 * represent the offset within cache-line. The adv of using this "clumsy"
 * interface for additional info was no new reg was needed in CDU programming
 * model.
 *
 * 17:13 represented the max num of bits passable, actual bits needed were
 * fewer, based on the num-of-aliases possible.
 * -for 2 alias possibility, only bit 13 needed (32K cache)
 * -for 4 alias possibility, bits 14:13 needed (64K cache)
 *
 * ------------------
 * MMU v3
 * ------------------
 * This ver of MMU supports variable page sizes (1k-16k): although Linux will
 * only support 8k (default), 16k and 4k.
 * However from hardware perspective, smaller page sizes aggravate aliasing
 * meaning more vaddr bits needed to disambiguate the cache-line-op ;
 * the existing scheme of piggybacking won't work for certain configurations.
 * Two new registers IC_PTAG and DC_PTAG inttoduced.
 * "tag" bits are provided in PTAG, index bits in existing IVIL/IVDL/FLDL regs
 */

static inline
void __cache_line_loop_v2(phys_addr_t paddr, unsigned long vaddr,
                          unsigned long sz, const int op)
{
        unsigned int aux_cmd;
        int num_lines;
        const int full_page = __builtin_constant_p(sz) && sz == PAGE_SIZE;

        if (op == OP_INV_IC) {
                aux_cmd = ARC_REG_IC_IVIL;
        } else {
                /* d$ cmd: INV (discard or wback-n-discard) OR FLUSH (wback) */
                aux_cmd = op & OP_INV ? ARC_REG_DC_IVDL : ARC_REG_DC_FLDL;
        }

        /* Ensure we properly floor/ceil the non-line aligned/sized requests
         * and have @paddr - aligned to cache line and integral @num_lines.
         * This however can be avoided for page sized since:
         *  -@paddr will be cache-line aligned already (being page aligned)
         *  -@sz will be integral multiple of line size (being page sized).
         */
        if (!full_page) {
                sz += paddr & ~CACHE_LINE_MASK;
                paddr &= CACHE_LINE_MASK;
                vaddr &= CACHE_LINE_MASK;
        }

        num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);

        /* MMUv2 and before: paddr contains stuffed vaddrs bits */
        paddr |= (vaddr >> PAGE_SHIFT) & 0x1F;

        while (num_lines-- > 0) {
                write_aux_reg(aux_cmd, paddr);
                paddr += L1_CACHE_BYTES;
        }
}

/*
 * For ARC700 MMUv3 I-cache and D-cache flushes
 *  - ARC700 programming model requires paddr and vaddr be passed in seperate
 *    AUX registers (*_IV*L and *_PTAG respectively) irrespective of whether the
 *    caches actually alias or not.
 * -  For HS38, only the aliasing I-cache configuration uses the PTAG reg
 *    (non aliasing I-cache version doesn't; while D-cache can't possibly alias)
 */
static inline
void __cache_line_loop_v3(phys_addr_t paddr, unsigned long vaddr,
                          unsigned long sz, const int op)
{
        unsigned int aux_cmd, aux_tag;
        int num_lines;
        const int full_page = __builtin_constant_p(sz) && sz == PAGE_SIZE;

        if (op == OP_INV_IC) {
                aux_cmd = ARC_REG_IC_IVIL;
                aux_tag = ARC_REG_IC_PTAG;
        } else {
                aux_cmd = op & OP_INV ? ARC_REG_DC_IVDL : ARC_REG_DC_FLDL;
                aux_tag = ARC_REG_DC_PTAG;
        }

        /* Ensure we properly floor/ceil the non-line aligned/sized requests
         * and have @paddr - aligned to cache line and integral @num_lines.
         * This however can be avoided for page sized since:
         *  -@paddr will be cache-line aligned already (being page aligned)
         *  -@sz will be integral multiple of line size (being page sized).
         */
        if (!full_page) {
                sz += paddr & ~CACHE_LINE_MASK;
                paddr &= CACHE_LINE_MASK;
                vaddr &= CACHE_LINE_MASK;
        }
        num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);

