[Nouveau] Questions on Blocklinear Mipmaps and auto-sizing

[Ilia Mirkin]

https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/drivers/nouveau/nvc0/nvc0_miptree.c#n190
On Thu, Oct 25, 2018 at 6:30 AM Fernando Sahmkow <fsahmkow27 at gmail.com> wrote:
>
> I'm currently implementing mipmaps but I have a set of troubles guessing the block height and block depth of them. According to https://envytools.readthedocs.io/en/latest/hw/memory/g80-surface.html#textures-mipmapping-and-arrays the texture unit auto resizes mipmaps' blocks but how do I know how many blocks each one uses?
>
> I'm currently using this algorithm:
>         u32 height = MipHeight(mip_level);
>         u32 gobs_in_y = (height + 7) / 8;
>         u32 bh = block_height;
>         // Magical block resizing algorithm, needs more testing.
>         while (bh > 1 && (gobs_in_y + bh - 1) / bh <= 2) {
>             bh >>= 1;
>         }
>         return bh;
> it works 95% of the time but doesn't fit the correct block size all the time. Do you guys got any info on the correct algorithm used?
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