Re: [PATCH 09/10] drm/i915/dg2: Enable Wa_14014475959 - RCS / CCS context exit

John Harrison <john.c.harrison@xxxxxxxxx> · Thu, 14 Apr 2022 17:21:49 -0700

On 4/13/2022 12:27, Umesh Nerlige Ramappa wrote:
From: Matthew Brost <matthew.brost@xxxxxxxxx>

There is bug in DG2 where if the CCS contexts switches out while the RCS
is running it can cause memory corruption. To workaround this add an
atomic to a memory address with a value 1 and semaphore wait to the same
address for a value of 0. The GuC firmware is responsible for writing 0
to the memory address when it is safe for the context to switch out.

v2: Add atomic GPU instructions
v3: Add w/a number (JohnH)
v4: Set DW length to 9 atomic GPU instruction with inline data
v5: Rebase (Umesh)
v6: Split MI_ATOMIC definition into 2 (Daniele)
v7: (Daniele)
- For non-inline MI_ATOMIC, len should be 1
- Make INLINE flag part of MI_ATOMIC_INLINE definition

Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Reviewed-by: John Harrison <John.C.Harrison@xxxxxxxxx>

---
  drivers/gpu/drm/i915/gt/gen8_engine_cs.c      | 41 +++++++++++++++++++
  drivers/gpu/drm/i915/gt/intel_engine_types.h  |  8 ++++
  drivers/gpu/drm/i915/gt/intel_gpu_commands.h  |  7 ++++
  drivers/gpu/drm/i915/gt/uc/intel_guc.c        |  4 ++
  drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   |  1 +
  .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  4 ++
  6 files changed, 65 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
index 047b5a710149..9529c5455bc3 100644
--- a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
@@ -583,6 +583,43 @@ static u32 *gen12_emit_preempt_busywait(struct i915_request *rq, u32 *cs)
  	return cs;
  }
  
+/* Wa_14014475959:dg2 */
+#define CCS_SEMAPHORE_PPHWSP_OFFSET	0x540
+static u32 ccs_semaphore_offset(struct i915_request *rq)
+{
+	return i915_ggtt_offset(rq->context->state) +
+		(LRC_PPHWSP_PN * PAGE_SIZE) + CCS_SEMAPHORE_PPHWSP_OFFSET;
+}
+
+/* Wa_14014475959:dg2 */
+static u32 *ccs_emit_wa_busywait(struct i915_request *rq, u32 *cs)
+{
+	int i;
+
+	*cs++ = MI_ATOMIC_INLINE | MI_ATOMIC_GLOBAL_GTT | MI_ATOMIC_CS_STALL |
+		MI_ATOMIC_MOVE;
+	*cs++ = ccs_semaphore_offset(rq);
+	*cs++ = 0;
+	*cs++ = 1;
+
+	/*
+	 * When MI_ATOMIC_INLINE_DATA set this command must be 11 DW + (1 NOP)
+	 * to align. 4 DWs above + 8 filler DWs here.
+	 */
+	for (i = 0; i < 8; ++i)
+		*cs++ = 0;
+
+	*cs++ = MI_SEMAPHORE_WAIT |
+		MI_SEMAPHORE_GLOBAL_GTT |
+		MI_SEMAPHORE_POLL |
+		MI_SEMAPHORE_SAD_EQ_SDD;
+	*cs++ = 0;
+	*cs++ = ccs_semaphore_offset(rq);
+	*cs++ = 0;
+
+	return cs;
+}
+
  static __always_inline u32*
  gen12_emit_fini_breadcrumb_tail(struct i915_request *rq, u32 *cs)
  {
@@ -593,6 +630,10 @@ gen12_emit_fini_breadcrumb_tail(struct i915_request *rq, u32 *cs)
  	    !intel_uc_uses_guc_submission(&rq->engine->gt->uc))
  		cs = gen12_emit_preempt_busywait(rq, cs);
  
+	/* Wa_14014475959:dg2 */
+	if (intel_engine_uses_wa_hold_ccs_switchout(rq->engine))
+		cs = ccs_emit_wa_busywait(rq, cs);
+
  	rq->tail = intel_ring_offset(rq, cs);
  	assert_ring_tail_valid(rq->ring, rq->tail);
  
