Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Robert Beckett <bob.beckett@collabora.com>
To:     dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>
Cc:     kernel@collabora.com, Robert Beckett <bob.beckett@collabora.com>,
        Matthew Auld <matthew.auld@intel.com>,
        =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= 
        <thomas.hellstrom@linux.intel.com>, linux-kernel@vger.kernel.org
Subject: [PATCH v9 03/11] drm/i915/ttm: only trust snooping for dgfx when deciding default cache_level
Date:   Thu,  7 Jul 2022 16:35:58 +0000
Message-Id: <20220707163606.1474111-4-bob.beckett@collabora.com>
In-Reply-To: <20220707163606.1474111-1-bob.beckett@collabora.com>
References: <20220707163606.1474111-1-bob.beckett@collabora.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

By default i915_ttm_cache_level() decides I915_CACHE_LLC if HAS_SNOOP.
This is divergent from existing backends code which only considers
HAS_LLC.
Testing shows that trusting snooping on gen5- is unreliable and bsw via
ggtt mappings, so limit DGFX for now and maintain previous behaviour.

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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 4c1de0b4a10f..40249fa28a7a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c
@@ -46,7 +46,9 @@ static enum i915_cache_level
 i915_ttm_cache_level(struct drm_i915_private *i915, struct ttm_resource *res,
 		     struct ttm_tt *ttm)
 {
-	return ((HAS_LLC(i915) || HAS_SNOOP(i915)) &&
+	bool can_snoop = HAS_SNOOP(i915) && IS_DGFX(i915);
+
+	return ((HAS_LLC(i915) || can_snoop) &&
 		!i915_ttm_gtt_binds_lmem(res) &&
 		ttm->caching == ttm_cached) ? I915_CACHE_LLC :
 		I915_CACHE_NONE;
-- 
2.25.1