linux-kernel - Re: [PATCH v2] drm/i915: Flush untouched framebuffers before display on !llc

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Date:   Thu, 12 Jan 2017 16:24:50 -0600
From:   lkml@...garu.com
To:     Chris Wilson <chris@...is-wilson.co.uk>,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        "# v4 . 10-rc1+" <drm-intel-fixes@...ts.freedesktop.org>
Subject: Re: [PATCH v2] drm/i915: Flush untouched framebuffers before display
 on !llc

On Thu, Jan 12, 2017 at 09:17:06PM +0000, Chris Wilson wrote:
> On Mon, Jan 09, 2017 at 11:19:32AM +0000, Chris Wilson wrote:
> > On a non-llc system, the objects are created with .cache_level =
> > CACHE_NONE and so the transition to uncached for scanout is a no-op.
> > However, if the object was never written to, it will still be in the CPU
> > domain (having been zeroed out by shmemfs). Those cachelines need to be
> > flushed prior to display.
> > 
> > Reported-by: Vito Caputo
> > Fixes: a6a7cc4b7db6 ("drm/i915: Always flush the dirty CPU cache when pinning the scanout")
> > Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
> > Cc: <drm-intel-fixes@...ts.freedesktop.org> # v4.10-rc1+
> 
> Ping?

This patch fixes the problem for me, in case that's what the ping's for.

Out of curiosity the bug I reported described here be getting fixed in 4.10?
https://lists.freedesktop.org/archives/dri-devel/2017-January/128405.html

Thanks.

> 
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 76689b59fc90..bdb113ef8cfe 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3514,7 +3514,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> >  	vma->display_alignment = max_t(u64, vma->display_alignment, alignment);
> >  
> >  	/* Treat this as an end-of-frame, like intel_user_framebuffer_dirty() */
> > -	if (obj->cache_dirty) {
> > +	if (obj->cache_dirty || obj->base.write_domain == I915_GEM_DOMAIN_CPU) {
> >  		i915_gem_clflush_object(obj, true);
> >  		intel_fb_obj_flush(obj, false, ORIGIN_DIRTYFB);
> >  	}
> > -- 
> > 2.11.0
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre