On Fri, 2018-10-12 at 17:33 -0700, Steve Longerbeam wrote:
>
> On 09/18/2018 02:34 AM, Philipp Zabel wrote:
>
> <snip>
> > +/*
> > + * Tile left edges are required to be aligned to multiples of 8 bytes
> > + * by the IDMAC.
> > + */
> > +static inline u32 tile_left_align(const struct ipu_image_pixfmt *fmt)
> > +{
> > + return fmt->planar ? 8 * fmt->uv_width_dec : 64 / fmt->bpp;
> > +}
>
> <snip>
>
> As I indicated, shouldn't this be
>
> return fmt->planar ? 8 * fmt->uv_width_dec : 8;
>
> ?
>
> Just from a unit analysis perspective, "64 / fmt->bp" has
> units of pixels / 8-bytes, it should have units of bytes.
The tile alignment is in pixels, not in bytes. For 16-bit and 32-bit
packed formats, we only need to align to 4 or 2 pixels, respectively,
as the LCM of 8-byte alignment and 2-byte or 4-byte pixel size is
always 8 bytes.
But now that you pointed it out, it is quite obvious that this can't
work for 24-bit packed formats. Here the LCM of 8-byte alignment and 3-
byte pixels is 24 bytes, or 8 pixels.
How about:
if (fmt->planar)
return fmt->uv_packed ? 8 : 8 * fmt->uv_width_dec;
else
return fmt->bpp == 32 ? 2 : fmt->bpp == 16 ? 4 : 8;
regards
Philipp
