From e22d8e3c69a9f432b40baaaf3f894a128fdc2222 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 12 Apr 2017 12:01:11 +0100 Subject: drm/i915: Treat WC a separate cache domain When discussing a new WC mmap, we based the interface upon the assumption that GTT was fully coherent. How naive! Commits 3b5724d702ef ("drm/i915: Wait for writes through the GTT to land before reading back") and ed4596ea992d ("drm/i915/guc: WA to address the Ringbuffer coherency issue") demonstrate that writes through the GTT are indeed delayed and may be overtaken by direct WC access. To be safe, if userspace is mixing WC mmaps with other potential GTT access (pwrite, GTT mmaps) it should use set_domain(WC). Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96563 Testcase: igt/gem_pwrite/small-gtt* Testcase: igt/drv_selftest/coherency Signed-off-by: Chris Wilson Reviewed-by: Joonas Lahtinen Link: http://patchwork.freedesktop.org/patch/msgid/20170412110111.26626-2-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/selftests/i915_gem_request.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/gpu/drm/i915/selftests/i915_gem_request.c') diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_request.c b/drivers/gpu/drm/i915/selftests/i915_gem_request.c index 98b7aac41eec..6664cb2eb0b8 100644 --- a/drivers/gpu/drm/i915/selftests/i915_gem_request.c +++ b/drivers/gpu/drm/i915/selftests/i915_gem_request.c @@ -580,7 +580,7 @@ static struct i915_vma *recursive_batch(struct drm_i915_private *i915) if (err) goto err; - err = i915_gem_object_set_to_gtt_domain(obj, true); + err = i915_gem_object_set_to_wc_domain(obj, true); if (err) goto err; -- cgit v1.2.3