[RFC] drm/amdgpu: Add macros and documentation for format modifiers.

[Marek Olšák]

On Fri, Sep 7, 2018 at 5:55 AM, Bas Nieuwenhuizen
<bas at basnieuwenhuizen.nl> wrote:
> On Fri, Sep 7, 2018 at 6:51 AM Marek Olšák <maraeo at gmail.com> wrote:
>>
>> Hopefully this answers some questions.
>>
>> Other parameters that affect tiling layouts are GB_ADDR_CONFIG (all
>> chips) and MC_ARB_RAMCFG (GFX6-8 only), and those vary with each chip.
>
> For GFX6-GFX8:
> From GB_ADDR_CONFIG addrlib only uses the pipe interleave bytes which
> are 0 (=256 bytes) for all AMDGPU HW (and on GFX9 addrlib even asserts
> on that).  From MC_ARB_RAMCFG addrlib reads the number of banks and
> ranks, calculates the number of logical banks from it, but then does
> not use it. (Presumably because it is the same number as the number of
> banks in the tiling table entry?) Some bits gets used by the kernel
> (memory row size), but those get encoded in the tile split of the
> tiling table, i.e. we do not need the separate bits.
>
> for GFX9, only the DCC meta surface seems to depend on GB_ADDR_CONFIG
> (except the aforementioned pipe interleave bytes) which are constant.

On GFX9, addrlib in Mesa uses most fields from GB_ADDR_CONFIG.
GB_ADDR_CONFIG defines the tiling formats.

On older chips, addrlib reads some fields from GB_ADDR_CONFIG and uses
the chip identification for others like the number of pipes, even
though GB_ADDR_CONFIG has the information too.

Marek