[Intel-gfx] [PATCH 2/2] drm/i915: Default to mmio flips on VLV

[sourab.gupta at intel.com]

From: Sourab Gupta <sourab.gupta at intel.com>

This patch is for using mmio flips by default on VLV.
The module parameter controlling use of MMIO flips allows us to
control the default behaviour, which is set true for VLV and false
elsewhere.

Signed-off-by: Sourab Gupta <sourab.gupta at intel.com>
---
 drivers/gpu/drm/i915/i915_params.c   |  5 +++--
 drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index e0d44df..a99accc 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -48,7 +48,7 @@ struct i915_params i915 __read_mostly = {
 	.disable_display = 0,
 	.enable_cmd_parser = 1,
 	.disable_vtd_wa = 0,
-	.use_mmio_flip = 0,
+	.use_mmio_flip = -1,
 };
 
 module_param_named(modeset, i915.modeset, int, 0400);
@@ -159,4 +159,5 @@ MODULE_PARM_DESC(enable_cmd_parser,
 		 "Enable command parsing (1=enabled [default], 0=disabled)");
 
 module_param_named(use_mmio_flip, i915.use_mmio_flip, bool, 0600);
-MODULE_PARM_DESC(use_mmio_flip, "use MMIO flips (default: false)");
+MODULE_PARM_DESC(use_mmio_flip, "use MMIO page flips "
+		"(default: -1 (use per-chip default))");
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f11abfb..312a9a1 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9197,6 +9197,18 @@ static bool intel_use_mmio_flip(struct drm_device *dev)
 	if (i915.use_mmio_flip == 0)
 		return false;
 
+	/* On Valleyview, use MMIO flips by default, for Media Power Well
+	 * residency optimization. The other alternative of having Render
+	 * ring based flip calls is not being used, as the performance(FPS)
+	 * of certain 3D Apps gets severly affected.
+	 */
+	if (i915.use_mmio_flip == -1) {
+		if (IS_VALLEYVIEW(dev))
+			return true;
+		else
+			return false;
+	}
+
 	if (INTEL_INFO(dev)->gen >= 5)
 		return true;
 	else
-- 
1.8.5.1