// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2005-2017 Andes Technology Corporation

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/dma-noncoherent.h>
#include <linux/io.h>
#include <linux/cache.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/proc-fns.h>

/*
 * This is the page table (2MB) covering uncached, DMA consistent allocations
 */
static pte_t *consistent_pte;
static DEFINE_RAW_SPINLOCK(consistent_lock);

/*
 * VM region handling support.
 *
 * This should become something generic, handling VM region allocations for
 * vmalloc and similar (ioremap, module space, etc).
 *
 * I envisage vmalloc()'s supporting vm_struct becoming:
 *
 *  struct vm_struct {
 *    struct vm_region  region;
 *    unsigned long     flags;
 *    struct page       **pages;
 *    unsigned int      nr_pages;
 *    unsigned long     phys_addr;
 *  };
 *
 * get_vm_area() would then call vm_region_alloc with an appropriate
 * struct vm_region head (eg):
 *
 *  struct vm_region vmalloc_head = {
 *      .vm_list        = LIST_HEAD_INIT(vmalloc_head.vm_list),
 *      .vm_start       = VMALLOC_START,
 *      .vm_end         = VMALLOC_END,
 *  };
 *
 * However, vmalloc_head.vm_start is variable (typically, it is dependent on
 * the amount of RAM found at boot time.)  I would imagine that get_vm_area()
 * would have to initialise this each time prior to calling vm_region_alloc().
 */
struct arch_vm_region {
        struct list_head vm_list;
        unsigned long vm_start;
        unsigned long vm_end;
        struct page *vm_pages;
};

static struct arch_vm_region consistent_head = {
        .vm_list = LIST_HEAD_INIT(consistent_head.vm_list),
        .vm_start = CONSISTENT_BASE,
        .vm_end = CONSISTENT_END,
};

static struct arch_vm_region *vm_region_alloc(struct arch_vm_region *head,
                                              size_t size, int gfp)
{
        unsigned long addr = head->vm_start, end = head->vm_end - size;
        unsigned long flags;
        struct arch_vm_region *c, *new;

        new = kmalloc(sizeof(struct arch_vm_region), gfp);
        if (!new)
                goto out;

        raw_spin_lock_irqsave(&consistent_lock, flags);

        list_for_each_entry(c, &head->vm_list, vm_list) {
                if ((addr + size) < addr)
                        goto nospc;
                if ((addr + size) <= c->vm_start)
                        goto found;
                addr = c->vm_end;
                if (addr > end)
                        goto nospc;
        }

found:
        /*
         * Insert this entry _before_ the one we found.
         */
        list_add_tail(&new->vm_list, &c->vm_list);
        new->vm_start = addr;
        new->vm_end = addr + size;

        raw_spin_unlock_irqrestore(&consistent_lock, flags);
        return new;

nospc:
        raw_spin_unlock_irqrestore(&consistent_lock, flags);
        kfree(new);
out:
        return NULL;
}

static struct arch_vm_region *vm_region_find(struct arch_vm_region *head,
                                             unsigned long addr)
{
        struct arch_vm_region *c;

        list_for_each_entry(c, &head->vm_list, vm_list) {
                if (c->vm_start == addr)
                        goto out;
        }
        c = NULL;
out:
        return c;
}

void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
                gfp_t gfp, unsigned long attrs)
{
        struct page *page;
        struct arch_vm_region *c;
        unsigned long order;
        u64 mask = ~0ULL, limit;
        pgprot_t prot = pgprot_noncached(PAGE_KERNEL);

        if (!consistent_pte) {
                pr_err("%s: not initialized\n", __func__);
                dump_stack();
                return NULL;
        }

        if (dev) {
                mask = dev->coherent_dma_mask;

                /*
                 * Sanity check the DMA mask - it must be non-zero, and
                 * must be able to be satisfied by a DMA allocation.
                 */
                if (mask == 0) {
                        dev_warn(dev, "coherent DMA mask is unset\n");
                        goto no_page;
                }

        }

        /*
         * Sanity check the allocation size.
         */
        size = PAGE_ALIGN(size);
        limit = (mask + 1) & ~mask;
        if ((limit && size >= limit) ||
            size >= (CONSISTENT_END - CONSISTENT_BASE)) {
                pr_warn("coherent allocation too big "
                        "(requested %#x mask %#llx)\n", size, mask);
                goto no_page;
        }

        order = get_order(size);

        if (mask != 0xffffffff)
                gfp |= GFP_DMA;

        page = alloc_pages(gfp, order);
        if (!page)
                goto no_page;

        /*
         * Invalidate any data that might be lurking in the
         * kernel direct-mapped region for device DMA.
         */
        {
                unsigned long kaddr = (unsigned long)page_address(page);
                memset(page_address(page), 0, size);
                cpu_dma_wbinval_range(kaddr, kaddr + size);
        }

        /*
         * Allocate a virtual address in the consistent mapping region.
         */
        c = vm_region_alloc(&consistent_head, size,
                            gfp & ~(__GFP_DMA | __GFP_HIGHMEM));
        if (c) {
                pte_t *pte = consistent_pte + CONSISTENT_OFFSET(c->vm_start);
                struct page *end = page + (1 << order);

                c->vm_pages = page;

