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

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Mon, 2021-05-24 at 17:45 +0100, Matthew Auld wrote:
> 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>

Hmm, you're right. I'll fix. Thanks for reviewing!

/Thomas


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