        /*
         * MMUv3, cache ops require paddr in PTAG reg
         * if V-P const for loop, PTAG can be written once outside loop
         */
        if (full_page)
                write_aux_reg(aux_tag, paddr);

        /*
         * This is technically for MMU v4, using the MMU v3 programming model
         * Special work for HS38 aliasing I-cache configuration with PAE40
         *   - upper 8 bits of paddr need to be written into PTAG_HI
         *   - (and needs to be written before the lower 32 bits)
         * Note that PTAG_HI is hoisted outside the line loop
         */
        if (is_pae40_enabled() && op == OP_INV_IC)
                write_aux_reg(ARC_REG_IC_PTAG_HI, (u64)paddr >> 32);

        while (num_lines-- > 0) {
                if (!full_page) {
                        write_aux_reg(aux_tag, paddr);
                        paddr += L1_CACHE_BYTES;
                }

                write_aux_reg(aux_cmd, vaddr);
                vaddr += L1_CACHE_BYTES;
        }
}

/*
 * In HS38x (MMU v4), I-cache is VIPT (can alias), D-cache is PIPT
 * Here's how cache ops are implemented
 *
 *  - D-cache: only paddr needed (in DC_IVDL/DC_FLDL)
 *  - I-cache Non Aliasing: Despite VIPT, only paddr needed (in IC_IVIL)
 *  - I-cache Aliasing: Both vaddr and paddr needed (in IC_IVIL, IC_PTAG
 *    respectively, similar to MMU v3 programming model, hence
 *    __cache_line_loop_v3() is used)
 *
 * If PAE40 is enabled, independent of aliasing considerations, the higher bits
 * needs to be written into PTAG_HI
 */
static inline
void __cache_line_loop_v4(phys_addr_t paddr, unsigned long vaddr,
                          unsigned long sz, const int cacheop)
{
        unsigned int aux_cmd;
        int num_lines;
        const int full_page_op = __builtin_constant_p(sz) && sz == PAGE_SIZE;

        if (cacheop == OP_INV_IC) {
                aux_cmd = ARC_REG_IC_IVIL;
        } else {
                /* d$ cmd: INV (discard or wback-n-discard) OR FLUSH (wback) */
                aux_cmd = cacheop & OP_INV ? ARC_REG_DC_IVDL : ARC_REG_DC_FLDL;
        }

        /* Ensure we properly floor/ceil the non-line aligned/sized requests
         * and have @paddr - aligned to cache line and integral @num_lines.
         * This however can be avoided for page sized since:
         *  -@paddr will be cache-line aligned already (being page aligned)
         *  -@sz will be integral multiple of line size (being page sized).
         */
        if (!full_page_op) {
                sz += paddr & ~CACHE_LINE_MASK;
                paddr &= CACHE_LINE_MASK;
        }

        num_lines = DIV_ROUND_UP(sz, L1_CACHE_BYTES);

        /*
         * For HS38 PAE40 configuration
         *   - upper 8 bits of paddr need to be written into PTAG_HI
         *   - (and needs to be written before the lower 32 bits)
         */
        if (is_pae40_enabled()) {
                if (cacheop == OP_INV_IC)
                        /*
                         * Non aliasing I-cache in HS38,
                         * aliasing I-cache handled in __cache_line_loop_v3()
                         */
                        write_aux_reg(ARC_REG_IC_PTAG_HI, (u64)paddr >> 32);
                else
                        write_aux_reg(ARC_REG_DC_PTAG_HI, (u64)paddr >> 32);
        }

        while (num_lines-- > 0) {
                write_aux_reg(aux_cmd, paddr);
                paddr += L1_CACHE_BYTES;
        }
}

#if (CONFIG_ARC_MMU_VER < 3)
#define __cache_line_loop       __cache_line_loop_v2
#elif (CONFIG_ARC_MMU_VER == 3)
#define __cache_line_loop       __cache_line_loop_v3
#elif (CONFIG_ARC_MMU_VER > 3)
#define __cache_line_loop       __cache_line_loop_v4
#endif