                /*
                 * Set the "dma handle"
                 */
                *handle = page_to_phys(page);

                do {
                        BUG_ON(!pte_none(*pte));

                        /*
                         * x86 does not mark the pages reserved...
                         */
                        SetPageReserved(page);
                        set_pte(pte, mk_pte(page, prot));
                        page++;
                        pte++;
                } while (size -= PAGE_SIZE);

                /*
                 * Free the otherwise unused pages.
                 */
                while (page < end) {
                        __free_page(page);
                        page++;
                }

                return (void *)c->vm_start;
        }

        if (page)
                __free_pages(page, order);
no_page:
        *handle = ~0;
        return NULL;
}

void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,
                dma_addr_t handle, unsigned long attrs)
{
        struct arch_vm_region *c;
        unsigned long flags, addr;
        pte_t *ptep;

        size = PAGE_ALIGN(size);

        raw_spin_lock_irqsave(&consistent_lock, flags);

        c = vm_region_find(&consistent_head, (unsigned long)cpu_addr);
        if (!c)
                goto no_area;

        if ((c->vm_end - c->vm_start) != size) {
                pr_err("%s: freeing wrong coherent size (%ld != %d)\n",
                       __func__, c->vm_end - c->vm_start, size);
                dump_stack();
                size = c->vm_end - c->vm_start;
        }

        ptep = consistent_pte + CONSISTENT_OFFSET(c->vm_start);
        addr = c->vm_start;
        do {
                pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
                unsigned long pfn;

                ptep++;
                addr += PAGE_SIZE;

                if (!pte_none(pte) && pte_present(pte)) {
                        pfn = pte_pfn(pte);

                        if (pfn_valid(pfn)) {
                                struct page *page = pfn_to_page(pfn);

                                /*
                                 * x86 does not mark the pages reserved...
                                 */
                                ClearPageReserved(page);

                                __free_page(page);
                                continue;
                        }
                }

                pr_crit("%s: bad page in kernel page table\n", __func__);
        } while (size -= PAGE_SIZE);

        flush_tlb_kernel_range(c->vm_start, c->vm_end);

        list_del(&c->vm_list);

        raw_spin_unlock_irqrestore(&consistent_lock, flags);

        kfree(c);
        return;

no_area:
        raw_spin_unlock_irqrestore(&consistent_lock, flags);
        pr_err("%s: trying to free invalid coherent area: %p\n",
               __func__, cpu_addr);
        dump_stack();
}

/*
 * Initialise the consistent memory allocation.
 */
static int __init consistent_init(void)
{
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;
        int ret = 0;

        do {
                pgd = pgd_offset(&init_mm, CONSISTENT_BASE);
                pmd = pmd_alloc(&init_mm, pgd, CONSISTENT_BASE);
                if (!pmd) {
                        pr_err("%s: no pmd tables\n", __func__);
                        ret = -ENOMEM;
                        break;
                }
                /* The first level mapping may be created in somewhere.
                 * It's not necessary to warn here. */
                /* WARN_ON(!pmd_none(*pmd)); */

                pte = pte_alloc_kernel(pmd, CONSISTENT_BASE);
                if (!pte) {
                        ret = -ENOMEM;
                        break;
                }

                consistent_pte = pte;
        } while (0);

        return ret;
}

core_initcall(consistent_init);

static inline void cache_op(phys_addr_t paddr, size_t size,
                void (*fn)(unsigned long start, unsigned long end))
{
        struct page *page = pfn_to_page(paddr >> PAGE_SHIFT);
        unsigned offset = paddr & ~PAGE_MASK;
        size_t left = size;
        unsigned long start;

        do {
                size_t len = left;

                if (PageHighMem(page)) {
                        void *addr;

                        if (offset + len > PAGE_SIZE) {
                                if (offset >= PAGE_SIZE) {
                                        page += offset >> PAGE_SHIFT;
                                        offset &= ~PAGE_MASK;
                                }
                                len = PAGE_SIZE - offset;
                        }

                        addr = kmap_atomic(page);
                        start = (unsigned long)(addr + offset);
                        fn(start, start + len);
                        kunmap_atomic(addr);
                } else {
                        start = (unsigned long)phys_to_virt(paddr);
                        fn(start, start + size);
                }
                offset = 0;
                page++;
                left -= len;
        } while (left);
}

void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
                size_t size, enum dma_data_direction dir)
{
        switch (dir) {
        case DMA_FROM_DEVICE:
                break;
        case DMA_TO_DEVICE:
        case DMA_BIDIRECTIONAL:
                cache_op(paddr, size, cpu_dma_wb_range);
                break;
        default:
                BUG();
        }
}

void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
                size_t size, enum dma_data_direction dir)
{
        switch (dir) {
        case DMA_TO_DEVICE:
                break;
        case DMA_FROM_DEVICE:
        case DMA_BIDIRECTIONAL:
                cache_op(paddr, size, cpu_dma_inval_range);
                break;
        default:
                BUG();
        }
}