[Intel-gfx] [PATCH] drm/i915: flip on a no fb -> fb transition if crtc is active v3

[Jesse Barnes]

If the crtc is active, we can simply flip a new fb onto it, provided the
other mode setting reqs are met.  Otherwise, we'll need to do a full
mode set to re-enable the crtc.

v2: check for crtc active and set mode_changed accordingly
v3: add module parameter, i915.fastboot, to control no fb -> fb flip behavior

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
---
 drivers/gpu/drm/i915/i915_drv.c      |    5 +++++
 drivers/gpu/drm/i915/i915_drv.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |   12 ++++++++++--
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index a1a936f..cf266dc 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -128,6 +128,11 @@ module_param_named(disable_power_well, i915_disable_power_well, int, 0600);
 MODULE_PARM_DESC(disable_power_well,
 		 "Disable the power well when possible (default: false)");
 
+bool i915_fastboot __read_mostly = 0;
+module_param_named(fastboot, i915_fastboot, bool, 0600);
+MODULE_PARM_DESC(fastboot, "Try to skip unnecessary mode sets at boot time "
+		 "(default: false)");
+
 static struct drm_driver driver;
 extern int intel_agp_enabled;
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 62f20b2..9b9b106 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1470,6 +1470,7 @@ extern bool i915_enable_hangcheck __read_mostly;
 extern int i915_enable_ppgtt __read_mostly;
 extern unsigned int i915_preliminary_hw_support __read_mostly;
 extern int i915_disable_power_well __read_mostly;
+extern bool i915_fastboot __read_mostly;
 
 extern int i915_suspend(struct drm_device *dev, pm_message_t state);
 extern int i915_resume(struct drm_device *dev);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 80b70dc..e90df02 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8532,8 +8532,16 @@ intel_set_config_compute_mode_changes(struct drm_mode_set *set,
 	if (set->crtc->fb != set->fb) {
 		/* If we have no fb then treat it as a full mode set */
 		if (set->crtc->fb == NULL) {
-			DRM_DEBUG_KMS("crtc has no fb, full mode set\n");
-			config->mode_changed = true;
+			struct intel_crtc *intel_crtc =
+				to_intel_crtc(set->crtc);
+
+			if (intel_crtc->active && i915_fastboot) {
+				DRM_DEBUG_KMS("crtc has no fb, will flip\n");
+				config->fb_changed = true;
+			} else {
+				DRM_DEBUG_KMS("inactive crtc, full mode set\n");
+				config->mode_changed = true;
+			}
 		} else if (set->fb == NULL) {
 			config->mode_changed = true;
 		} else if (set->fb->pixel_format !=
-- 
1.7.9.5