linux-kernel - [PATCH 3.2 104/200] drm/i915: Add intel_ring_cachline

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Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Daniel Vetter" <daniel.vetter@...ll.ch>,
	"Bjoern C" <lkml@...l-home.ch>,
	"Enrico Tagliavini" <enrico.tagliavini@...il.com>,
	"Chris Wilson" <chris@...is-wilson.co.uk>,
	"Ville Syrjälä" 
	<ville.syrjala@...ux.intel.com>,
	"Alexandru DAMIAN" <alexandru.damian@...el.com>
Subject: [PATCH 3.2 104/200] drm/i915: Add intel_ring_cachline_align()

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ville Syrjälä <ville.syrjala@...ux.intel.com>

commit 753b1ad4a281b0663329409d410243e91825c323 upstream.

intel_ring_cachline_align() emits MI_NOOPs until the ring tail is
aligned to a cacheline boundary.

Cc: Bjoern C <lkml@...l-home.ch>
Cc: Alexandru DAMIAN <alexandru.damian@...el.com>
Cc: Enrico Tagliavini <enrico.tagliavini@...il.com>
Suggested-by: Chris Wilson <chris@...is-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 21 +++++++++++++++++++++
 drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
 2 files changed, 22 insertions(+)

--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1213,6 +1213,27 @@ int intel_ring_begin(struct intel_ring_b
 	return 0;
 }
 
+/* Align the ring tail to a cacheline boundary */
+int intel_ring_cacheline_align(struct intel_ring_buffer *ring)
+{
+	int num_dwords = (64 - (ring->tail & 63)) / sizeof(uint32_t);
+	int ret;
+
+	if (num_dwords == 0)
+		return 0;
+
+	ret = intel_ring_begin(ring, num_dwords);
+	if (ret)
+		return ret;
+
+	while (num_dwords--)
+		intel_ring_emit(ring, MI_NOOP);
+
+	intel_ring_advance(ring);
+
+	return 0;
+}
+
 void intel_ring_advance(struct intel_ring_buffer *ring)
 {
 	ring->tail &= ring->size - 1;
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -174,6 +174,7 @@ static inline int intel_wait_ring_idle(s
 }
 
 int __must_check intel_ring_begin(struct intel_ring_buffer *ring, int n);
+int __must_check intel_ring_cacheline_align(struct intel_ring_buffer *ring);
 
 static inline void intel_ring_emit(struct intel_ring_buffer *ring,
 				   u32 data)

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