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
38 void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
39 void drm_clflush_sg(struct sg_table *st);
40 void drm_clflush_virt_range(void *addr, unsigned long length);
41 bool drm_need_swiotlb(int dma_bits);
42
43
44 static 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_LOONGSON3)
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