[Mesa-dev] [PATCH 1/3] gallium: Add PIPE_COMPUTE_CAP_MAX_CONSTANT_BUFFER_SIZE

[Marek Olšák]

OpenGL 3.1 requires 4096 vec4s (65536 bytes) per constant buffer and
the hardware supports 16 constant buffers. I'm not sure what the
"constant registers" are, but they cannot have anything to do with the
constant buffer limit, because otherwise we wouldn't be able to meet
the requirement for uniform buffer objects.

Marek

On Thu, Jul 24, 2014 at 4:05 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
> On Thu, 2014-07-24 at 06:35 -0700, Tom Stellard wrote:
>> On Thu, Jul 24, 2014 at 01:09:49PM +0200, Marek Olšák wrote:
>> > Isn't this redundant with get_shader_param(PIPE_SHADER_COMPUTE,
>> > PIPE_SHADER_CAP_MAX_CONSTS) * 16?
>> >
>>
>> This is what clover was using, but I was confused about what the value
>> was supposed to represent.  Now, I think I understand (number of 4 x 32-bit
>> constants).  I can use this instead.
>
> Is the value for r600 hw misreported then? The manuals for R600/EG/NI
> say there are 512 such registers. Yet the driver reports 4096.
> See the attached patch.
>
> Jan
>
>>
>> -Tom
>> > Marek
>> >
>> > On Thu, Jul 24, 2014 at 3:05 AM, Tom Stellard <thomas.stellard at amd.com> wrote:
>> > > ---
>> > >  src/gallium/docs/source/screen.rst   | 2 ++
>> > >  src/gallium/include/pipe/p_defines.h | 3 ++-
>> > >  2 files changed, 4 insertions(+), 1 deletion(-)
>> > >
>> > > diff --git a/src/gallium/docs/source/screen.rst b/src/gallium/docs/source/screen.rst
>> > > index 830a1a5..219c9f9 100644
>> > > --- a/src/gallium/docs/source/screen.rst
>> > > +++ b/src/gallium/docs/source/screen.rst
>> > > @@ -334,6 +334,8 @@ pipe_screen::get_compute_param.
>> > >    Value type: ``uint32_t``
>> > >  * ``PIPE_COMPUTE_CAP_IMAGES_SUPPORTED``: Whether images are supported
>> > >    non-zero means yes, zero means no. Value type: ``uint32_t``
>> > > +* ``PIPE_COMPUTE_CAP_MAX_CONSTANT_BUFFER_SIZE``: The maximum size in bytes
>> > > +  of a constant buffer.  Value type: ``uint64_t``
>> > >
>> > >  .. _pipe_bind:
>> > >
>> > > diff --git a/src/gallium/include/pipe/p_defines.h b/src/gallium/include/pipe/p_defines.h
>> > > index 43bb1f5..78709b9 100644
>> > > --- a/src/gallium/include/pipe/p_defines.h
>> > > +++ b/src/gallium/include/pipe/p_defines.h
>> > > @@ -651,7 +651,8 @@ enum pipe_compute_cap
>> > >     PIPE_COMPUTE_CAP_MAX_MEM_ALLOC_SIZE,
>> > >     PIPE_COMPUTE_CAP_MAX_CLOCK_FREQUENCY,
>> > >     PIPE_COMPUTE_CAP_MAX_COMPUTE_UNITS,
>> > > -   PIPE_COMPUTE_CAP_IMAGES_SUPPORTED
>> > > +   PIPE_COMPUTE_CAP_IMAGES_SUPPORTED,
>> > > +   PIPE_COMPUTE_CAP_MAX_CONSTANT_BUFFER_SIZE
>> > >  };
>> > >
>> > >  /**
>> > > --
>> > > 1.8.1.5
>> > >
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>
> --
> Jan Vesely <jan.vesely at rutgers.edu>