drm/i915: Tidy workaround batch buffer emission

Use the "*batch++ = " style as in the ring emission for better
readability and also simplify the logic a bit by consolidating
the offset and size calculations and overflow checking. The
latter is a programming error so it is not required to check
for it after each write to the object, but rather do it once the
whole state has been written and fail the driver if something
went wrong.

v2: Rebase.

v3: Keep track of offsets and sizes in bytes for simplicity
    and rename function pointer variable to _fn suffix.
    (Chris Wilson)

v4: Fix size calc broken in v3 and add alignment warning. (Chris Wilson)

v5: Fix return code.

v6: I added an exit from loop in v5 but forgot to put back
    the object teardown.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v5)
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_lrc.c

@@ -890,18 +890,6 @@ static int execlists_request_alloc(struct drm_i915_gem_request *request)
 	return ret;
 }
 
-#define wa_ctx_emit(batch, index, cmd)					\
-	do {								\
-		int __index = (index)++;				\
-		if (WARN_ON(__index >= (PAGE_SIZE / sizeof(uint32_t)))) { \
-			return -ENOSPC;					\
-		}							\
-		batch[__index] = (cmd);					\
-	} while (0)
-
-#define wa_ctx_emit_reg(batch, index, reg) \
-	wa_ctx_emit((batch), (index), i915_mmio_reg_offset(reg))
-
 /*
  * In this WA we need to set GEN8_L3SQCREG4[21:21] and reset it after
  * PIPE_CONTROL instruction. This is required for the flush to happen correctly
@@ -918,56 +906,31 @@ static int execlists_request_alloc(struct drm_i915_gem_request *request)
  * This WA is also required for Gen9 so extracting as a function avoids
  * code duplication.
  */
-static inline int gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *engine,
-						uint32_t *batch,
-						uint32_t index)
-{
-	uint32_t l3sqc4_flush = (0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES);
-
-	wa_ctx_emit(batch, index, (MI_STORE_REGISTER_MEM_GEN8 |
-				   MI_SRM_LRM_GLOBAL_GTT));
-	wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
-	wa_ctx_emit(batch, index, i915_ggtt_offset(engine->scratch) + 256);
-	wa_ctx_emit(batch, index, 0);
-
-	wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
-	wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
-	wa_ctx_emit(batch, index, l3sqc4_flush);
-
-	wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
-	wa_ctx_emit(batch, index, (PIPE_CONTROL_CS_STALL |
-				   PIPE_CONTROL_DC_FLUSH_ENABLE));
-	wa_ctx_emit(batch, index, 0);
-	wa_ctx_emit(batch, index, 0);
-	wa_ctx_emit(batch, index, 0);
-	wa_ctx_emit(batch, index, 0);
-
-	wa_ctx_emit(batch, index, (MI_LOAD_REGISTER_MEM_GEN8 |
-				   MI_SRM_LRM_GLOBAL_GTT));
-	wa_ctx_emit_reg(batch, index, GEN8_L3SQCREG4);
-	wa_ctx_emit(batch, index, i915_ggtt_offset(engine->scratch) + 256);
-	wa_ctx_emit(batch, index, 0);
-
-	return index;
-}
-
-static inline uint32_t wa_ctx_start(struct i915_wa_ctx_bb *wa_ctx,
-				    uint32_t offset,
-				    uint32_t start_alignment)
+static u32 *
+gen8_emit_flush_coherentl3_wa(struct intel_engine_cs *engine, u32 *batch)
 {
-	return wa_ctx->offset = ALIGN(offset, start_alignment);
-}
-
-static inline int wa_ctx_end(struct i915_wa_ctx_bb *wa_ctx,
-			     uint32_t offset,
-			     uint32_t size_alignment)
-{
-	wa_ctx->size = offset - wa_ctx->offset;
-
-	WARN(wa_ctx->size % size_alignment,
-	     "wa_ctx_bb failed sanity checks: size %d is not aligned to %d\n",
-	     wa_ctx->size, size_alignment);
-	return 0;
+	*batch++ = MI_STORE_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
+	*batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
+	*batch++ = i915_ggtt_offset(engine->scratch) + 256;
+	*batch++ = 0;
+
+	*batch++ = MI_LOAD_REGISTER_IMM(1);
+	*batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
+	*batch++ = 0x40400000 | GEN8_LQSC_FLUSH_COHERENT_LINES;
+
+	*batch++ = GFX_OP_PIPE_CONTROL(6);
+	*batch++ = PIPE_CONTROL_CS_STALL | PIPE_CONTROL_DC_FLUSH_ENABLE;
+	*batch++ = 0;
+	*batch++ = 0;
+	*batch++ = 0;
+	*batch++ = 0;
+
+	*batch++ = MI_LOAD_REGISTER_MEM_GEN8 | MI_SRM_LRM_GLOBAL_GTT;
+	*batch++ = i915_mmio_reg_offset(GEN8_L3SQCREG4);
+	*batch++ = i915_ggtt_offset(engine->scratch) + 256;
+	*batch++ = 0;
+
+	return batch;
 }
 
