Re: [PATCH] BDW swizzling

[Ben Widawsky <benjamin.widawsky@intel.com>]

On Thu, Apr 10, 2014 at 05:24:07PM +0100, Damien Lespiau wrote:
> While cruising through the specs, I noticed a note about swizzling changes on
> BDW. My understanding is that we don't need to either initialize swizzling on
> the GPU side nor swizzle the address ourselves on the CPU side.
> 
> That could be totally wrong though, and I unfortunately don't have a machine to
> test this theory on.

I fought with this too. My resolution was we can either set all the
swizzling bits, or set none. There is no motivation to do either, and
the spec simply is telling us what they do for windows. That was well
over a year ago, so it all can be different now.

I honestly don't care what we do though, so long as the patches get
tested both in simulation and silicon, and there is no measurable perf
drop. I suppose my mild preference is to, "don't touch it if it ain't
broke."

Sorry, but at the moment, I don't have time to test this for you. Maybe
someone else can, or remind me in a couple of weeks.

> 
> -- 
> Damien
> 
> Damien Lespiau (1):
>   drm/i915/bdw: BDW swizzling in done by the memory controller
> 
>  drivers/gpu/drm/i915/i915_gem.c        |  2 --
>  drivers/gpu/drm/i915/i915_gem_tiling.c | 10 +++++++++-
>  drivers/gpu/drm/i915/i915_reg.h        |  1 -
>  3 files changed, 9 insertions(+), 4 deletions(-)
> 
> -- 
> 1.8.3.1
> 

-- 
Ben Widawsky, Intel Open Source Technology Center