From 27d5385c289671e85b7705af9abaeb594cf2d45d Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 21 May 2013 13:18:58 +0100 Subject: [PATCH] drm/i915: Workaround incoherence with fence updates on Valleyview In commit 25ff1195f8a0b3724541ae7bbe331b4296de9c06 Author: Chris Wilson Date: Thu Apr 4 21:31:03 2013 +0100 drm/i915: Workaround incoherence between fences and LLC across multiple CPUs we introduced an empirical workaround for memory corruption when using fences from multiple CPUs. At the time, we did not have any results for Valleyview, so the presumption was that it was limited to recent generations using LLC. Now we have evidence that Valleyview also suffers incoherence and requires a similar but different workaround. For Valleyview, the wbinvd instruction is insufficient and we require the serialising register write per-CPU. Conversely, that serialising register write is not enough for SNB/IVB/HSW. To compromise and keep the code relatively clean, employ both serialisation techniques in the same workaround. Reported-by: Jon Bloomfield Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62191 Signed-off-by: Chris Wilson --- drivers/gpu/drm/i915/i915_gem.c | 35 ++++++++++++++++++++++++++++------- 1 file changed, 28 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 38c8f11..0c6f0bd 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2711,18 +2711,33 @@ static inline int fence_number(struct drm_i915_private *dev_priv, return fence - dev_priv->fence_regs; } +struct write_fence { + struct drm_device *dev; + struct drm_i915_gem_object *obj; + int fence; +}; + static void i915_gem_write_fence__ipi(void *data) { + struct write_fence *args = data; + + /* Required for SNB+ with LLC */ wbinvd(); + + /* Required for VLV */ + i915_gem_write_fence(args->dev, args->fence, args->obj); } static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj, struct drm_i915_fence_reg *fence, bool enable) { - struct drm_device *dev = obj->base.dev; - struct drm_i915_private *dev_priv = dev->dev_private; - int fence_reg = fence_number(dev_priv, fence); + struct drm_i915_private *dev_priv = obj->base.dev->dev_private; + struct write_fence args = { + .dev = obj->base.dev, + .fence = fence_number(dev_priv, fence), + .obj = enable ? obj : NULL, + }; /* In order to fully serialize access to the fenced region and * the update to the fence register we need to take extreme @@ -2733,13 +2748,19 @@ static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj, * SNB+ we need to take a step further and emit an explicit wbinvd() * on each processor in order to manually flush all memory * transactions before updating the fence register. + * + * However, Valleyview complicates matter. There the wbinvd is + * insufficient and unlike SNB/IVB requires the serialising + * register write. (Note that that register write by itself is + * conversely not sufficient for SNB+.) To compromise, we do both. */ - if (HAS_LLC(obj->base.dev)) - on_each_cpu(i915_gem_write_fence__ipi, NULL, 1); - i915_gem_write_fence(dev, fence_reg, enable ? obj : NULL); + if (INTEL_INFO(args.dev)->gen >= 6) + on_each_cpu(i915_gem_write_fence__ipi, &args, 1); + else + i915_gem_write_fence(args.dev, args.fence, args.obj); if (enable) { - obj->fence_reg = fence_reg; + obj->fence_reg = args.fence; fence->obj = obj; list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list); } else { -- 1.7.10.4