Re: [Intel-gfx] [PATCH v3 07/12] drm, drm/i915: Move the memcpy_from_wc functionality to core drm

[Matthew Auld <matthew.william.auld@gmail.com>]

On Fri, 21 May 2021 at 16:33, Thomas Hellström
<thomas.hellstrom@linux.intel.com> wrote:
>
> Memcpy from wc will be used as well by TTM memcpy.
> Move it to core drm, and make the interface do the right thing
> even on !X86.
>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Dave Airlie <airlied@gmail.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---

<snip>

> +
> +#ifdef CONFIG_X86
> +bool drm_memcpy_from_wc(void *dst, const void *src, unsigned long len);
> +bool drm_memcpy_from_wc_dbm(struct dma_buf_map *dst,
> +                           const struct dma_buf_map *src,
> +                           unsigned long len);
> +void drm_unaligned_memcpy_from_wc(void *dst, const void *src, unsigned long len);
> +
> +/* The movntdqa instructions used for memcpy-from-wc require 16-byte alignment,
> + * as well as SSE4.1 support. drm_memcpy_from_wc() will report if it cannot
> + * perform the operation. To check beforehand, pass in the parameters to
> + * drm_can_memcpy_from_wc() - since we only care about the low 4 bits,
> + * you only need to pass in the minor offsets, page-aligned pointers are
> + * always valid.
> + *
> + * For just checking for SSE4.1, in the foreknowledge that the future use
> + * will be correctly aligned, just use drm_has_memcpy_from_wc().
> + */
> +#define drm_can_memcpy_from_wc(dst, src, len) \
> +       drm_memcpy_from_wc((void *)((unsigned long)(dst) | (unsigned long)(src) | (len)), NULL, 0)
> +
> +#define drm_has_memcpy_from_wc() \
> +       drm_memcpy_from_wc(NULL, NULL, 0)
> +
> +void drm_memcpy_init_early(void);
> +
> +#else
> +
> +#define drm_memcpy_from_wc(_dst, _src, _len) (false)
> +#define drm_memcpy_from_wc_dbm(_dst, _src, _len) (false)
> +#define drm_can_memcpy_from_wc(_dst, _src, _len) (false)
> +#define drm_has_memcpy_from_wc() (false)

Does the compiler not complain for these on !x86, if called without
checking the result of the statement? Maybe just make these function
stubs?

Otherwise,
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

> +#define drm_unaligned_memcpy_from_wc(_dst, _src, _len) WARN_ON(1)
> +#define drm_memcpy_init_early() do {} while (0)
> +#endif /* CONFIG_X86 */
> +#endif /* __DRM_MEMCPY_H__ */
> --
> 2.31.1
>
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