 /*
@@ -985,42 +948,28 @@ static inline int wa_ctx_end(struct i915_wa_ctx_bb *wa_ctx,
  * MI_BATCH_BUFFER_END will be added to perctx batch and both of them together
  * makes a complete batch buffer.
  */
-static int gen8_init_indirectctx_bb(struct intel_engine_cs *engine,
-				    struct i915_wa_ctx_bb *wa_ctx,
-				    uint32_t *batch,
-				    uint32_t *offset)
+static u32 *gen8_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
 {
-	uint32_t scratch_addr;
-	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
-
 	/* WaDisableCtxRestoreArbitration:bdw,chv */
-	wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_DISABLE);
+	*batch++ = MI_ARB_ON_OFF | MI_ARB_DISABLE;
 
 	/* WaFlushCoherentL3CacheLinesAtContextSwitch:bdw */
-	if (IS_BROADWELL(engine->i915)) {
-		int rc = gen8_emit_flush_coherentl3_wa(engine, batch, index);
-		if (rc < 0)
-			return rc;
-		index = rc;
-	}
+	if (IS_BROADWELL(engine->i915))
+		batch = gen8_emit_flush_coherentl3_wa(engine, batch);
 
+	*batch++ = GFX_OP_PIPE_CONTROL(6);
+	*batch++ = PIPE_CONTROL_FLUSH_L3 | PIPE_CONTROL_GLOBAL_GTT_IVB |
+		   PIPE_CONTROL_CS_STALL | PIPE_CONTROL_QW_WRITE;
 	/* WaClearSlmSpaceAtContextSwitch:bdw,chv */
 	/* Actual scratch location is at 128 bytes offset */
-	scratch_addr = i915_ggtt_offset(engine->scratch) + 2 * CACHELINE_BYTES;
-
-	wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
-	wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
-				   PIPE_CONTROL_GLOBAL_GTT_IVB |
-				   PIPE_CONTROL_CS_STALL |
-				   PIPE_CONTROL_QW_WRITE));
-	wa_ctx_emit(batch, index, scratch_addr);
-	wa_ctx_emit(batch, index, 0);
-	wa_ctx_emit(batch, index, 0);
-	wa_ctx_emit(batch, index, 0);
+	*batch++ = i915_ggtt_offset(engine->scratch) + 2 * CACHELINE_BYTES;
+	*batch++ = 0;
+	*batch++ = 0;
+	*batch++ = 0;
 
 	/* Pad to end of cacheline */
-	while (index % CACHELINE_DWORDS)
-		wa_ctx_emit(batch, index, MI_NOOP);
+	while ((unsigned long)batch % CACHELINE_BYTES)
+		*batch++ = MI_NOOP;
 
 	/*
 	 * MI_BATCH_BUFFER_END is not required in Indirect ctx BB because
@@ -1028,7 +977,7 @@ static int gen8_init_indirectctx_bb(struct intel_engine_cs *engine,
 	 * in the register CTX_RCS_INDIRECT_CTX
 	 */
 
