Re: [PATCH 3/6] drm/nouveau: hook up cache sync functions

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Aug 28, 2013 at 06:58:37PM +0200, Lucas Stach wrote:
> Am Mittwoch, den 28.08.2013, 12:43 -0400 schrieb Konrad Rzeszutek Wilk:
> > On Wed, Aug 28, 2013 at 02:00:47AM +0200, Lucas Stach wrote:
> > > Signed-off-by: Lucas Stach <dev@lynxeye.de>
> > > ---
> > >  drivers/gpu/drm/nouveau/nouveau_bo.c  | 4 ++++
> > >  drivers/gpu/drm/nouveau/nouveau_gem.c | 5 +++++
> > >  2 files changed, 9 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > index af20fba..f4a2eb9 100644
> > > --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> > > @@ -411,6 +411,10 @@ nouveau_bo_validate(struct nouveau_bo *nvbo, bool interruptible,
> > >  {
> > >  	int ret;
> > >  
> > > +	if (nvbo->bo.ttm && nvbo->bo.ttm->caching_state == tt_cached)
> > 
> > You don't want to do it also for tt_wc ?
> > 
> No the point of using writecombined memory for BOs is to explicitly
> avoid the need for this cache sync. An uncached MMIO read from the
> device should already flush out all writecombining buffers and this read
> is always happening when submitting a pushbuf.


Could you include this explanation in the git commit description please?

> 
> > > +		ttm_dma_tt_cache_sync_for_device((struct ttm_dma_tt *)nvbo->bo.ttm,
> > > +			&nouveau_bdev(nvbo->bo.ttm->bdev)->dev->pdev->dev);
> > > +
> > >  	ret = ttm_bo_validate(&nvbo->bo, &nvbo->placement,
> > >  			      interruptible, no_wait_gpu);
> > >  	if (ret)
> > > diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > index 830cb7b..f632b92 100644
> > > --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > @@ -901,6 +901,11 @@ nouveau_gem_ioctl_cpu_prep(struct drm_device *dev, void *data,
> > >  	ret = ttm_bo_wait(&nvbo->bo, true, true, no_wait);
> > >  	spin_unlock(&nvbo->bo.bdev->fence_lock);
> > >  	drm_gem_object_unreference_unlocked(gem);
> > > +
> > > +	if (!ret && nvbo->bo.ttm && nvbo->bo.ttm->caching_state == tt_cached)
> > 
> > Ditto?
> cpu_prep is used to make the kernel aware of a following userspace read.
> Writecombined mappings are essentially uncached from the read
> perspective.
> 
> >  
> > > +		ttm_dma_tt_cache_sync_for_cpu((struct ttm_dma_tt *)nvbo->bo.ttm,
> > > +					      &dev->pdev->dev);
> > > +
> > >  	return ret;
> > >  }
> > >  
> > > -- 
> > > 1.8.3.1
> > > 
> > > _______________________________________________
> > > dri-devel mailing list
> > > dri-devel@lists.freedesktop.org
> > > http://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
>