#ifdef CONFIG_ARC_HAS_DCACHE

/***************************************************************
 * Machine specific helpers for Entire D-Cache or Per Line ops
 */

static inline void __before_dc_op(const int op)
{
        if (op == OP_FLUSH_N_INV) {
                /* Dcache provides 2 cmd: FLUSH or INV
                 * INV inturn has sub-modes: DISCARD or FLUSH-BEFORE
                 * flush-n-inv is achieved by INV cmd but with IM=1
                 * So toggle INV sub-mode depending on op request and default
                 */
                const unsigned int ctl = ARC_REG_DC_CTRL;
                write_aux_reg(ctl, read_aux_reg(ctl) | DC_CTRL_INV_MODE_FLUSH);
        }
}

static inline void __after_dc_op(const int op)
{
        if (op & OP_FLUSH) {
                const unsigned int ctl = ARC_REG_DC_CTRL;
                unsigned int reg;

                /* flush / flush-n-inv both wait */
                while ((reg = read_aux_reg(ctl)) & DC_CTRL_FLUSH_STATUS)
                        ;

                /* Switch back to default Invalidate mode */
                if (op == OP_FLUSH_N_INV)
                        write_aux_reg(ctl, reg & ~DC_CTRL_INV_MODE_FLUSH);
        }
}

/*
 * Operation on Entire D-Cache
 * @op = {OP_INV, OP_FLUSH, OP_FLUSH_N_INV}
 * Note that constant propagation ensures all the checks are gone
 * in generated code
 */
static inline void __dc_entire_op(const int op)
{
        int aux;

        __before_dc_op(op);

        if (op & OP_INV)        /* Inv or flush-n-inv use same cmd reg */
                aux = ARC_REG_DC_IVDC;
        else
                aux = ARC_REG_DC_FLSH;

        write_aux_reg(aux, 0x1);

        __after_dc_op(op);
}

static inline void __dc_disable(void)
{
        const int r = ARC_REG_DC_CTRL;

        __dc_entire_op(OP_FLUSH_N_INV);
        write_aux_reg(r, read_aux_reg(r) | DC_CTRL_DIS);
}

static void __dc_enable(void)
{
        const int r = ARC_REG_DC_CTRL;

        write_aux_reg(r, read_aux_reg(r) & ~DC_CTRL_DIS);
}

/* For kernel mappings cache operation: index is same as paddr */
#define __dc_line_op_k(p, sz, op)       __dc_line_op(p, p, sz, op)

/*
 * D-Cache Line ops: Per Line INV (discard or wback+discard) or FLUSH (wback)
 */
static inline void __dc_line_op(phys_addr_t paddr, unsigned long vaddr,
                                unsigned long sz, const int op)
{
        unsigned long flags;

        local_irq_save(flags);

        __before_dc_op(op);

        __cache_line_loop(paddr, vaddr, sz, op);

        __after_dc_op(op);

        local_irq_restore(flags);
}

#else

#define __dc_entire_op(op)
#define __dc_disable()
#define __dc_enable()
#define __dc_line_op(paddr, vaddr, sz, op)
#define __dc_line_op_k(paddr, sz, op)

#endif /* CONFIG_ARC_HAS_DCACHE */

#ifdef CONFIG_ARC_HAS_ICACHE

static inline void __ic_entire_inv(void)
{
        write_aux_reg(ARC_REG_IC_IVIC, 1);
        read_aux_reg(ARC_REG_IC_CTRL);  /* blocks */
}

static inline void
__ic_line_inv_vaddr_local(phys_addr_t paddr, unsigned long vaddr,
                          unsigned long sz)
{
        unsigned long flags;

        local_irq_save(flags);
        (*_cache_line_loop_ic_fn)(paddr, vaddr, sz, OP_INV_IC);
        local_irq_restore(flags);
}

#ifndef CONFIG_SMP

#define __ic_line_inv_vaddr(p, v, s)    __ic_line_inv_vaddr_local(p, v, s)

#else

struct ic_inv_args {
        phys_addr_t paddr, vaddr;
        int sz;
};

static void __ic_line_inv_vaddr_helper(void *info)
{
        struct ic_inv_args *ic_inv = info;

        __ic_line_inv_vaddr_local(ic_inv->paddr, ic_inv->vaddr, ic_inv->sz);
}

static void __ic_line_inv_vaddr(phys_addr_t paddr, unsigned long vaddr,
                                unsigned long sz)
{
        struct ic_inv_args ic_inv = {
                .paddr = paddr,
                .vaddr = vaddr,
                .sz    = sz
        };

        on_each_cpu(__ic_line_inv_vaddr_helper, &ic_inv, 1);
}

#endif  /* CONFIG_SMP */

#else   /* !CONFIG_ARC_HAS_ICACHE */

#define __ic_entire_inv()
#define __ic_line_inv_vaddr(pstart, vstart, sz)

#endif /* CONFIG_ARC_HAS_ICACHE */

noinline void slc_op(phys_addr_t paddr, unsigned long sz, const int op)
{
#ifdef CONFIG_ISA_ARCV2
        /*
         * SLC is shared between all cores and concurrent aux operations from
         * multiple cores need to be serialized using a spinlock
         * A concurrent operation can be silently ignored and/or the old/new
         * operation can remain incomplete forever (lockup in SLC_CTRL_BUSY loop
         * below)
         */
        static DEFINE_SPINLOCK(lock);
        unsigned long flags;
        unsigned int ctrl;

        spin_lock_irqsave(&lock, flags);

        /*
         * The Region Flush operation is specified by CTRL.RGN_OP[11..9]
         *  - b'000 (default) is Flush,
         *  - b'001 is Invalidate if CTRL.IM == 0
         *  - b'001 is Flush-n-Invalidate if CTRL.IM == 1
         */
        ctrl = read_aux_reg(ARC_REG_SLC_CTRL);

        /* Don't rely on default value of IM bit */
        if (!(op & OP_FLUSH))           /* i.e. OP_INV */
                ctrl &= ~SLC_CTRL_IM;   /* clear IM: Disable flush before Inv */
        else
                ctrl |= SLC_CTRL_IM;

        if (op & OP_INV)
                ctrl |= SLC_CTRL_RGN_OP_INV;    /* Inv or flush-n-inv */
        else
                ctrl &= ~SLC_CTRL_RGN_OP_INV;

        write_aux_reg(ARC_REG_SLC_CTRL, ctrl);

        /*
         * Lower bits are ignored, no need to clip
         * END needs to be setup before START (latter triggers the operation)
         * END can't be same as START, so add (l2_line_sz - 1) to sz
         */
        write_aux_reg(ARC_REG_SLC_RGN_END, (paddr + sz + l2_line_sz - 1));
        write_aux_reg(ARC_REG_SLC_RGN_START, paddr);

        while (read_aux_reg(ARC_REG_SLC_CTRL) & SLC_CTRL_BUSY);

        spin_unlock_irqrestore(&lock, flags);
#endif
}

noinline static void slc_entire_op(const int op)
{
        unsigned int ctrl, r = ARC_REG_SLC_CTRL;

        ctrl = read_aux_reg(r);

        if (!(op & OP_FLUSH))           /* i.e. OP_INV */
                ctrl &= ~SLC_CTRL_IM;   /* clear IM: Disable flush before Inv */
        else
                ctrl |= SLC_CTRL_IM;

        write_aux_reg(r, ctrl);

        write_aux_reg(ARC_REG_SLC_INVALIDATE, 1);

        /* Make sure "busy" bit reports correct stataus, see STAR 9001165532 */
        read_aux_reg(r);

        /* Important to wait for flush to complete */
        while (read_aux_reg(r) & SLC_CTRL_BUSY);
}

static inline void arc_slc_disable(void)
{
        const int r = ARC_REG_SLC_CTRL;

        slc_entire_op(OP_FLUSH_N_INV);
        write_aux_reg(r, read_aux_reg(r) | SLC_CTRL_DIS);
}

static inline void arc_slc_enable(void)
{
        const int r = ARC_REG_SLC_CTRL;

        write_aux_reg(r, read_aux_reg(r) & ~SLC_CTRL_DIS);
}

/***********************************************************
 * Exported APIs
 */

