Chris Wilson <ch...@chris-wilson.co.uk> writes:
> [ text/plain ]
> The kernel context exists simply as a placeholder and should never be
> executed with a render context. It does not need the golden render
> state, as that will always be applied to a user context. By skipping the
> initialisation we can avoid issues in attempting to program the golden
> render context when trying to make the hardware idle.
>
> Testcase: igt/drm_module_reload_basic #byt
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95634
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> ---
> drivers/gpu/drm/i915/i915_gem_context.c | 45
> +++++++++++++++++++++++----------
> 1 file changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.c
> b/drivers/gpu/drm/i915/i915_gem_context.c
> index a3b11aac23a4..3e3acd054f05 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -413,7 +413,8 @@ int i915_gem_context_init(struct drm_device *dev)
> return PTR_ERR(ctx);
> }
>
> - if (!i915.enable_execlists && ctx->engine[RCS].state) {
> + if (!i915.enable_execlists) {
> + struct intel_engine_cs *engine;
> int ret;
>
> /* We may need to do things with the shrinker which
> @@ -423,13 +424,28 @@ int i915_gem_context_init(struct drm_device *dev)
> * be available. To avoid this we always pin the default
> * context.
> */
> - ret = i915_gem_obj_ggtt_pin(ctx->engine[RCS].state,
> - get_context_alignment(dev_priv), 0);
> - if (ret) {
> - DRM_ERROR("Failed to pinned default global context
> (error %d)\n",
> - ret);
> - i915_gem_context_unreference(ctx);
> - return ret;
> + for_each_engine(engine, dev_priv) {
> + struct intel_context *ce = &ctx->engine[engine->id];
> +
> + ret = 0;
> + if (ce->state)
> + ret = i915_gem_obj_ggtt_pin(ce->state,
> +
> get_context_alignment(dev_priv), 0);
> + if (ret) {
> + DRM_ERROR("Failed to pinned default global
> context (error %d)\n",
> + ret);
> + i915_gem_context_unreference(ctx);
> + return ret;
> + }
> +
> + /* The kernel context is only used as a placeholder
> + * for flushing the active context. It is never used
> + * for submitting rendering and as such never requires
> + * the golden render context, and so we can skip
> + * emitting it when we switch to the kernel context
> + * (during eviction).
> + */
> + ce->initialised = true;
My concern here is that the bdw had/has problem with entering and
exiting from rc6 with a vanilla hw state. And if you have not
submitted anything, you need a working context to sleep on.
Thus golden context was created to be that working one to sleep
and wakeup on.
-Mika
> }
> }
>
> @@ -452,13 +468,16 @@ void i915_gem_context_lost(struct drm_i915_private
> *dev_priv)
> i915_gem_context_unpin(engine->last_context, engine);
> engine->last_context = NULL;
> }
> -
> - /* Force the GPU state to be reinitialised on enabling */
> - dev_priv->kernel_context->engine[engine->id].initialised =
> - engine->init_context == NULL;
> }
>
> - /* Force the GPU state to be reinitialised on enabling */
> + /* Force the GPU state to be restore on enabling */
> + for_each_engine(engine, dev_priv) {
> + struct intel_context *ce =
> + &dev_priv->kernel_context->engine[engine->id];
> +
> + ce->initialised =
> + !i915.enable_execlists || engine->init_context == NULL;
> + }
> dev_priv->kernel_context->remap_slice = ALL_L3_SLICES(dev_priv);
> }
>
> --
> 2.8.1
>
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