[Intel-gfx] [PATCH 1/3] drm/i915: Use readl/writel for ring buffer access

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

We know ringbuffers are memory and not ports so if we use readl
and writel instead of ioread32 and iowrite32 (which dispatch to
the very same functions after checking the address range) we
avoid generating functions calls and branching on every access.

This generates smaller code and potentialy also improves
performance. Brief testing with gem_latency (ten runs of both
-n 0 and -n 100) show potential 3% better throughput and 1%
better latency although more runs would be required to be
absolutely certain.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c         | 8 ++++----
 drivers/gpu/drm/i915/intel_lrc.c        | 2 +-
 drivers/gpu/drm/i915/intel_lrc.h        | 2 +-
 drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +-
 drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 247d962afabb..d9c003225d8e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2907,7 +2907,7 @@ semaphore_waits_for(struct intel_engine_cs *engine, u32 *seqno)
 		head &= engine->buffer->size - 1;
 
 		/* This here seems to blow up */
-		cmd = ioread32(engine->buffer->virtual_start + head);
+		cmd = readl(engine->buffer->virtual_start + head);
 		if (cmd == ipehr)
 			break;
 
@@ -2917,11 +2917,11 @@ semaphore_waits_for(struct intel_engine_cs *engine, u32 *seqno)
 	if (!i)
 		return NULL;
 
-	*seqno = ioread32(engine->buffer->virtual_start + head + 4) + 1;
+	*seqno = readl(engine->buffer->virtual_start + head + 4) + 1;
 	if (INTEL_INFO(engine->dev)->gen >= 8) {
-		offset = ioread32(engine->buffer->virtual_start + head + 12);
+		offset = readl(engine->buffer->virtual_start + head + 12);
 		offset <<= 32;
-		offset = ioread32(engine->buffer->virtual_start + head + 8);
+		offset = readl(engine->buffer->virtual_start + head + 8);
 	}
 	return semaphore_wait_to_signaller_ring(engine, ipehr, offset);
 }
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 5e08ea5aa6d1..3c2dd448b446 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -822,7 +822,7 @@ static void __wrap_ring_buffer(struct intel_ringbuffer *ringbuf)
 	virt = ringbuf->virtual_start + ringbuf->tail;
 	rem /= 4;
 	while (rem--)
-		iowrite32(MI_NOOP, virt++);
+		writel(MI_NOOP, virt++);
 
 	ringbuf->tail = 0;
 	intel_ring_update_space(ringbuf);
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 9affda2c650c..eeec4bc19bac 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -82,7 +82,7 @@ static inline void intel_logical_ring_advance(struct intel_ringbuffer *ringbuf)
 static inline void intel_logical_ring_emit(struct intel_ringbuffer *ringbuf,
 					   u32 data)
 {
-	iowrite32(data, ringbuf->virtual_start + ringbuf->tail);
+	writel(data, ringbuf->virtual_start + ringbuf->tail);
 	ringbuf->tail += 4;
 }
 static inline void intel_logical_ring_emit_reg(struct intel_ringbuffer *ringbuf,
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 19ebe7796e7f..d336a9de8a09 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2344,7 +2344,7 @@ static void __wrap_ring_buffer(struct intel_ringbuffer *ringbuf)
 	virt = ringbuf->virtual_start + ringbuf->tail;
 	rem /= 4;
 	while (rem--)
-		iowrite32(MI_NOOP, virt++);
+		writel(MI_NOOP, virt++);
 
 	ringbuf->tail = 0;
 	intel_ring_update_space(ringbuf);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 2ade194bbea9..bd821e443ac9 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -444,7 +444,7 @@ static inline void intel_ring_emit(struct intel_engine_cs *engine,
 				   u32 data)
 {
 	struct intel_ringbuffer *ringbuf = engine->buffer;
-	iowrite32(data, ringbuf->virtual_start + ringbuf->tail);
+	writel(data, ringbuf->virtual_start + ringbuf->tail);
 	ringbuf->tail += 4;
 }
 static inline void intel_ring_emit_reg(struct intel_engine_cs *engine,
-- 
1.9.1