/*
 * Handle cache congruency of kernel and userspace mappings of page when kernel
 * writes-to/reads-from
 *
 * The idea is to defer flushing of kernel mapping after a WRITE, possible if:
 *  -dcache is NOT aliasing, hence any U/K-mappings of page are congruent
 *  -U-mapping doesn't exist yet for page (finalised in update_mmu_cache)
 *  -In SMP, if hardware caches are coherent
 *
 * There's a corollary case, where kernel READs from a userspace mapped page.
 * If the U-mapping is not congruent to to K-mapping, former needs flushing.
 */
void flush_dcache_page(struct page *page)
{
        struct address_space *mapping;

        if (!cache_is_vipt_aliasing()) {
                clear_bit(PG_dc_clean, &page->flags);
                return;
        }

        /* don't handle anon pages here */
        mapping = page_mapping(page);
        if (!mapping)
                return;

        /*
         * pagecache page, file not yet mapped to userspace
         * Make a note that K-mapping is dirty
         */
        if (!mapping_mapped(mapping)) {
                clear_bit(PG_dc_clean, &page->flags);
        } else if (page_mapcount(page)) {

                /* kernel reading from page with U-mapping */
                phys_addr_t paddr = (unsigned long)page_address(page);
                unsigned long vaddr = page->index << PAGE_SHIFT;

                if (addr_not_cache_congruent(paddr, vaddr))
                        __flush_dcache_page(paddr, vaddr);
        }
}
EXPORT_SYMBOL(flush_dcache_page);

/*
 * DMA ops for systems with L1 cache only
 * Make memory coherent with L1 cache by flushing/invalidating L1 lines
 */
static void __dma_cache_wback_inv_l1(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_FLUSH_N_INV);
}

static void __dma_cache_inv_l1(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_INV);
}

static void __dma_cache_wback_l1(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_FLUSH);
}

/*
 * DMA ops for systems with both L1 and L2 caches, but without IOC
 * Both L1 and L2 lines need to be explicitly flushed/invalidated
 */
static void __dma_cache_wback_inv_slc(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_FLUSH_N_INV);
        slc_op(start, sz, OP_FLUSH_N_INV);
}

static void __dma_cache_inv_slc(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_INV);
        slc_op(start, sz, OP_INV);
}

static void __dma_cache_wback_slc(phys_addr_t start, unsigned long sz)
{
        __dc_line_op_k(start, sz, OP_FLUSH);
        slc_op(start, sz, OP_FLUSH);
}

/*
 * DMA ops for systems with IOC
 * IOC hardware snoops all DMA traffic keeping the caches consistent with
 * memory - eliding need for any explicit cache maintenance of DMA buffers
 */
static void __dma_cache_wback_inv_ioc(phys_addr_t start, unsigned long sz) {}
static void __dma_cache_inv_ioc(phys_addr_t start, unsigned long sz) {}
static void __dma_cache_wback_ioc(phys_addr_t start, unsigned long sz) {}

/*
 * Exported DMA API
 */
void dma_cache_wback_inv(phys_addr_t start, unsigned long sz)
{
        __dma_cache_wback_inv(start, sz);
}
EXPORT_SYMBOL(dma_cache_wback_inv);

void dma_cache_inv(phys_addr_t start, unsigned long sz)
{
        __dma_cache_inv(start, sz);
}
EXPORT_SYMBOL(dma_cache_inv);

void dma_cache_wback(phys_addr_t start, unsigned long sz)
{
        __dma_cache_wback(start, sz);
}
EXPORT_SYMBOL(dma_cache_wback);

/*
 * This is API for making I/D Caches consistent when modifying
 * kernel code (loadable modules, kprobes, kgdb...)
 * This is called on insmod, with kernel virtual address for CODE of
 * the module. ARC cache maintenance ops require PHY address thus we
 * need to convert vmalloc addr to PHY addr
 */
void flush_icache_range(unsigned long kstart, unsigned long kend)
{
        unsigned int tot_sz;

