drm_cache.h

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 *
 * Copyright 2009 Red Hat Inc.
 * All Rights Reserved.
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/*
 * Authors:
 * Dave Airlie <airlied@redhat.com>
 */
 
#ifndef _DRM_CACHE_H_
#define _DRM_CACHE_H_
 
#include <linux/scatterlist.h>
 
struct iosys_map;
 
void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
void drm_clflush_sg(struct sg_table *st);
void drm_clflush_virt_range(void *addr, unsigned long length);
bool drm_need_swiotlb(int dma_bits);
 
 
static inline bool drm_arch_can_wc_memory(void)
{
#if defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE)
    return false;
#elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON64)
    return false;
#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
    /*
     * The DRM driver stack is designed to work with cache coherent devices
     * only, but permits an optimization to be enabled in some cases, where
     * for some buffers, both the CPU and the GPU use uncached mappings,
     * removing the need for DMA snooping and allocation in the CPU caches.
     *
     * The use of uncached GPU mappings relies on the correct implementation
     * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU
     * will use cached mappings nonetheless. On x86 platforms, this does not
     * seem to matter, as uncached CPU mappings will snoop the caches in any
     * case. However, on ARM and arm64, enabling this optimization on a
     * platform where NoSnoop is ignored results in loss of coherency, which
     * breaks correct operation of the device. Since we have no way of
     * detecting whether NoSnoop works or not, just disable this
     * optimization entirely for ARM and arm64.
     */
    return false;
#elif defined(CONFIG_LOONGARCH)
    /*
     * LoongArch maintains cache coherency in hardware, but its WUC attribute
     * (Weak-ordered UnCached, which is similar to WC) is out of the scope of
     * cache coherency machanism. This means WUC can only used for write-only
     * memory regions.
     */
    return false;
#else
    return true;
#endif
}
 
void drm_memcpy_init_early(void);
 
void drm_memcpy_from_wc(struct iosys_map *dst,
            const struct iosys_map *src,
            unsigned long len);
#endif