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drm: Add a prefetching memcpy_from_wc

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Reading out of write-combining mapped memory is typically very slow
since the CPU doesn't prefetch. However some archs have special
instructions to do this.

So add a best-effort memcpy_from_wc taking dma-buf-map pointer
arguments that attempts to use a fast prefetching memcpy and
otherwise falls back to ordinary memcopies, taking the iomem tagging
into account.

The code is largely copied from i915_memcpy_from_wc.

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Christian König <christian.koenig@amd.com>
Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Link: https://lore.kernel.org/r/20210602083818.241793-5-thomas.hellstrom@linux.intel.com
Link: https://patchwork.freedesktop.org/patch/msgid/20210602083818.241793-5-thomas.hellstrom@linux.intel.com
This commit is contained in:
Thomas Hellström
2021-06-02 10:38:11 +02:00
parent 3bf3710e37
commit b7e32bef4a
4 changed files with 159 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/drm/drm_cache.h
+7
View File
@@ -35,6 +35,8 @@
#include <linux/scatterlist.h>
struct dma_buf_map;
void drm_clflush_pages(struct page *pages[], unsigned long num_pages);
void drm_clflush_sg(struct sg_table *st);
void drm_clflush_virt_range(void *addr, unsigned long length);
@@ -70,4 +72,9 @@ static inline bool drm_arch_can_wc_memory(void)
#endif
}
void drm_memcpy_init_early(void);
void drm_memcpy_from_wc(struct dma_buf_map *dst,
const struct dma_buf_map *src,
unsigned long len);
#endif