-	return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
+	return batch;
 }
 
 /*
@@ -1040,58 +989,38 @@ static int gen8_init_indirectctx_bb(struct intel_engine_cs *engine,
  *  This batch is terminated with MI_BATCH_BUFFER_END and so we need not add padding
  *  to align it with cacheline as padding after MI_BATCH_BUFFER_END is redundant.
  */
-static int gen8_init_perctx_bb(struct intel_engine_cs *engine,
-			       struct i915_wa_ctx_bb *wa_ctx,
-			       uint32_t *batch,
-			       uint32_t *offset)
+static u32 *gen8_init_perctx_bb(struct intel_engine_cs *engine, u32 *batch)
 {
-	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
-
 	/* WaDisableCtxRestoreArbitration:bdw,chv */
-	wa_ctx_emit(batch, index, MI_ARB_ON_OFF | MI_ARB_ENABLE);
-
-	wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);
+	*batch++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
+	*batch++ = MI_BATCH_BUFFER_END;
 
-	return wa_ctx_end(wa_ctx, *offset = index, 1);
+	return batch;
 }
 
-static int gen9_init_indirectctx_bb(struct intel_engine_cs *engine,
-				    struct i915_wa_ctx_bb *wa_ctx,
-				    uint32_t *batch,
-				    uint32_t *offset)
+static u32 *gen9_init_indirectctx_bb(struct intel_engine_cs *engine, u32 *batch)
 {
-	int ret;
-	struct drm_i915_private *dev_priv = engine->i915;
-	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
-
 	/* WaFlushCoherentL3CacheLinesAtContextSwitch:skl,bxt,glk */
-	ret = gen8_emit_flush_coherentl3_wa(engine, batch, index);
-	if (ret < 0)
-		return ret;
-	index = ret;
+	batch = gen8_emit_flush_coherentl3_wa(engine, batch);
 
 	/* WaDisableGatherAtSetShaderCommonSlice:skl,bxt,kbl,glk */
-	wa_ctx_emit(batch, index, MI_LOAD_REGISTER_IMM(1));
-	wa_ctx_emit_reg(batch, index, COMMON_SLICE_CHICKEN2);
-	wa_ctx_emit(batch, index, _MASKED_BIT_DISABLE(
-			    GEN9_DISABLE_GATHER_AT_SET_SHADER_COMMON_SLICE));
-	wa_ctx_emit(batch, index, MI_NOOP);
+	*batch++ = MI_LOAD_REGISTER_IMM(1);
+	*batch++ = i915_mmio_reg_offset(COMMON_SLICE_CHICKEN2);
+	*batch++ = _MASKED_BIT_DISABLE(
+			GEN9_DISABLE_GATHER_AT_SET_SHADER_COMMON_SLICE);
+	*batch++ = MI_NOOP;
 
 	/* WaClearSlmSpaceAtContextSwitch:kbl */
 	/* Actual scratch location is at 128 bytes offset */
-	if (IS_KBL_REVID(dev_priv, 0, KBL_REVID_A0)) {
-		u32 scratch_addr =
-			i915_ggtt_offset(engine->scratch) + 2 * CACHELINE_BYTES;
-
-		wa_ctx_emit(batch, index, GFX_OP_PIPE_CONTROL(6));
-		wa_ctx_emit(batch, index, (PIPE_CONTROL_FLUSH_L3 |
-					   PIPE_CONTROL_GLOBAL_GTT_IVB |
-					   PIPE_CONTROL_CS_STALL |
-					   PIPE_CONTROL_QW_WRITE));
-		wa_ctx_emit(batch, index, scratch_addr);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
+	if (IS_KBL_REVID(engine->i915, 0, KBL_REVID_A0)) {
+		*batch++ = GFX_OP_PIPE_CONTROL(6);
+		*batch++ = PIPE_CONTROL_FLUSH_L3 | PIPE_CONTROL_GLOBAL_GTT_IVB |
+			   PIPE_CONTROL_CS_STALL | PIPE_CONTROL_QW_WRITE;
+		*batch++ = i915_ggtt_offset(engine->scratch) +
+			   2 * CACHELINE_BYTES;
+		*batch++ = 0;
+		*batch++ = 0;
+		*batch++ = 0;
 	}
 
