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The internal ttm_bo_util memcpy uses ioremap functionality, and while it probably might be possible to use it for copying in- and out of sglist represented io memory, using io_mem_reserve() / io_mem_free() callbacks, that would cause problems with fault(). Instead, implement a method mapping page-by-page using kmap_local() semantics. As an additional benefit we then avoid the occasional global TLB flushes of ioremap() and consuming ioremap space, elimination of a critical point of failure and with a slight change of semantics we could also push the memcpy out async for testing and async driver development purposes. A special linear iomem iterator is introduced internally to mimic the old ioremap behaviour for code-paths that can't immediately be ported over. This adds to the code size and should be considered a temporary solution. Looking at the code we have a lot of checks for iomap tagged pointers. Ideally we should extend the core memremap functions to also accept uncached memory and kmap_local functionality. Then we could strip a lot of code. Cc: Christian König <christian.koenig@amd.com> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Reviewed-by: Christian König <christian.koenig@amd.com> Link: https://lore.kernel.org/r/20210602083818.241793-4-thomas.hellstrom@linux.intel.com
61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
/* SPDX-License-Identifier: MIT */
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/*
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* Copyright © 2021 Intel Corporation
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*/
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#ifndef __TTM_KMAP_ITER_H__
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#define __TTM_KMAP_ITER_H__
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#include <linux/types.h>
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struct ttm_kmap_iter;
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struct dma_buf_map;
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/**
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* struct ttm_kmap_iter_ops - Ops structure for a struct
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* ttm_kmap_iter.
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* @maps_tt: Whether the iterator maps TT memory directly, as opposed
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* mapping a TT through an aperture. Both these modes have
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* struct ttm_resource_manager::use_tt set, but the latter typically
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* returns is_iomem == true from ttm_mem_io_reserve.
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*/
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struct ttm_kmap_iter_ops {
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/**
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* kmap_local() - Map a PAGE_SIZE part of the resource using
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* kmap_local semantics.
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* @res_iter: Pointer to the struct ttm_kmap_iter representing
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* the resource.
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* @dmap: The struct dma_buf_map holding the virtual address after
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* the operation.
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* @i: The location within the resource to map. PAGE_SIZE granularity.
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*/
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void (*map_local)(struct ttm_kmap_iter *res_iter,
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struct dma_buf_map *dmap, pgoff_t i);
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/**
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* unmap_local() - Unmap a PAGE_SIZE part of the resource previously
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* mapped using kmap_local.
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* @res_iter: Pointer to the struct ttm_kmap_iter representing
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* the resource.
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* @dmap: The struct dma_buf_map holding the virtual address after
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* the operation.
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*/
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void (*unmap_local)(struct ttm_kmap_iter *res_iter,
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struct dma_buf_map *dmap);
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bool maps_tt;
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};
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/**
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* struct ttm_kmap_iter - Iterator for kmap_local type operations on a
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* resource.
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* @ops: Pointer to the operations struct.
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*
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* This struct is intended to be embedded in a resource-specific specialization
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* implementing operations for the resource.
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*
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* Nothing stops us from extending the operations to vmap, vmap_pfn etc,
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* replacing some or parts of the ttm_bo_util. cpu-map functionality.
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*/
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struct ttm_kmap_iter {
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const struct ttm_kmap_iter_ops *ops;
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};
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#endif /* __TTM_KMAP_ITER_H__ */
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