        WARN(kstart < TASK_SIZE, "%s() can't handle user vaddr", __func__);

        /* Shortcut for bigger flush ranges.
         * Here we don't care if this was kernel virtual or phy addr
         */
        tot_sz = kend - kstart;
        if (tot_sz > PAGE_SIZE) {
                flush_cache_all();
                return;
        }

        /* Case: Kernel Phy addr (0x8000_0000 onwards) */
        if (likely(kstart > PAGE_OFFSET)) {
                /*
                 * The 2nd arg despite being paddr will be used to index icache
                 * This is OK since no alternate virtual mappings will exist
                 * given the callers for this case: kprobe/kgdb in built-in
                 * kernel code only.
                 */
                __sync_icache_dcache(kstart, kstart, kend - kstart);
                return;
        }

        /*
         * Case: Kernel Vaddr (0x7000_0000 to 0x7fff_ffff)
         * (1) ARC Cache Maintenance ops only take Phy addr, hence special
         *     handling of kernel vaddr.
         *
         * (2) Despite @tot_sz being < PAGE_SIZE (bigger cases handled already),
         *     it still needs to handle  a 2 page scenario, where the range
         *     straddles across 2 virtual pages and hence need for loop
         */
        while (tot_sz > 0) {
                unsigned int off, sz;
                unsigned long phy, pfn;

                off = kstart % PAGE_SIZE;
                pfn = vmalloc_to_pfn((void *)kstart);
                phy = (pfn << PAGE_SHIFT) + off;
                sz = min_t(unsigned int, tot_sz, PAGE_SIZE - off);
                __sync_icache_dcache(phy, kstart, sz);
                kstart += sz;
                tot_sz -= sz;
        }
}
EXPORT_SYMBOL(flush_icache_range);

/*
 * General purpose helper to make I and D cache lines consistent.
 * @paddr is phy addr of region
 * @vaddr is typically user vaddr (breakpoint) or kernel vaddr (vmalloc)
 *    However in one instance, when called by kprobe (for a breakpt in
 *    builtin kernel code) @vaddr will be paddr only, meaning CDU operation will
 *    use a paddr to index the cache (despite VIPT). This is fine since since a
 *    builtin kernel page will not have any virtual mappings.
 *    kprobe on loadable module will be kernel vaddr.
 */
void __sync_icache_dcache(phys_addr_t paddr, unsigned long vaddr, int len)
{
        __dc_line_op(paddr, vaddr, len, OP_FLUSH_N_INV);
        __ic_line_inv_vaddr(paddr, vaddr, len);
}

/* wrapper to compile time eliminate alignment checks in flush loop */
void __inv_icache_page(phys_addr_t paddr, unsigned long vaddr)
{
        __ic_line_inv_vaddr(paddr, vaddr, PAGE_SIZE);
}

/*
 * wrapper to clearout kernel or userspace mappings of a page
 * For kernel mappings @vaddr == @paddr
 */
void __flush_dcache_page(phys_addr_t paddr, unsigned long vaddr)
{
        __dc_line_op(paddr, vaddr & PAGE_MASK, PAGE_SIZE, OP_FLUSH_N_INV);
}

noinline void flush_cache_all(void)
{
        unsigned long flags;

        local_irq_save(flags);

        __ic_entire_inv();
        __dc_entire_op(OP_FLUSH_N_INV);

        local_irq_restore(flags);

}

#ifdef CONFIG_ARC_CACHE_VIPT_ALIASING

void flush_cache_mm(struct mm_struct *mm)
{
        flush_cache_all();
}

void flush_cache_page(struct vm_area_struct *vma, unsigned long u_vaddr,
                      unsigned long pfn)
{
        unsigned int paddr = pfn << PAGE_SHIFT;

        u_vaddr &= PAGE_MASK;

