// SPDX-License-Identifier: GPL-2.0-only
#include <linux/cpu.h>
#include <linux/dma-mapping.h>
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/export.h>
#include <linux/memblock.h>
#include <linux/of_address.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/swiotlb.h>

#include <xen/xen.h>
#include <xen/interface/grant_table.h>
#include <xen/interface/memory.h>
#include <xen/page.h>
#include <xen/swiotlb-xen.h>

#include <asm/cacheflush.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/interface.h>

unsigned long xen_get_swiotlb_free_pages(unsigned int order)
{
        struct memblock_region *reg;
        gfp_t flags = __GFP_NOWARN|__GFP_KSWAPD_RECLAIM;

        for_each_memblock(memory, reg) {
                if (reg->base < (phys_addr_t)0xffffffff) {
                        flags |= __GFP_DMA;
                        break;
                }
        }
        return __get_free_pages(flags, order);
}

enum dma_cache_op {
       DMA_UNMAP,
       DMA_MAP,
};
static bool hypercall_cflush = false;

/* functions called by SWIOTLB */

static void dma_cache_maint(dma_addr_t handle, unsigned long offset,
        size_t size, enum dma_data_direction dir, enum dma_cache_op op)
{
        struct gnttab_cache_flush cflush;
        unsigned long xen_pfn;
        size_t left = size;

        xen_pfn = (handle >> XEN_PAGE_SHIFT) + offset / XEN_PAGE_SIZE;
        offset %= XEN_PAGE_SIZE;

        do {
                size_t len = left;
        
                /* buffers in highmem or foreign pages cannot cross page
                 * boundaries */
                if (len + offset > XEN_PAGE_SIZE)
                        len = XEN_PAGE_SIZE - offset;

                cflush.op = 0;
                cflush.a.dev_bus_addr = xen_pfn << XEN_PAGE_SHIFT;
                cflush.offset = offset;
                cflush.length = len;

                if (op == DMA_UNMAP && dir != DMA_TO_DEVICE)
                        cflush.op = GNTTAB_CACHE_INVAL;
                if (op == DMA_MAP) {
                        if (dir == DMA_FROM_DEVICE)
                                cflush.op = GNTTAB_CACHE_INVAL;
                        else
                                cflush.op = GNTTAB_CACHE_CLEAN;
                }
                if (cflush.op)
                        HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);

                offset = 0;
                xen_pfn++;
                left -= len;
        } while (left);
}

static void __xen_dma_page_dev_to_cpu(struct device *hwdev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir)
{
        dma_cache_maint(handle & PAGE_MASK, handle & ~PAGE_MASK, size, dir, DMA_UNMAP);
}

static void __xen_dma_page_cpu_to_dev(struct device *hwdev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir)
{
        dma_cache_maint(handle & PAGE_MASK, handle & ~PAGE_MASK, size, dir, DMA_MAP);
}

void __xen_dma_map_page(struct device *hwdev, struct page *page,
             dma_addr_t dev_addr, unsigned long offset, size_t size,
             enum dma_data_direction dir, unsigned long attrs)
{
        if (is_device_dma_coherent(hwdev))
                return;
        if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
                return;

        __xen_dma_page_cpu_to_dev(hwdev, dev_addr, size, dir);
}

void __xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
                size_t size, enum dma_data_direction dir,
                unsigned long attrs)

{
        if (is_device_dma_coherent(hwdev))
                return;
        if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
                return;

        __xen_dma_page_dev_to_cpu(hwdev, handle, size, dir);
}

void __xen_dma_sync_single_for_cpu(struct device *hwdev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        if (is_device_dma_coherent(hwdev))
                return;
        __xen_dma_page_dev_to_cpu(hwdev, handle, size, dir);
}

void __xen_dma_sync_single_for_device(struct device *hwdev,
                dma_addr_t handle, size_t size, enum dma_data_direction dir)
{
        if (is_device_dma_coherent(hwdev))
                return;
        __xen_dma_page_cpu_to_dev(hwdev, handle, size, dir);
}

bool xen_arch_need_swiotlb(struct device *dev,
                           phys_addr_t phys,
                           dma_addr_t dev_addr)
{
        unsigned int xen_pfn = XEN_PFN_DOWN(phys);
        unsigned int bfn = XEN_PFN_DOWN(dev_addr);

        /*
         * The swiotlb buffer should be used if
         *      - Xen doesn't have the cache flush hypercall
         *      - The Linux page refers to foreign memory
         *      - The device doesn't support coherent DMA request
         *
         * The Linux page may be spanned acrros multiple Xen page, although
         * it's not possible to have a mix of local and foreign Xen page.
         * Furthermore, range_straddles_page_boundary is already checking
         * if buffer is physically contiguous in the host RAM.
         *
         * Therefore we only need to check the first Xen page to know if we
         * require a bounce buffer because the device doesn't support coherent
         * memory and we are not able to flush the cache.
         */
        return (!hypercall_cflush && (xen_pfn != bfn) &&
                !is_device_dma_coherent(dev));
}

int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
                                 unsigned int address_bits,
                                 dma_addr_t *dma_handle)
{
        if (!xen_initial_domain())
                return -EINVAL;

        /* we assume that dom0 is mapped 1:1 for now */
        *dma_handle = pstart;
        return 0;
}
EXPORT_SYMBOL_GPL(xen_create_contiguous_region);

void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
{
        return;
}
EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);

const struct dma_map_ops *xen_dma_ops;
EXPORT_SYMBOL(xen_dma_ops);

int __init xen_mm_init(void)
{
        struct gnttab_cache_flush cflush;
        if (!xen_initial_domain())
                return 0;
        xen_swiotlb_init(1, false);
        xen_dma_ops = &xen_swiotlb_dma_ops;

        cflush.op = 0;
        cflush.a.dev_bus_addr = 0;
        cflush.offset = 0;
        cflush.length = 0;
        if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
                hypercall_cflush = true;
        return 0;
}
arch_initcall(xen_mm_init);