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

[Paul Berry]

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?
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