[Intel-gfx] [PATCH] drm/i915: Use true PPGTT in Gen8 if execlists are enabled

[Daniel Vetter]

On Mon, Dec 15, 2014 at 12:47:14PM +0000, Michel Thierry wrote:
> On 12/15/2014 10:11 AM, Daniel Vetter wrote:
> >On Thu, Dec 11, 2014 at 12:07:18PM +0000, Michel Thierry wrote:
> >>When execlists submission is enabled, try full ppgtt by default.
> >>
> >>Note, this patch considers that execlist support has been enabled by
> >>default on Gen8.
> >>
> >>Signed-off-by: Michel Thierry <michel.thierry at intel.com>
> >>---
> >>  drivers/gpu/drm/i915/i915_gem_gtt.c | 9 ++++++---
> >>  1 file changed, 6 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> >>index 171f6ea..4ed3904 100644
> >>--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> >>+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> >>@@ -40,8 +40,8 @@ static int sanitize_enable_ppgtt(struct drm_device *dev, int enable_ppgtt)
> >>  	has_aliasing_ppgtt = INTEL_INFO(dev)->gen >= 6;
> >>  	has_full_ppgtt = INTEL_INFO(dev)->gen >= 7;
> >>-	if (IS_GEN8(dev))
> >>-		has_full_ppgtt = false; /* XXX why? */
> >>+	if (IS_GEN8(dev) && !i915.enable_execlists)
> >>+		has_full_ppgtt = false; /* Only enforce with execlists */
> >Imo this has outlived it's usefulness - enable_ppgtt is an unsafe
> >parameter so everyone setting it themselves gets what they need.
> >Afair this was just because of the execlist depency on gen8 for ppgtt.
> >-Daniel
> Not sure if I'm following you up on this...
> The aim was to change the default value to _full_ only when execlists are
> also enable (after Thomas' patch).  In gen8, we don't want to have full
> ppgtt with legacy ring submission.

Yeah I gotten confused. The comment is a bit misleading thought, maybe
"Full ppgtt needs execlist since otherwise the ctx switch can hang"?
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch