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| author | Thomas Hellström <thomas.hellstrom@linux.intel.com> | 2021-06-02 11:38:11 +0300 |
|---|---|---|
| committer | Thomas Hellström <thomas.hellstrom@linux.intel.com> | 2021-06-07 17:07:08 +0300 |
| commit | b7e32bef4ae5f9149276203564b7911fac466588 (patch) | |
| tree | b8752329b4d43041fe4837a322cf684513bd697d /Documentation/i2c/dma-considerations.rst | |
| parent | 3bf3710e3718a5aebdf465343bc1125b6e8cca96 (diff) | |
| download | linux-b7e32bef4ae5f9149276203564b7911fac466588.tar.xz | |
drm: Add a prefetching memcpy_from_wc
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
Diffstat (limited to 'Documentation/i2c/dma-considerations.rst')
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