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index eac20112709c..298f2cc7a879 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -529,6 +529,7 @@ struct intel_engine_cs {
  #define I915_ENGINE_HAS_RCS_REG_STATE  BIT(9)
  #define I915_ENGINE_HAS_EU_PRIORITY    BIT(10)
  #define I915_ENGINE_FIRST_RENDER_COMPUTE BIT(11)
+#define I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT BIT(12)
  	unsigned int flags;
  
  	/*
@@ -629,6 +630,13 @@ intel_engine_has_relative_mmio(const struct intel_engine_cs * const engine)
  	return engine->flags & I915_ENGINE_HAS_RELATIVE_MMIO;
  }
  
+/* Wa_14014475959:dg2 */
+static inline bool
+intel_engine_uses_wa_hold_ccs_switchout(struct intel_engine_cs *engine)
+{
+	return engine->flags & I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT;
+}
+
  #define instdone_has_slice(dev_priv___, sseu___, slice___) \
  	((GRAPHICS_VER(dev_priv___) == 7 ? 1 : ((sseu___)->slice_mask)) & BIT(slice___))
  
diff --git a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
index 4243be030bc1..f3fe7d4c3234 100644
--- a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
+++ b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
@@ -134,6 +134,13 @@
  #define   MI_MEM_VIRTUAL	(1 << 22) /* 945,g33,965 */
  #define   MI_USE_GGTT		(1 << 22) /* g4x+ */
  #define MI_STORE_DWORD_INDEX	MI_INSTR(0x21, 1)
+#define MI_ATOMIC		MI_INSTR(0x2f, 1)
+#define MI_ATOMIC_INLINE	(MI_INSTR(0x2f, 9) | MI_ATOMIC_INLINE_DATA)
+#define   MI_ATOMIC_GLOBAL_GTT		(1 << 22)
+#define   MI_ATOMIC_INLINE_DATA		(1 << 18)
+#define   MI_ATOMIC_CS_STALL		(1 << 17)
+#define	  MI_ATOMIC_MOVE		(0x4 << 8)
+
  /*
   * Official intel docs are somewhat sloppy concerning MI_LOAD_REGISTER_IMM:
   * - Always issue a MI_NOOP _before_ the MI_LOAD_REGISTER_IMM - otherwise hw
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
index 830889349756..228070e31ef0 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
@@ -296,6 +296,10 @@ static u32 guc_ctl_wa_flags(struct intel_guc *guc)
  	if (IS_DG2_GRAPHICS_STEP(gt->i915, G10, STEP_A0, STEP_B0))
  		flags |= GUC_WA_GAM_CREDITS;
  
+	/* Wa_14014475959:dg2 */
+	if (IS_DG2(gt->i915))
+		flags |= GUC_WA_HOLD_CCS_SWITCHOUT;
+
  	/*
  	 * Wa_14012197797:dg2_g10:a0,dg2_g11:a0
  	 * Wa_22011391025:dg2_g10,dg2_g11,dg2_g12
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
index 126e67ea1619..e389a3a041a2 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
@@ -102,6 +102,7 @@
  #define   GUC_WA_DUAL_QUEUE		BIT(11)
  #define   GUC_WA_RCS_RESET_BEFORE_RC6	BIT(13)
  #define   GUC_WA_PRE_PARSER		BIT(14)
+#define   GUC_WA_HOLD_CCS_SWITCHOUT	BIT(17)
  #define   GUC_WA_POLLCS			BIT(18)
  
  #define GUC_CTL_FEATURE			2
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index 38ba9f783312..1cb88e99b040 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -3897,6 +3897,10 @@ static void guc_default_vfuncs(struct intel_engine_cs *engine)
  	engine->flags |= I915_ENGINE_HAS_PREEMPTION;
  	engine->flags |= I915_ENGINE_HAS_TIMESLICES;
  
+	/* Wa_14014475959:dg2 */
+	if (IS_DG2(engine->i915) && engine->class == COMPUTE_CLASS)
+		engine->flags |= I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT;
+
  	/*
  	 * TODO: GuC supports timeslicing and semaphores as well, but they're
  	 * handled by the firmware so some minor tweaks are required before