        __flush_dcache_page(paddr, u_vaddr);

        if (vma->vm_flags & VM_EXEC)
                __inv_icache_page(paddr, u_vaddr);
}

void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
                       unsigned long end)
{
        flush_cache_all();
}

void flush_anon_page(struct vm_area_struct *vma, struct page *page,
                     unsigned long u_vaddr)
{
        /* TBD: do we really need to clear the kernel mapping */
        __flush_dcache_page(page_address(page), u_vaddr);
        __flush_dcache_page(page_address(page), page_address(page));

}

#endif

void copy_user_highpage(struct page *to, struct page *from,
        unsigned long u_vaddr, struct vm_area_struct *vma)
{
        void *kfrom = kmap_atomic(from);
        void *kto = kmap_atomic(to);
        int clean_src_k_mappings = 0;

        /*
         * If SRC page was already mapped in userspace AND it's U-mapping is
         * not congruent with K-mapping, sync former to physical page so that
         * K-mapping in memcpy below, sees the right data
         *
         * Note that while @u_vaddr refers to DST page's userspace vaddr, it is
         * equally valid for SRC page as well
         *
         * For !VIPT cache, all of this gets compiled out as
         * addr_not_cache_congruent() is 0
         */
        if (page_mapcount(from) && addr_not_cache_congruent(kfrom, u_vaddr)) {
                __flush_dcache_page((unsigned long)kfrom, u_vaddr);
                clean_src_k_mappings = 1;
        }

        copy_page(kto, kfrom);

        /*
         * Mark DST page K-mapping as dirty for a later finalization by
         * update_mmu_cache(). Although the finalization could have been done
         * here as well (given that both vaddr/paddr are available).
         * But update_mmu_cache() already has code to do that for other
         * non copied user pages (e.g. read faults which wire in pagecache page
         * directly).
         */
        clear_bit(PG_dc_clean, &to->flags);

        /*
         * if SRC was already usermapped and non-congruent to kernel mapping
         * sync the kernel mapping back to physical page
         */
        if (clean_src_k_mappings) {
                __flush_dcache_page((unsigned long)kfrom, (unsigned long)kfrom);
                set_bit(PG_dc_clean, &from->flags);
        } else {
                clear_bit(PG_dc_clean, &from->flags);
        }

        kunmap_atomic(kto);
        kunmap_atomic(kfrom);
}

void clear_user_page(void *to, unsigned long u_vaddr, struct page *page)
{
        clear_page(to);
        clear_bit(PG_dc_clean, &page->flags);
}


/**********************************************************************
 * Explicit Cache flush request from user space via syscall
 * Needed for JITs which generate code on the fly
 */
SYSCALL_DEFINE3(cacheflush, uint32_t, start, uint32_t, sz, uint32_t, flags)
{
        /* TBD: optimize this */
        flush_cache_all();
        return 0;
}

/*
 * IO-Coherency (IOC) setup rules:
 *
 * 1. Needs to be at system level, so only once by Master core
 *    Non-Masters need not be accessing caches at that time
 *    - They are either HALT_ON_RESET and kick started much later or
 *    - if run on reset, need to ensure that arc_platform_smp_wait_to_boot()
 *      doesn't perturb caches or coherency unit
 *
 * 2. caches (L1 and SLC) need to be purged (flush+inv) before setting up IOC,
 *    otherwise any straggler data might behave strangely post IOC enabling
 *
 * 3. All Caches need to be disabled when setting up IOC to elide any in-flight
 *    Coherency transactions
 */
noinline void __init arc_ioc_setup(void)
{
        unsigned int ap_sz;

        /* Flush + invalidate + disable L1 dcache */
        __dc_disable();

        /* Flush + invalidate SLC */
        if (read_aux_reg(ARC_REG_SLC_BCR))
                slc_entire_op(OP_FLUSH_N_INV);

        /* IOC Aperture start: TDB: handle non default CONFIG_LINUX_LINK_BASE */
        write_aux_reg(ARC_REG_IO_COH_AP0_BASE, 0x80000);

