linux-kernel - [PATCH v4 1/8] drm/i915/ttm: dont trample cache

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Message-Id: <20220713133818.3699604-2-bob.beckett@collabora.com>
Date:   Wed, 13 Jul 2022 14:38:11 +0100
From:   Robert Beckett <bob.beckett@...labora.com>
To:     dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     kernel@...labora.com, Robert Beckett <bob.beckett@...labora.com>,
        Matthew Auld <matthew.auld@...el.com>,
        Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v4 1/8] drm/i915/ttm: dont trample cache_level overrides during ttm move

Various places within the driver override the default chosen cache_level.
Before ttm, these overrides were permanent until explicitly changed again
or for the lifetime of the buffer.

TTM movement code came along and decided that it could make that
decision at that time, which is usually well after object creation, so
overrode the cache_level decision and reverted it back to its default
decision.

Add logic to indicate whether the caching mode has been set by anything
other than the move logic. If so, assume that the code that overrode the
defaults knows best and keep it.

Signed-off-by: Robert Beckett <bob.beckett@...labora.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.c       | 1 +
 drivers/gpu/drm/i915/gem/i915_gem_object_types.h | 1 +
 drivers/gpu/drm/i915/gem/i915_gem_ttm.c          | 1 +
 drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c     | 9 ++++++---
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
index ccec4055fde3..966ac2d778d5 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
@@ -125,6 +125,7 @@ void i915_gem_object_set_cache_coherency(struct drm_i915_gem_object *obj,
 	struct drm_i915_private *i915 = to_i915(obj->base.dev);
 
 	obj->cache_level = cache_level;
+	obj->ttm.cache_level_override = true;
 
 	if (cache_level != I915_CACHE_NONE)
 		obj->cache_coherent = (I915_BO_CACHE_COHERENT_FOR_READ |
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
index 5cf36a130061..14937cf1daaa 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
@@ -623,6 +623,7 @@ struct drm_i915_gem_object {
 		struct i915_gem_object_page_iter get_io_page;
 		struct drm_i915_gem_object *backup;
 		bool created:1;
+		bool cache_level_override:1;
 	} ttm;
 
 	/*
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 053b0022ddd0..b6c3fc25d9d1 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -1253,6 +1253,7 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
 	i915_gem_object_init_memory_region(obj, mem);
 	i915_ttm_adjust_domains_after_move(obj);
 	i915_ttm_adjust_gem_after_move(obj);
+	obj->ttm.cache_level_override = false;
 	i915_gem_object_unlock(obj);
 
 	return 0;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
index 9a7e50534b84..042c2237e287 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -129,9 +129,12 @@ void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
 	obj->mem_flags |= i915_ttm_cpu_maps_iomem(bo->resource) ? I915_BO_FLAG_IOMEM :
 		I915_BO_FLAG_STRUCT_PAGE;
 
-	cache_level = i915_ttm_cache_level(to_i915(bo->base.dev), bo->resource,
-					   bo->ttm);
-	i915_gem_object_set_cache_coherency(obj, cache_level);
+	if (!obj->ttm.cache_level_override) {
+		cache_level = i915_ttm_cache_level(to_i915(bo->base.dev),
+						   bo->resource, bo->ttm);
+		i915_gem_object_set_cache_coherency(obj, cache_level);
+		obj->ttm.cache_level_override = false;
+	}
 }
 
 /**
-- 
2.25.1