Re: [igt-dev] [PATCH i-g-t 1/2] lib/igt_fb: Don't use blitter for large buffers

Chris Wilson
2019-03-28T18:25:20Z

Quoting Ville Syrjala (2019-03-28 17:54:49)
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The blitter stride is limited to <32k. Fall back to gtt mmap or
> rendercopy if we're about to exceed that.
>
> Not quite sure why we're not just using gtt mmap for Y tiling
> always. But let's keep it like that for now.
>
> v2: Use rendercopy as the fallback for Yf
>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> lib/igt_fb.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/lib/igt_fb.c b/lib/igt_fb.c
> index fcd7c4c5d187..8b6adf55a338 100644
> --- a/lib/igt_fb.c
> +++ b/lib/igt_fb.c
> @@ -1502,6 +1502,20 @@ struct fb_blit_upload {
> struct intel_batchbuffer *batch;
> };
>
> +static bool use_rendercopy(const struct igt_fb *fb)
> +{
> + return is_ccs_modifier(fb->modifier) ||
> + (fb->modifier == I915_FORMAT_MOD_Yf_TILED &&
> + fb->strides[0] >= 32768);

And probably wise to assert <= 256k.

> +
> +static bool use_blitter(const struct igt_fb *fb)
> +{
> + return (fb->modifier == I915_FORMAT_MOD_Y_TILED ||
> + fb->modifier == I915_FORMAT_MOD_Yf_TILED) &&
> + fb->strides[0] < 32768;

32k dwords is the limit for tiled blits (on gen4+). I presume strides[]
is in bytes.
-Chris