[Mesa-dev] [PATCH 2/2] i965: Set pitch of pull constant buffers to 16.

[Eric Anholt]

On Wed, 11 Jan 2012 12:26:43 -0800, Paul Berry <stereotype441 at gmail.com> wrote:
> On 11 January 2012 12:23, Eric Anholt <eric at anholt.net> wrote:
> 
> > On Wed, 11 Jan 2012 12:06:37 -0800, Paul Berry <stereotype441 at gmail.com>
> > wrote:
> > > We always access pull constant buffers using the message types "OWord
> > > Block Read" or "OWord Dual Block Read".  According to the Sandy Bridge
> > > PRM, Vol 4 Part 1, pages 214 and 218, when using these messages:
> > >
> > >     "the surface pitch is ignored, the surface is treated as a
> > >     1-dimensional surface.  An element size (pitch) of 16 bytes is
> > >     used to determine the size of the buffer for out-of-bounds
> > >     checking if using the surface state model."
> > >
> > > Previously we were setting the pitch for pull constant buffers to the
> > > size of the whole constant buffer--this made no sense and would have
> > > led to incorrect behavior if it were not for the fact that the pitch
> > > is ignored.
> > >
> > > For clarity, this patch sets the pitch for pull constant buffers to 16
> > > bytes, consistent with the hardware's behavior.
> >
> > I'd prefer to see the 15 written as (16 - 1) just to clarify that it's a
> > value-minus-one field, similarly to how we do the
> > OUT_BATCH(_3DSTATE_CONSTANT_PS << 16 | (7 - 2)); for the length field of
> > packets.
> >
> 
> Ok, I'll do that.  Is that a "reviewed-by" with this change?

Yeah.
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