[PATCH 2/2] drm/i915/execlists: Inhibit context save/restore for the fake preempt context

Chris Wilson chris at chris-wilson.co.uk
Tue Jan 23 16:49:38 UTC 2018


We only use the preempt context to inject an idle point into execlists.
We never need to reference its logical state, so tell the GPU never to
load it or save it.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_lrc.c | 4 ++++
 drivers/gpu/drm/i915/intel_lrc.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 22d471a4228d..c28f267a8417 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2285,6 +2285,10 @@ populate_lr_context(struct i915_gem_context *ctx,
 	if (!engine->default_state)
 		regs[CTX_CONTEXT_CONTROL + 1] |=
 			_MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT);
+	if (ctx->hw_id == PREEMPT_ID)
+		regs[CTX_CONTEXT_CONTROL + 1] |=
+			_MASKED_BIT_ENABLE(CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT |
+					   CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT);
 
 	i915_gem_object_unpin_map(ctx_obj);
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 6d4f9b995a11..e6e2c1774600 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -36,6 +36,7 @@
 #define RING_CONTEXT_CONTROL(engine)		_MMIO((engine)->mmio_base + 0x244)
 #define	  CTX_CTRL_INHIBIT_SYN_CTX_SWITCH	(1 << 3)
 #define	  CTX_CTRL_ENGINE_CTX_RESTORE_INHIBIT	(1 << 0)
+#define	  CTX_CTRL_ENGINE_CTX_SAVE_INHIBIT	(1 << 1)
 #define   CTX_CTRL_RS_CTX_ENABLE                (1 << 1)
 #define RING_CONTEXT_STATUS_BUF_BASE(engine)	_MMIO((engine)->mmio_base + 0x370)
 #define RING_CONTEXT_STATUS_BUF_LO(engine, i)	_MMIO((engine)->mmio_base + 0x370 + (i) * 8)
-- 
2.15.1



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