From 2286278970f2db8c2a83b02fe849e92ebf99bfaf Mon Sep 17 00:00:00 2001
From: Matthew Auld <matthew.auld@intel.com>
Date: Fri, 29 Oct 2021 13:21:37 +0100
Subject: drm/i915/dmabuf: drop the flush on discrete
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Git-commit: 57d9898bee4fa8afcde83c158b441cef634ee47c
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
We were overzealous here; even though discrete is non-LLC, it should
still be always coherent.
v2(Thomas & Daniel)
- Be extra cautious and limit to DG1
- Add some more commentary
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211029122137.3484203-1-matthew.auld@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index e8a58c997170..1b526039a60d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -248,8 +248,19 @@ static int i915_gem_object_get_pages_dmabuf(struct drm_i915_gem_object *obj)
if (IS_ERR(pages))
return PTR_ERR(pages);
- /* XXX: consider doing a vmap flush or something */
- if (!HAS_LLC(i915) || i915_gem_object_can_bypass_llc(obj))
+ /*
+ * DG1 is special here since it still snoops transactions even with
+ * CACHE_NONE. This is not the case with other HAS_SNOOP platforms. We
+ * might need to revisit this as we add new discrete platforms.
+ *
+ * XXX: Consider doing a vmap flush or something, where possible.
+ * Currently we just do a heavy handed wbinvd_on_all_cpus() here since
+ * the underlying sg_table might not even point to struct pages, so we
+ * can't just call drm_clflush_sg or similar, like we do elsewhere in
+ * the driver.
+ */
+ if (i915_gem_object_can_bypass_llc(obj) ||
+ (!HAS_LLC(i915) && !IS_DG1(i915)))
wbinvd_on_all_cpus();
sg_page_sizes = i915_sg_dma_sizes(pages->sgl);
--
2.38.1