        /*
         * IOC Aperture size:
         *   decoded as 2 ^ (SIZE + 2) KB: so setting 0x11 implies 512M
         * TBD: fix for PGU + 1GB of low mem
         * TBD: fix for PAE
         */
        ap_sz = order_base_2(arc_get_mem_sz()/1024) - 2;
        write_aux_reg(ARC_REG_IO_COH_AP0_SIZE, ap_sz);

        write_aux_reg(ARC_REG_IO_COH_PARTIAL, 1);
        write_aux_reg(ARC_REG_IO_COH_ENABLE, 1);

        /* Re-enable L1 dcache */
        __dc_enable();
}

void __init arc_cache_init_master(void)
{
        unsigned int __maybe_unused cpu = smp_processor_id();

        if (IS_ENABLED(CONFIG_ARC_HAS_ICACHE)) {
                struct cpuinfo_arc_cache *ic = &cpuinfo_arc700[cpu].icache;

                if (!ic->line_len)
                        panic("cache support enabled but non-existent cache\n");

                if (ic->line_len != L1_CACHE_BYTES)
                        panic("ICache line [%d] != kernel Config [%d]",
                              ic->line_len, L1_CACHE_BYTES);

                /*
                 * In MMU v4 (HS38x) the aliasing icache config uses IVIL/PTAG
                 * pair to provide vaddr/paddr respectively, just as in MMU v3
                 */
                if (is_isa_arcv2() && ic->alias)
                        _cache_line_loop_ic_fn = __cache_line_loop_v3;
                else
                        _cache_line_loop_ic_fn = __cache_line_loop;
        }

        if (IS_ENABLED(CONFIG_ARC_HAS_DCACHE)) {
                struct cpuinfo_arc_cache *dc = &cpuinfo_arc700[cpu].dcache;

                if (!dc->line_len)
                        panic("cache support enabled but non-existent cache\n");

                if (dc->line_len != L1_CACHE_BYTES)
                        panic("DCache line [%d] != kernel Config [%d]",
                              dc->line_len, L1_CACHE_BYTES);

                /* check for D-Cache aliasing on ARCompact: ARCv2 has PIPT */
                if (is_isa_arcompact()) {
                        int handled = IS_ENABLED(CONFIG_ARC_CACHE_VIPT_ALIASING);
                        int num_colors = dc->sz_k/dc->assoc/TO_KB(PAGE_SIZE);

                        if (dc->alias) {
                                if (!handled)
                                        panic("Enable CONFIG_ARC_CACHE_VIPT_ALIASING\n");
                                if (CACHE_COLORS_NUM != num_colors)
                                        panic("CACHE_COLORS_NUM not optimized for config\n");
                        } else if (!dc->alias && handled) {
                                panic("Disable CONFIG_ARC_CACHE_VIPT_ALIASING\n");
                        }
                }
        }

        /* Note that SLC disable not formally supported till HS 3.0 */
        if (is_isa_arcv2() && l2_line_sz && !slc_enable)
                arc_slc_disable();

        if (is_isa_arcv2() && ioc_enable)
                arc_ioc_setup();

        if (is_isa_arcv2() && ioc_enable) {
                __dma_cache_wback_inv = __dma_cache_wback_inv_ioc;
                __dma_cache_inv = __dma_cache_inv_ioc;
                __dma_cache_wback = __dma_cache_wback_ioc;
        } else if (is_isa_arcv2() && l2_line_sz && slc_enable) {
                __dma_cache_wback_inv = __dma_cache_wback_inv_slc;
                __dma_cache_inv = __dma_cache_inv_slc;
                __dma_cache_wback = __dma_cache_wback_slc;
        } else {
                __dma_cache_wback_inv = __dma_cache_wback_inv_l1;
                __dma_cache_inv = __dma_cache_inv_l1;
                __dma_cache_wback = __dma_cache_wback_l1;
        }
}

void __ref arc_cache_init(void)
{
        unsigned int __maybe_unused cpu = smp_processor_id();
        char str[256];

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

        /*
         * Only master CPU needs to execute rest of function:
         *  - Assume SMP so all cores will have same cache config so
         *    any geomtry checks will be same for all
         *  - IOC setup / dma callbacks only need to be setup once
         */
        if (!cpu)
                arc_cache_init_master();
}