From 633cf8f5056c3e72158e4dbc387b3d65926d2d55 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Mon, 3 Dec 2012 18:43:32 +0200 Subject: [PATCH] drm/i915: Don't allow ring tail to reach the same cacheline as head MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit From BSpec: "If the Ring Buffer Head Pointer and the Tail Pointer are on the same cacheline, the Head Pointer must not be greater than the Tail Pointer." The easiest way to enforce this is to reduce the reported ring space. References: Gen2 BSpec "1. Programming Environment" / 1.4.4.6 "Ring Buffer Use" Gen3 BSpec "vol1c Memory Interface Functions" / 2.3.4.5 "Ring Buffer Use" Gen4+ BSpec "vol1c Memory Interface and Command Stream" / 5.3.4.5 "Ring Buffer Use" v2: Include the exact BSpec references in the description v3: s/64/I915_RING_FREE_SPACE, and add the BSpec information to the code Signed-off-by: Ville Syrjälä Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_dma.c | 2 +- drivers/gpu/drm/i915/intel_ringbuffer.c | 4 ++-- drivers/gpu/drm/i915/intel_ringbuffer.h | 11 +++++++++++ 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c index 80ed751..8f63cd5 100644 --- a/drivers/gpu/drm/i915/i915_dma.c +++ b/drivers/gpu/drm/i915/i915_dma.c @@ -141,7 +141,7 @@ void i915_kernel_lost_context(struct drm_device * dev) ring->head = I915_READ_HEAD(ring) & HEAD_ADDR; ring->tail = I915_READ_TAIL(ring) & TAIL_ADDR; - ring->space = ring->head - (ring->tail + 8); + ring->space = ring->head - (ring->tail + I915_RING_FREE_SPACE); if (ring->space < 0) ring->space += ring->size; diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index bc7cf7c..2346b92 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -45,7 +45,7 @@ struct pipe_control { static inline int ring_space(struct intel_ring_buffer *ring) { - int space = (ring->head & HEAD_ADDR) - (ring->tail + 8); + int space = (ring->head & HEAD_ADDR) - (ring->tail + I915_RING_FREE_SPACE); if (space < 0) space += ring->size; return space; @@ -1227,7 +1227,7 @@ static int intel_ring_wait_request(struct intel_ring_buffer *ring, int n) if (request->tail == -1) continue; - space = request->tail - (ring->tail + 8); + space = request->tail - (ring->tail + I915_RING_FREE_SPACE); if (space < 0) space += ring->size; if (space >= n) { diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index d4b7416..526182e 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -1,6 +1,17 @@ #ifndef _INTEL_RINGBUFFER_H_ #define _INTEL_RINGBUFFER_H_ +/* + * Gen2 BSpec "1. Programming Environment" / 1.4.4.6 "Ring Buffer Use" + * Gen3 BSpec "vol1c Memory Interface Functions" / 2.3.4.5 "Ring Buffer Use" + * Gen4+ BSpec "vol1c Memory Interface and Command Stream" / 5.3.4.5 "Ring Buffer Use" + * + * "If the Ring Buffer Head Pointer and the Tail Pointer are on the same + * cacheline, the Head Pointer must not be greater than the Tail + * Pointer." + */ +#define I915_RING_FREE_SPACE 64 + struct intel_hw_status_page { u32 *page_addr; unsigned int gfx_addr; -- 2.7.4