 	/* WaMediaPoolStateCmdInWABB:bxt,glk */
@@ -1109,41 +1038,37 @@ static int gen9_init_indirectctx_bb(struct intel_engine_cs *engine,
 		 * possible configurations, to avoid duplication they are
 		 * not shown here again.
 		 */
-		u32 eu_pool_config = 0x00777000;
-		wa_ctx_emit(batch, index, GEN9_MEDIA_POOL_STATE);
-		wa_ctx_emit(batch, index, GEN9_MEDIA_POOL_ENABLE);
-		wa_ctx_emit(batch, index, eu_pool_config);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
-		wa_ctx_emit(batch, index, 0);
+		*batch++ = GEN9_MEDIA_POOL_STATE;
+		*batch++ = GEN9_MEDIA_POOL_ENABLE;
+		*batch++ = 0x00777000;
+		*batch++ = 0;
+		*batch++ = 0;
+		*batch++ = 0;
 	}
 
 	/* Pad to end of cacheline */
-	while (index % CACHELINE_DWORDS)
-		wa_ctx_emit(batch, index, MI_NOOP);
+	while ((unsigned long)batch % CACHELINE_BYTES)
+		*batch++ = MI_NOOP;
 
-	return wa_ctx_end(wa_ctx, *offset = index, CACHELINE_DWORDS);
+	return batch;
 }
 
-static int gen9_init_perctx_bb(struct intel_engine_cs *engine,
-			       struct i915_wa_ctx_bb *wa_ctx,
-			       uint32_t *batch,
-			       uint32_t *offset)
+static u32 *gen9_init_perctx_bb(struct intel_engine_cs *engine, u32 *batch)
 {
-	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
+	*batch++ = MI_BATCH_BUFFER_END;
 
-	wa_ctx_emit(batch, index, MI_BATCH_BUFFER_END);
-
-	return wa_ctx_end(wa_ctx, *offset = index, 1);
+	return batch;
 }
 
-static int lrc_setup_wa_ctx_obj(struct intel_engine_cs *engine, u32 size)
+#define CTX_WA_BB_OBJ_SIZE (PAGE_SIZE)
+
+static int lrc_setup_wa_ctx(struct intel_engine_cs *engine)
 {
 	struct drm_i915_gem_object *obj;
 	struct i915_vma *vma;
 	int err;
 
-	obj = i915_gem_object_create(engine->i915, PAGE_ALIGN(size));
+	obj = i915_gem_object_create(engine->i915, CTX_WA_BB_OBJ_SIZE);
 	if (IS_ERR(obj))
 		return PTR_ERR(obj);
 
@@ -1165,78 +1090,70 @@ static int lrc_setup_wa_ctx_obj(struct intel_engine_cs *engine, u32 size)
 	return err;
 }
 
-static void lrc_destroy_wa_ctx_obj(struct intel_engine_cs *engine)
+static void lrc_destroy_wa_ctx(struct intel_engine_cs *engine)
 {
 	i915_vma_unpin_and_release(&engine->wa_ctx.vma);
 }
 
+typedef u32 *(*wa_bb_func_t)(struct intel_engine_cs *engine, u32 *batch);
+
 static int intel_init_workaround_bb(struct intel_engine_cs *engine)
 {
 	struct i915_ctx_workarounds *wa_ctx = &engine->wa_ctx;
-	uint32_t *batch;
-	uint32_t offset;
+	struct i915_wa_ctx_bb *wa_bb[2] = { &wa_ctx->indirect_ctx,
+					    &wa_ctx->per_ctx };
+	wa_bb_func_t wa_bb_fn[2];
 	struct page *page;
+	void *batch, *batch_ptr;
+	unsigned int i;
 	int ret;
 
-	WARN_ON(engine->id != RCS);
+	if (WARN_ON(engine->id != RCS || !engine->scratch))
+		return -EINVAL;
 
-	/* update this when WA for higher Gen are added */
-	if (INTEL_GEN(engine->i915) > 9) {
-		DRM_ERROR("WA batch buffer is not initialized for Gen%d\n",
-			  INTEL_GEN(engine->i915));
+	switch (INTEL_GEN(engine->i915)) {
+	case 9:
+		wa_bb_fn[0] = gen9_init_indirectctx_bb;
+		wa_bb_fn[1] = gen9_init_perctx_bb;
+		break;
+	case 8:
+		wa_bb_fn[0] = gen8_init_indirectctx_bb;
+		wa_bb_fn[1] = gen8_init_perctx_bb;
+		break;
+	default:
+		MISSING_CASE(INTEL_GEN(engine->i915));
 		return 0;
 	}
 
-	/* some WA perform writes to scratch page, ensure it is valid */
-	if (!engine->scratch) {
-		DRM_ERROR("scratch page not allocated for %s\n", engine->name);
-		return -EINVAL;
-	}
-
-	ret = lrc_setup_wa_ctx_obj(engine, PAGE_SIZE);
+	ret = lrc_setup_wa_ctx(engine);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Failed to setup context WA page: %d\n", ret);
 		return ret;
 	}
 
 	page = i915_gem_object_get_dirty_page(wa_ctx->vma->obj, 0);
-	batch = kmap_atomic(page);
-	offset = 0;
-
-	if (IS_GEN8(engine->i915)) {
-		ret = gen8_init_indirectctx_bb(engine,
-					       &wa_ctx->indirect_ctx,
-					       batch,
-					       &offset);
-		if (ret)
-			goto out;
-
-		ret = gen8_init_perctx_bb(engine,
-					  &wa_ctx->per_ctx,
-					  batch,
-					  &offset);
-		if (ret)
-			goto out;
-	} else if (IS_GEN9(engine->i915)) {
-		ret = gen9_init_indirectctx_bb(engine,
-					       &wa_ctx->indirect_ctx,
-					       batch,
-					       &offset);
-		if (ret)
-			goto out;
+	batch = batch_ptr = kmap_atomic(page);
 
-		ret = gen9_init_perctx_bb(engine,
-					  &wa_ctx->per_ctx,
-					  batch,
-					  &offset);
-		if (ret)
-			goto out;
+	/*
+	 * Emit the two workaround batch buffers, recording the offset from the
+	 * start of the workaround batch buffer object for each and their
+	 * respective sizes.
+	 */
+	for (i = 0; i < ARRAY_SIZE(wa_bb_fn); i++) {
+		wa_bb[i]->offset = batch_ptr - batch;
+		if (WARN_ON(!IS_ALIGNED(wa_bb[i]->offset, CACHELINE_BYTES))) {
+			ret = -EINVAL;
+			break;
 		}
+		batch_ptr = wa_bb_fn[i](engine, batch_ptr);
+		wa_bb[i]->size = batch_ptr - (batch + wa_bb[i]->offset);
+	}
+
+	BUG_ON(batch_ptr - batch > CTX_WA_BB_OBJ_SIZE);
 
-out:
 	kunmap_atomic(batch);
 	if (ret)
-		lrc_destroy_wa_ctx_obj(engine);
+		lrc_destroy_wa_ctx(engine);
 
 	return ret;
 }
@@ -1685,7 +1602,7 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *engine)
 
 	intel_engine_cleanup_common(engine);
 
-	lrc_destroy_wa_ctx_obj(engine);
+	lrc_destroy_wa_ctx(engine);
 	engine->i915 = NULL;
 	dev_priv->engine[engine->id] = NULL;
 	kfree(engine);
@@ -1971,15 +1888,14 @@ static void execlists_init_reg_state(u32 *reg_state,
 			u32 ggtt_offset = i915_ggtt_offset(wa_ctx->vma);
 
 			reg_state[CTX_RCS_INDIRECT_CTX+1] =
-				(ggtt_offset + wa_ctx->indirect_ctx.offset * sizeof(uint32_t)) |
-				(wa_ctx->indirect_ctx.size / CACHELINE_DWORDS);
+				(ggtt_offset + wa_ctx->indirect_ctx.offset) |
+				(wa_ctx->indirect_ctx.size / CACHELINE_BYTES);
 
 			reg_state[CTX_RCS_INDIRECT_CTX_OFFSET+1] =
 				intel_lr_indirect_ctx_offset(engine) << 6;
 
 			reg_state[CTX_BB_PER_CTX_PTR+1] =
-				(ggtt_offset + wa_ctx->per_ctx.offset * sizeof(uint32_t)) |
-				0x01;
+				(ggtt_offset + wa_ctx->per_ctx.offset) | 0x01;
 		}
 	}
 	reg_state[CTX_LRI_HEADER_1] = MI_LOAD_REGISTER_IMM(9) | MI_LRI_FORCE_POSTED;