drm/i915: fix long-standing SNB regression in power consumption after resume v2

commit 7dcd2677ea912573d9ed4bcd629b0023b2d11505 upstream.

This patch fixes regression in power consumtion of sandy bridge gpu, which
exists since v3.6 Sometimes after resuming from s2ram gpu starts thinking that
it's extremely busy. After that it never reaches rc6 state.

Bug exists since kernel v3.6:

commit b4ae3f22d238617ca11610b29fde16cf8c0bc6e0
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Thu Jun 14 11:04:48 2012 -0700

    drm/i915: load boot context at driver init time

For some reason RC6 is already enabled at the beginning of resuming process.
Following initliaztion breaks some internal state and confuses RPS engine.
This patch disables RC6 at the beginnig of resume and initialization.

I've rearranged initialization sequence, because intel_disable_gt_powersave()
needs initialized force_wake_get/put and some locks from the dev_priv.

Note: The culprit in the initialization sequence seems to be the write
to MBCTL added in the above mentioned commit. The first version of
this patch just held a forcewake reference across the clock gating
init functions, which seems to have been enought to gather quite a few
positive test reports. But since that smelled a bit like ad-hoc
duct-tape v2 now just disables rps/rc6 across the entire hw setup.

[danvet: Add note about v1 vs. v2 of this patch and use standard
layout for the commit citation. Also add the tested-bys from v1 and a cc:
stable.]

References https://bugs.freedesktop.org/show_bug.cgi?id=54089
References https://bugzilla.kernel.org/show_bug.cgi?id=58971
References https://patchwork.kernel.org/patch/2827634/ (patch v1)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Alexander Kaltsas <alexkaltsas@gmail.com> (v1)
Tested-by: rocko <rockorequin@hotmail.com> (v1)
Tested-by: JohnMB <johnmbryant@sky.com> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 11 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 3b315ba85a3e..d1ee611d213d 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1511,6 +1511,13 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
         dev_priv->dev = dev;
         dev_priv->info = info;
 
+        spin_lock_init(&dev_priv->irq_lock);
+        spin_lock_init(&dev_priv->gpu_error.lock);
+        spin_lock_init(&dev_priv->rps.lock);
+        mutex_init(&dev_priv->dpio_lock);
+        mutex_init(&dev_priv->rps.hw_lock);
+        mutex_init(&dev_priv->modeset_restore_lock);
+
         i915_dump_device_info(dev_priv);
 
         if (i915_get_bridge_dev(dev)) {
@@ -1602,6 +1609,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 
         intel_irq_init(dev);
         intel_gt_init(dev);
+        intel_gt_reset(dev);
 
         /* Try to make sure MCHBAR is enabled before poking at it */
         intel_setup_mchbar(dev);
@@ -1626,14 +1634,6 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
         if (!IS_I945G(dev) && !IS_I945GM(dev))
                 pci_enable_msi(dev->pdev);
 
-        spin_lock_init(&dev_priv->irq_lock);
-        spin_lock_init(&dev_priv->gpu_error.lock);
-        spin_lock_init(&dev_priv->rps.lock);
-        mutex_init(&dev_priv->dpio_lock);
-
-        mutex_init(&dev_priv->rps.hw_lock);
-        mutex_init(&dev_priv->modeset_restore_lock);
-
         dev_priv->num_plane = 1;
         if (IS_VALLEYVIEW(dev))
                 dev_priv->num_plane = 2;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 0392c288324b..60d57affc748 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4497,6 +4497,9 @@ void intel_gt_reset(struct drm_device *dev)
                 if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev))
                         __gen6_gt_force_wake_mt_reset(dev_priv);
         }
+
+        /* BIOS often leaves RC6 enabled, but disable it for hw init */
+        intel_disable_gt_powersave(dev);
 }
 
 void intel_gt_init(struct drm_device *dev)
@@ -4505,8 +4508,6 @@ void intel_gt_init(struct drm_device *dev)
 
         spin_lock_init(&dev_priv->gt_lock);
 
-        intel_gt_reset(dev);
-
         if (IS_VALLEYVIEW(dev)) {
                 dev_priv->gt.force_wake_get = vlv_force_wake_get;
                 dev_priv->gt.force_wake_put = vlv_force_wake_put;