So is the summary that currently MMIO flips do not work on some platforms?
That could be a problem because the scheduler is intended to be enabled
for everything and thus will be forcing MMIO flips on everything. So
should I reverse the logic here - only enable the scheduler if MMIO
flips are already enabled?
Thanks,
John.
On 22/02/2016 09:41, Lankhorst, Maarten wrote:
Hey,
Jesse Barnes schreef op vr 19-02-2016 om 12:01 [-0800]:
On 02/19/2016 11:53 AM, Ville Syrjälä wrote:
On Fri, Feb 19, 2016 at 11:28:05AM -0800, Jesse Barnes wrote:
On 02/18/2016 06:26 AM, John.C.Harrison@xxxxxxxxx wrote:
From: John Harrison <John.C.Harrison@xxxxxxxxx>
MMIO flips are the preferred mechanism now but more importantly, pipe
based flips cause issues for the scheduler. Specifically, submitting
work to the rings around the side of the scheduler could cause that
work to be lost if the scheduler generates a pre-emption event on that
ring.
For: VIZ-1587
Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_display.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 6e12ed7..731d20a 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -46,6 +46,7 @@
#include <linux/dma_remapping.h>
#include <linux/reservation.h>
#include <linux/dma-buf.h>
+#include "i915_scheduler.h"
/* Primary plane formats for gen <= 3 */
static const uint32_t i8xx_primary_formats[] = {
@@ -11330,6 +11331,8 @@ static bool use_mmio_flip(struct intel_engine_cs *ring,
return true;
else if (i915.enable_execlists)
return true;
+ else if (i915_scheduler_is_enabled(ring->dev))
+ return true;
else if (obj->base.dma_buf &&
!reservation_object_test_signaled_rcu(obj->base.dma_buf->resv,
false))
Why can't we use mmio flips unconditionally? Maarten or Ville?
We do when execlists are used, which is always on gen9+. So I guess I'm
missing the point of this patch. For gen5+ we could also do it trivially.
didn't check if the scheduler is also enabled for gen8 (I guess it would be nice, that would cover BDW and BSW).
I have a patch that would enable support for mmio flips on all
platforms, but because of Chris Wilson's objections I still didn't force
mmio flips by default.
For older platforms it'd require a bit of work since we'd need to
complete the flips from the vblank interrupt. Well, we actually do
that already even with CS flips on those platforms, but we do look
at the flip pending interrupt to figure out if CS already issued
the flip or not. So that part would need changing.
It was easy to fix in a way similar to that.
I also think we should switch to using the vblank interrupt for this
stuff on all platforms, mainly since the flip done interrupt is somewhat
broken on at least BDW (no idea if it got fixed in SKL or later), and
doing things in more than one way certainly won't decrease our bug count.
Yeah that's probably the way to go; I haven't checked the behavior on SKL either.
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