[Nouveau] Dealing with opencl kernel parameters in nouveau now that RES support is gone

[Pierre Moreau]

Hello,

> On 22 Feb 2016, at 15:22, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> 
>> On Mon, Feb 22, 2016 at 9:17 AM, Hans de Goede <hdegoede at redhat.com> wrote:
>> Hi,
>> 
>>> On 22-02-16 14:47, Ilia Mirkin wrote:
>>> 
>>>> On Mon, Feb 22, 2016 at 8:45 AM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>>> 
>>>> INPUT is for shader inputs which come from fixed function loaders.
>>>> This is not what you want. You want CONST. Stick the input params into
>>>> a constbuf, and you're done.
>>> 
>>> 
>>> Oh, and in case it's not clear, I think this should be done by the st,
>>> not by the driver. Not a big fan of the current interface where the
>>> driver is responsible for uploading the kernel input parameters.
>> 
>> 
>> Moving this to the state-tracker will likely break clover for amd
>> cards, also what is the right place to stick the input params my
> 
> Not really. Could just have a PIPE_CAP. Could make it part of the
> whole TGSI logic in the first place. This functionality isn't used for
> the OpenGL compute shader, and it'd be nice to bring OpenCL in line
> with the OpenGL stuff.
> 
>> differ from one gpu to the other, also the opencl -> tgsi compiler
>> will need to know how to "address" input params without it needing to
>> know too much details of the targetted gpu. So of INPUT is not suitable,
>> then I think we are going to need MEMORY[#], INPUT for this, which
>> nouveau can then just treat as CONST.
> 
> That doesn't make sense... MEMORY is for... memory. Perhaps there's
> something I don't understand about kernel inputs that would make my
> suggestion unworkable? The way I see it is that you stick them into a
> user constbuf (i.e. pipe->set_constant_buffer({cb.user = pointer to
> your thing})), and then launch the grid. Your TGSI would have been
> composed such that it would expect the user params to show up in the
> first constbuf.

Apart from Tesla which uses shared memory for passing the OpenCL user params, Fermi+ use const memory for that, and this is what Samuel's patches are doing (at least from what I remember). 

Regards,
Pierre

> 
> You *really* want to be using constbufs here -- they're designed for this.
> 
>  -ilia
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