On Sat, Apr 09, 2016 at 11:14:45AM +0100, Chris Wilson wrote:
> When the engine idles waiting upon a semaphore, it loses its
> pagetables and we must reload them before executing the batch.
RCS shouldn't lose them IIRC, other engines yes. As I recall the
other way to avoid this would be to prevent the engine from
entering some power save mode during the wait, but I suppose
that might come at a power cost.
>
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> ---
> drivers/gpu/drm/i915/intel_ringbuffer.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c
> b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 62d09cf2ea8f..a4bab6466388 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1446,6 +1446,7 @@ gen8_ring_sync(struct drm_i915_gem_request *waiter_req,
> {
> struct intel_engine_cs *waiter = waiter_req->engine;
> struct drm_i915_private *dev_priv = waiter->dev->dev_private;
> + struct i915_hw_ppgtt *ppgtt;
> int ret;
>
> ret = intel_ring_begin(waiter_req, 4);
> @@ -1461,6 +1462,15 @@ gen8_ring_sync(struct drm_i915_gem_request *waiter_req,
> intel_ring_emit(waiter,
> upper_32_bits(GEN8_WAIT_OFFSET(waiter, signaller->id)));
> intel_ring_advance(waiter);
> +
> + /* When the engine idles waiting upon a semaphore, it loses its
> + * pagetables and we must reload them before executing the batch.
> + * We do this on the i915_switch_context() following the wait and
> + * before the dispatch.
> + */
> + ppgtt = waiter_req->ctx->ppgtt;
> + if (ppgtt)
> + ppgtt->pd_dirty_rings |= intel_engine_flag(waiter_req->engine);
> return 0;
> }
>
> --
> 2.8.0.rc3
>
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--
Ville Syrjälä
Intel OTC
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