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drm_cache.h revision 1.5 
      1 /*	$NetBSD: drm_cache.h,v 1.5 2021/12/18 23:45:45 riastradh Exp $	*/
      2 
      3 /**************************************************************************
      4  *
      5  * Copyright 2009 Red Hat Inc.
      6  * All Rights Reserved.
      7  *
      8  * Permission is hereby granted, free of charge, to any person obtaining a
      9  * copy of this software and associated documentation files (the
     10  * "Software"), to deal in the Software without restriction, including
     11  * without limitation the rights to use, copy, modify, merge, publish,
     12  * distribute, sub license, and/or sell copies of the Software, and to
     13  * permit persons to whom the Software is furnished to do so, subject to
     14  * the following conditions:
     15  *
     16  * The above copyright notice and this permission notice (including the
     17  * next paragraph) shall be included in all copies or substantial portions
     18  * of the Software.
     19  *
     20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     22  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
     23  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
     24  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
     25  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
     26  * USE OR OTHER DEALINGS IN THE SOFTWARE.
     27  *
     28  *
     29  **************************************************************************/
     30 /*
     31  * Authors:
     32  * Dave Airlie <airlied (at) redhat.com>
     33  */
     34 
     35 #ifndef _DRM_CACHE_H_
     36 #define _DRM_CACHE_H_
     37 
     38 #ifdef __NetBSD__
     39 #include <drm/drm_os_netbsd.h>
     40 #endif
     41 #include <linux/scatterlist.h>
     42 
     43 void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
     44 void drm_clflush_sg(struct sg_table *st);
     45 void drm_clflush_virt_range(void *addr, unsigned long length);
     46 bool drm_need_swiotlb(int dma_bits);
     47 
     48 
     49 static inline bool drm_arch_can_wc_memory(void)
     50 {
     51 #if defined(CONFIG_PPC) && !defined(CONFIG_NOT_COHERENT_CACHE)
     52 	return false;
     53 #elif defined(CONFIG_MIPS) && defined(CONFIG_CPU_LOONGSON64)
     54 	return false;
     55 #elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
     56 	/*
     57 	 * The DRM driver stack is designed to work with cache coherent devices
     58 	 * only, but permits an optimization to be enabled in some cases, where
     59 	 * for some buffers, both the CPU and the GPU use uncached mappings,
     60 	 * removing the need for DMA snooping and allocation in the CPU caches.
     61 	 *
     62 	 * The use of uncached GPU mappings relies on the correct implementation
     63 	 * of the PCIe NoSnoop TLP attribute by the platform, otherwise the GPU
     64 	 * will use cached mappings nonetheless. On x86 platforms, this does not
     65 	 * seem to matter, as uncached CPU mappings will snoop the caches in any
     66 	 * case. However, on ARM and arm64, enabling this optimization on a
     67 	 * platform where NoSnoop is ignored results in loss of coherency, which
     68 	 * breaks correct operation of the device. Since we have no way of
     69 	 * detecting whether NoSnoop works or not, just disable this
     70 	 * optimization entirely for ARM and arm64.
     71 	 */
     72 	return false;
     73 #elif defined(CONFIG_ARM) || defined(CONFIG_ARM64)
     74 	return false;
     75 #else
     76 	return true;
     77 #endif
     78 }
     79 
     80 #endif
     81