Quoting Chris Wilson (2019-12-07 19:01:07)
> The movntqda requires 16-byte alignment for the source pointer. Avoid
> falling back to clflush if the source pointer is misaligned by doing the
> doing a small uncached memcpy to fixup the alignments.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
<SNIP>
> @@ -1150,19 +1150,30 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
> return ERR_PTR(ret);
> }
>
> + ptr = dst;
I'd add a newline here as this will propagate to the later branch if WC
map fails.
> src = ERR_PTR(-ENODEV);
> - if (src_needs_clflush &&
> - i915_can_memcpy_from_wc(NULL, offset, 0)) {
> + if (src_needs_clflush && i915_has_memcpy_from_wc()) {
> src = i915_gem_object_pin_map(src_obj, I915_MAP_WC);
> if (!IS_ERR(src)) {
> - i915_memcpy_from_wc(dst,
> - src + offset,
> - ALIGN(length, 16));
> + src += offset;
> +
> + if (!IS_ALIGNED(offset, 16)) {
> + len = min(ALIGN(offset, 16) - offset, length);
> +
> + memcpy(ptr, src, len);
> +
> + offset += len;
> + length -= len;
> + ptr += len;
> + src += len;
> + }
> + GEM_BUG_ON(!IS_ALIGNED((unsigned long)src, 16));
> +
> + i915_memcpy_from_wc(ptr, src, ALIGN(length, 16));
Could be a helper function.
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Regards, Joonas
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