[PATCH] radeon: fix pitch alignment for non-power-of-two mipmaps on SI

[Marek Olšák]

BTW, the intuitive explanation of the fix is that we have to minify
the pitch (or POT width) instead of the NPOT width.

Marek

On Thu, Sep 19, 2013 at 6:37 PM, Marek Olšák <maraeo at gmail.com> wrote:
> On Thu, Sep 19, 2013 at 4:41 PM, Michel Dänzer <michel at daenzer.net> wrote:
>> On Don, 2013-09-19 at 14:33 +0200, Marek Olšák wrote:
>>> This fixes VM protection faults.
>>>
>>> I have a new piglit test which can iterate over all possible widths, heights,
>>> and depths (including NPOT) and tests mipmapping with various texture targets.
>>>
>>> After this is committed, I'll make a new release of libdrm and bump
>>> the libdrm version requirement in Mesa.
>>> ---
>>>  radeon/radeon_surface.c | 14 +++++++++++---
>>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/radeon/radeon_surface.c b/radeon/radeon_surface.c
>>> index 1710e34..d5c45c4 100644
>>> --- a/radeon/radeon_surface.c
>>> +++ b/radeon/radeon_surface.c
>>> @@ -1412,7 +1412,11 @@ static void si_surf_minify(struct radeon_surface *surf,
>>>                             uint32_t xalign, uint32_t yalign, uint32_t zalign,
>>>                             uint32_t slice_align, unsigned offset)
>>>  {
>>> -    surflevel->npix_x = mip_minify(surf->npix_x, level);
>>> +    if (level == 0) {
>>> +        surflevel->npix_x = surf->npix_x;
>>> +    } else {
>>> +        surflevel->npix_x = mip_minify(next_power_of_two(surf->npix_x), level);
>>> +    }
>>>      surflevel->npix_y = mip_minify(surf->npix_y, level);
>>>      surflevel->npix_z = mip_minify(surf->npix_z, level);
>>>
>>
>> Shouldn't this be done (only) for nblk_x instead of npix_x?
>
> First, level[i].npix_x/y/z have misleading names, because they are
> always aligned to a power of two for non-zero mipmap levels, therefore
> Mesa shouldn't use them in place of u_minify, because it's not the
> same thing. In fact, r600g doesn't really use them and even though
> radeonsi does, they are incorrectly used in place of u_minify. It's on
> my TODO list.
>
> mip_minify is defined as: level ? MAX2(1, next_power_of_two(x >> level)) : x.
> u_minify is defined as: level ? MAX2(1, x >> level) : x.
>
> Considering that probably nothing in Mesa uses level[i].npix_x/y/z
> correctly, it's not so important what the variables contain.
>
> The problem this patch fixes is that next_power_of_two should be
> applied before the minification, like this: next_power_of_two(x) >>
> level. I had to guess it and test it thoroughly. The memory addressing
> documentation is pretty useless here.
>
> Marek