[PATCH] drm/radeon: Disable writeback by default on ppc

[Michel Dänzer]

On Don, 2013-12-05 at 12:39 +1100, Benjamin Herrenschmidt wrote:
> On Wed, 2013-12-04 at 19:05 -0500, Alex Deucher wrote:
> 
> > > Setting CP_RB_CNTL.BUF_SWAP causes the CP to use the selected byte
> > > swapping for just about everything accessed by the CP (rptr writeback,
> > > indirect buffers, etc.).  Looks like the DMA ring supports and enables
> > > rptr writeback as well (DMA_RB_CNTL.DMA_RPTR_WRITEBACK_SWAP_ENABLE) so
> > > I think we can drop the swapping of the rptr writeback.
> > >
> > 
> > Obvious patch attached.
> 
> This works all the way back to r300 ?

I don't think so, as I have writeback working without this patch on the
RV350 in this PowerBook. So I think this function needs to be split,
probably between R600 and older.

Also, there's more code at least potentially affected by this, e.g. in: 

      * cik_compute_ring_get_rptr(), cik_compute_ring_get_wptr(),
        cik_compute_ring_set_wptr(), cik_get_ih_wptr()
      * si_get_ih_wptr()
      * evergreen_get_ih_wptr()
      * r600_get_ih_wptr()
      * radeon_fence_write(), radeon_fence_read()
      * radeon_ring_backup()


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer