[Intel-gfx] [PATCH v4 4/6] drm/i915: consolidate LRC mode HWSP setup & teardown

[Dave Gordon]

In legacy ringbuffer mode, the HWSP is a separate GEM object with its
own pinning and reference counts. In LRC mode, however, it's not;
instead its part of the default context object. The LRC-mode setup &
teardown code therefore needs to handle this specially; the presence
of the two bugs fixed in this patchset suggests that this code is not
well-understood or maintained at present.

So, this patch:
    moves the (newly-fixed!) LRC-mode HWSP teardown code to its own
        (trivial) function lrc_teardown_hardware_status_page(), and
    changes the call signature of lrc_setup_hardware_status_page()
        to match
so that all knowledge of this special arrangement is local to these
two functions.

It will also help with efforts in progress to eliminate special
handling of the default (kernel) context elsewhere in LRC code :)

v3: Rebased

Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
---
 drivers/gpu/drm/i915/intel_lrc.c | 41 +++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 0fa2497..ff38e57 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -227,9 +227,8 @@ enum {
 
 static int intel_lr_context_pin(struct intel_context *ctx,
 				struct intel_engine_cs *engine);
-static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring,
-		struct drm_i915_gem_object *default_ctx_obj);
-
+static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring);
+static void lrc_teardown_hardware_status_page(struct intel_engine_cs *ring);
 
 /**
  * intel_sanitize_enable_execlists() - sanitize i915.enable_execlists
@@ -1555,8 +1554,7 @@ static int gen8_init_common_ring(struct intel_engine_cs *ring)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u8 next_context_status_buffer_hw;
 
-	lrc_setup_hardware_status_page(ring,
-				dev_priv->kernel_context->engine[ring->id].state);
+	lrc_setup_hardware_status_page(ring);
 
 	I915_WRITE_IMR(ring, ~(ring->irq_enable_mask | ring->irq_keep_mask));
 	I915_WRITE(RING_HWSTAM(ring->mmio_base), 0xffffffff);
@@ -2005,10 +2003,7 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *ring)
 	i915_cmd_parser_fini_ring(ring);
 	i915_gem_batch_pool_fini(&ring->batch_pool);
 
-	if (ring->status_page.obj) {
-		kunmap(kmap_to_page(ring->status_page.page_addr));
-		ring->status_page.obj = NULL;
-	}
+	lrc_teardown_hardware_status_page(ring);
 
 	ring->disable_lite_restore_wa = false;
 	ring->ctx_desc_template = 0;
@@ -2500,24 +2495,36 @@ uint32_t intel_lr_context_size(struct intel_engine_cs *ring)
 	return ret;
 }
 
-static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring,
-		struct drm_i915_gem_object *default_ctx_obj)
+static void lrc_setup_hardware_status_page(struct intel_engine_cs *ring)
 {
-	struct drm_i915_private *dev_priv = ring->dev->dev_private;
+	struct drm_i915_private *dev_priv = to_i915(ring->dev);
+	struct intel_context *dctx = dev_priv->kernel_context;
+	struct drm_i915_gem_object *dctx_obj = dctx->engine[ring->id].state;
+	u64 dctx_addr = i915_gem_obj_ggtt_offset(dctx_obj);
 	struct page *page;
 
-	/* The HWSP is part of the default context object in LRC mode. */
-	ring->status_page.gfx_addr = i915_gem_obj_ggtt_offset(default_ctx_obj)
-			+ LRC_PPHWSP_PN * PAGE_SIZE;
-	page = i915_gem_object_get_page(default_ctx_obj, LRC_PPHWSP_PN);
+	/*
+	 * The HWSP is part of the default context object in LRC mode.
+	 * Note that it doesn't contribute to the refcount!
+	 */
+	page = i915_gem_object_get_page(dctx_obj, LRC_PPHWSP_PN);
 	ring->status_page.page_addr = kmap(page);
-	ring->status_page.obj = default_ctx_obj;
+	ring->status_page.gfx_addr = dctx_addr + LRC_PPHWSP_PN * PAGE_SIZE;
+	ring->status_page.obj = dctx_obj;
 
 	I915_WRITE(RING_HWS_PGA(ring->mmio_base),
 			(u32)ring->status_page.gfx_addr);
 	POSTING_READ(RING_HWS_PGA(ring->mmio_base));
 }
 
+static void lrc_teardown_hardware_status_page(struct intel_engine_cs *ring)
+{
+	if (ring->status_page.obj) {
+		kunmap(kmap_to_page(ring->status_page.page_addr));
+		ring->status_page.obj = NULL;
+	}
+}
+
 /**
  * intel_lr_context_deferred_alloc() - create the LRC specific bits of a context
  * @ctx: LR context to create.
-- 
1.9.1