// SPDX-License-Identifier: GPL-2.0
/*
 * DMA operations that map physical memory directly without using an IOMMU or
 * flushing caches.
 */
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/dma-direct.h>
#include <linux/scatterlist.h>
#include <linux/dma-contiguous.h>
#include <linux/pfn.h>
#include <linux/set_memory.h>

#define DIRECT_MAPPING_ERROR            0

/*
 * Most architectures use ZONE_DMA for the first 16 Megabytes, but
 * some use it for entirely different regions:
 */
#ifndef ARCH_ZONE_DMA_BITS
#define ARCH_ZONE_DMA_BITS 24
#endif

/*
 * For AMD SEV all DMA must be to unencrypted addresses.
 */
static inline bool force_dma_unencrypted(void)
{
        return sev_active();
}

static bool
check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
                const char *caller)
{
        if (unlikely(dev && !dma_capable(dev, dma_addr, size))) {
                if (*dev->dma_mask >= DMA_BIT_MASK(32)) {
                        dev_err(dev,
                                "%s: overflow %pad+%zu of device mask %llx\n",
                                caller, &dma_addr, size, *dev->dma_mask);
                }
                return false;
        }
        return true;
}

static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
{
        dma_addr_t addr = force_dma_unencrypted() ?
                __phys_to_dma(dev, phys) : phys_to_dma(dev, phys);
        return addr + size - 1 <= dev->coherent_dma_mask;
}

void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
                gfp_t gfp, unsigned long attrs)
{
        unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
        int page_order = get_order(size);
        struct page *page = NULL;
        void *ret;

        /* we always manually zero the memory once we are done: */
        gfp &= ~__GFP_ZERO;

        /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
        if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
                gfp |= GFP_DMA;
        if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
                gfp |= GFP_DMA32;

again:
        /* CMA can be used only in the context which permits sleeping */
        if (gfpflags_allow_blocking(gfp)) {
                page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
                if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
                        dma_release_from_contiguous(dev, page, count);
                        page = NULL;
                }
        }
        if (!page)
                page = alloc_pages_node(dev_to_node(dev), gfp, page_order);

        if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
                __free_pages(page, page_order);
                page = NULL;

                if (IS_ENABLED(CONFIG_ZONE_DMA) &&
                    dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
                    !(gfp & GFP_DMA)) {
                        gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
                        goto again;
                }
        }

        if (!page)
                return NULL;
        ret = page_address(page);
        if (force_dma_unencrypted()) {
                set_memory_decrypted((unsigned long)ret, 1 << page_order);
                *dma_handle = __phys_to_dma(dev, page_to_phys(page));
        } else {
                *dma_handle = phys_to_dma(dev, page_to_phys(page));
        }
        memset(ret, 0, size);
        return ret;
}

/*
 * NOTE: this function must never look at the dma_addr argument, because we want
 * to be able to use it as a helper for iommu implementations as well.
 */
void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
                dma_addr_t dma_addr, unsigned long attrs)
{
        unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
        unsigned int page_order = get_order(size);

        if (force_dma_unencrypted())
                set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
        if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
                free_pages((unsigned long)cpu_addr, page_order);
}

static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
                unsigned long offset, size_t size, enum dma_data_direction dir,
                unsigned long attrs)
{
        dma_addr_t dma_addr = phys_to_dma(dev, page_to_phys(page)) + offset;

        if (!check_addr(dev, dma_addr, size, __func__))
                return DIRECT_MAPPING_ERROR;
        return dma_addr;
}

static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
                int nents, enum dma_data_direction dir, unsigned long attrs)
{
        int i;
        struct scatterlist *sg;

        for_each_sg(sgl, sg, nents, i) {
                BUG_ON(!sg_page(sg));

                sg_dma_address(sg) = phys_to_dma(dev, sg_phys(sg));
                if (!check_addr(dev, sg_dma_address(sg), sg->length, __func__))
                        return 0;
                sg_dma_len(sg) = sg->length;
        }

        return nents;
}

int dma_direct_supported(struct device *dev, u64 mask)
{
#ifdef CONFIG_ZONE_DMA
        if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
                return 0;
#else
        /*
         * Because 32-bit DMA masks are so common we expect every architecture
         * to be able to satisfy them - either by not supporting more physical
         * memory, or by providing a ZONE_DMA32.  If neither is the case, the
         * architecture needs to use an IOMMU instead of the direct mapping.
         */
        if (mask < DMA_BIT_MASK(32))
                return 0;
#endif
        return 1;
}

static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
{
        return dma_addr == DIRECT_MAPPING_ERROR;
}

const struct dma_map_ops dma_direct_ops = {
        .alloc                  = dma_direct_alloc,
        .free                   = dma_direct_free,
        .map_page               = dma_direct_map_page,
        .map_sg                 = dma_direct_map_sg,
        .dma_supported          = dma_direct_supported,
        .mapping_error          = dma_direct_mapping_error,
        .is_phys                = 1,
};
EXPORT_SYMBOL(dma_direct_ops);