drm/i915: Disable FBC by default also on Haswell and later

commit 0368920e51ae0cded0eb518c340a4dd17764d461 upstream.

It causes black screen on bootup and is approximately 100x slower than
running with FBC disabled, so the GPU runs at a high frequency for much
longer - completely contrary to the power saving claims. It also still
has mutex deadlocks in multi-head scenarios, which can lead to a
system/X lockup. These bugs were known before FBC was enabled by default
on Haswell and still have not been fixed.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79716
Reported-and-tested-by: Jon Kristensen <info@jonkri.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[Jani: update subject to reflect the actual change]
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d93dcf683e8c3695960ca93c92dce87a7823d3f2..d430f2767a34e61e4009b0346c07e5d8963b9c42 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -511,8 +511,7 @@ void intel_update_fbc(struct drm_device *dev)
        obj = intel_fb->obj;
        adjusted_mode = &intel_crtc->config.adjusted_mode;
 
-       if (i915.enable_fbc < 0 &&
-           INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev)) {
+       if (i915.enable_fbc < 0) {
                if (set_no_fbc_reason(dev_priv, FBC_CHIP_DEFAULT))
                        DRM_DEBUG_KMS("disabled per chip default\n");
                goto out_disable;