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panfrost: Make pan_select_max_tile_size O(1)

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Separate out "calculating the size of each pixel", "selecting a tile size", and
"calculating the colour buffer allocation". Then implement the middle (selecting
a tile size) with a simple constant time expression, rather than a loop. There's
a bit of related clean up in here.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17432>
This commit is contained in:
Alyssa Rosenzweig 2022-07-12 16:45:09 -04:00 • committed by Marge Bot
parent d458384883
commit d67681c4ea
1 changed files with 31 additions and 19 deletions
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50
src/panfrost/lib/pan_cs.c
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@ -319,34 +319,37 @@ pan_bytes_per_pixel_tib(enum pipe_format format)
}
static unsigned
pan_internal_cbuf_size(const struct pan_fb_info *fb,
unsigned *tile_size)
pan_cbuf_bytes_per_pixel(const struct pan_fb_info *fb)
{
unsigned total_size = 0;
unsigned sum = 0;
*tile_size = 16 * 16;
for (int cb = 0; cb < fb->rt_count; ++cb) {
const struct pan_image_view *rt = fb->rts[cb].view;
if (!rt)
continue;
total_size += pan_bytes_per_pixel_tib(rt->format) *
rt->nr_samples * (*tile_size);
sum += pan_bytes_per_pixel_tib(rt->format) * rt->nr_samples;
}
/* We have a 4KB budget, let's reduce the tile size until it fits. */
while (total_size > 4096) {
total_size >>= 1;
*tile_size >>= 1;
}
return sum;
}
/* Align on 1k. */
total_size = ALIGN_POT(total_size, 1024);
/*
* Select the largest tile size that fits within the tilebuffer budget.
* Formally, maximize (pixels per tile) such that it is a power of two and
*
* (bytes per pixel) (pixels per tile) <= (max bytes per tile)
*
* A bit of algebra gives the following formula.
*/
static unsigned
pan_select_max_tile_size(unsigned tile_buffer_bytes, unsigned bytes_per_pixel)
{
assert(util_is_power_of_two_nonzero(tile_buffer_bytes));
assert(tile_buffer_bytes >= 1024);
/* Minimum tile size is 4x4. */
assert(*tile_size >= 4 * 4);
return total_size;
return tile_buffer_bytes >> util_logbase2_ceil(bytes_per_pixel);
}
static enum mali_color_format
@ -705,8 +708,17 @@ GENX(pan_emit_fbd)(const struct panfrost_device *dev,
pan_section_ptr(fbd, FRAMEBUFFER, LOCAL_STORAGE));
#endif
unsigned tile_size;
unsigned internal_cbuf_size = pan_internal_cbuf_size(fb, &tile_size);
unsigned bytes_per_pixel = pan_cbuf_bytes_per_pixel(fb);
unsigned tile_size = pan_select_max_tile_size(4096, bytes_per_pixel);
/* Clamp tile size to hardware limits */
tile_size = MIN2(tile_size, 16 * 16);
assert(tile_size >= 4 * 4);
/* Colour buffer allocations must be 1K aligned. */
unsigned cbuf_allocation = ALIGN_POT(bytes_per_pixel * tile_size, 1024);
assert(cbuf_allocation <= 4096 && "tile too big");
int crc_rt = GENX(pan_select_crc_rt)(fb, tile_size);
bool has_zs_crc_ext = (fb->zs.view.zs || fb->zs.view.s || crc_rt >= 0);
@ -739,7 +751,7 @@ GENX(pan_emit_fbd)(const struct panfrost_device *dev,
cfg.z_clear = fb->zs.clear_value.depth;
cfg.s_clear = fb->zs.clear_value.stencil;
cfg.color_buffer_allocation = internal_cbuf_size;
cfg.color_buffer_allocation = cbuf_allocation;
cfg.sample_count = fb->nr_samples;
cfg.sample_pattern = pan_sample_pattern(fb->nr_samples);
cfg.z_write_enable = (fb->zs.view.zs && !fb->zs.discard.z);