linux/include/drm/drm_cache.h
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   1/**************************************************************************
   2 *
   3 * Copyright 2009 Red Hat Inc.
   4 * All Rights Reserved.
   5 *
   6 * Permission is hereby granted, free of charge, to any person obtaining a
   7 * copy of this software and associated documentation files (the
   8 * "Software"), to deal in the Software without restriction, including
   9 * without limitation the rights to use, copy, modify, merge, publish,
  10 * distribute, sub license, and/or sell copies of the Software, and to
  11 * permit persons to whom the Software is furnished to do so, subject to
  12 * the following conditions:
  13 *
  14 * The above copyright notice and this permission notice (including the
  15 * next paragraph) shall be included in all copies or substantial portions
  16 * of the Software.
  17 *
  18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  21 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  22 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  23 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  24 * USE OR OTHER DEALINGS IN THE SOFTWARE.
  25 *
  26 *
  27 **************************************************************************/
  28/*
  29 * Authors:
  30 * Dave Airlie <airlied@redhat.com>
  31 */
  32
  33#ifndef _DRM_CACHE_H_
  34#define _DRM_CACHE_H_
  35
  36#include <linux/scatterlist.h>
  37
  38void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
  39void drm_clflush_sg(struct sg_table *st);
  40void drm_clflush_virt_range(void *addr, unsigned long length);
  41bool drm_need_swiotlb(int dma_bits);
  42
  43
  44static inline bool drm_arch_can_wc_memory(void)
  45{
  46#if defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE)
  47        return false;
  48#elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON64)
  49        return false;
  50#elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
  51        /*
  52         * The DRM driver stack is designed to work with cache coherent devices
  53         * only, but permits an optimization to be enabled in some cases, where
  54         * for some buffers, both the CPU and the GPU use uncached mappings,
  55         * removing the need for DMA snooping and allocation in the CPU caches.
  56         *
  57         * The use of uncached GPU mappings relies on the correct implementation
  58         * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU
  59         * will use cached mappings nonetheless. On x86 platforms, this does not
  60         * seem to matter, as uncached CPU mappings will snoop the caches in any
  61         * case. However, on ARM and arm64, enabling this optimization on a
  62         * platform where NoSnoop is ignored results in loss of coherency, which
  63         * breaks correct operation of the device. Since we have no way of
  64         * detecting whether NoSnoop works or not, just disable this
  65         * optimization entirely for ARM and arm64.
  66         */
  67        return false;
  68#else
  69        return true;
  70#endif
  71}
  72
  73#endif
  74