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TTM takes full control over TTM_PL_SYSTEM placed buffers. This makes driver internal usage of TTM_PL_SYSTEM prone to errors because it requires the drivers to manually handle all interactions between TTM which can swap out those buffers whenever it thinks it's the right thing to do and driver. CPU buffers which need to be fenced and shared with accelerators should be placed in driver specific placements that can explicitly handle CPU/accelerator buffer fencing. Currently, apart, from things silently failing nothing is enforcing that requirement which means that it's easy for drivers and new developers to get this wrong. To avoid the confusion we can document this requirement and clarify the solution. This came up during a discussion on dri-devel: https://lore.kernel.org/dri-devel/232f45e9-8748-1243-09bf-56763e6668b3@amd.com Signed-off-by: Zack Rusin <zackr@vmware.com> Cc: Christian König <christian.koenig@amd.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Reviewed-by: Christian König <christian.koenig@amd.com> Link: https://patchwork.freedesktop.org/patch/msgid/20211110145034.487512-1-zackr@vmware.com
101 lines
3.4 KiB
C
101 lines
3.4 KiB
C
/**************************************************************************
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*
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* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sub license, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial portions
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* of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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* USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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**************************************************************************/
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/*
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* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
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*/
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#ifndef _TTM_PLACEMENT_H_
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#define _TTM_PLACEMENT_H_
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#include <linux/types.h>
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/*
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* Memory regions for data placement.
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*
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* Buffers placed in TTM_PL_SYSTEM are considered under TTMs control and can
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* be swapped out whenever TTMs thinks it is a good idea.
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* In cases where drivers would like to use TTM_PL_SYSTEM as a valid
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* placement they need to be able to handle the issues that arise due to the
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* above manually.
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*
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* For BO's which reside in system memory but for which the accelerator
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* requires direct access (i.e. their usage needs to be synchronized
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* between the CPU and accelerator via fences) a new, driver private
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* placement that can handle such scenarios is a good idea.
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*/
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#define TTM_PL_SYSTEM 0
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#define TTM_PL_TT 1
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#define TTM_PL_VRAM 2
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#define TTM_PL_PRIV 3
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/*
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* TTM_PL_FLAG_TOPDOWN requests to be placed from the
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* top of the memory area, instead of the bottom.
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*/
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#define TTM_PL_FLAG_CONTIGUOUS (1 << 0)
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#define TTM_PL_FLAG_TOPDOWN (1 << 1)
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/* For multihop handling */
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#define TTM_PL_FLAG_TEMPORARY (1 << 2)
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/**
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* struct ttm_place
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*
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* @fpfn: first valid page frame number to put the object
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* @lpfn: last valid page frame number to put the object
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* @mem_type: One of TTM_PL_* where the resource should be allocated from.
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* @flags: memory domain and caching flags for the object
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*
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* Structure indicating a possible place to put an object.
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*/
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struct ttm_place {
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unsigned fpfn;
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unsigned lpfn;
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uint32_t mem_type;
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uint32_t flags;
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};
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/**
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* struct ttm_placement
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*
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* @num_placement: number of preferred placements
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* @placement: preferred placements
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* @num_busy_placement: number of preferred placements when need to evict buffer
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* @busy_placement: preferred placements when need to evict buffer
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*
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* Structure indicating the placement you request for an object.
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*/
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struct ttm_placement {
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unsigned num_placement;
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const struct ttm_place *placement;
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unsigned num_busy_placement;
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const struct ttm_place *busy_placement;
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};
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#endif
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