[Intel-gfx] [PATCH 3/3] drm/i915: Drop the 64k linear scanout alignment on gen2/3

[Chris Wilson]

On Thu, Jun 11, 2015 at 04:31:16PM +0300, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The docs don't support the 64k linear scanout alignment we impose
> on gen2/3. And it really makes no sense since we have no DSPSURF
> register, so the only thing that the hardware will see is the linear
> offset which will be just pixel aligned anyway.
> 
> There is one case where 64k comes into the picture, and that's FBC.
> The start of the line length buffer corresponds to a 64k aligned
> address of the uncompressed framebuffer. So if the uncompressed fb is
> not 64k aligned, the first actually used entry in the line length
> buffer will not be byte 0. There are 32 extra entries in the line
> length buffer to account for this extra alignment so we shouldn't
> have to worry about it when mapping the uncompressed fb to the GTT.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

I could not find any rationale either, and it worked this way ~10 years
ago, so
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre